{"id":4477,"date":"2026-09-22T13:07:46","date_gmt":"2026-09-22T13:07:46","guid":{"rendered":"https:\/\/mywarmhome.co.uk\/stage\/?page_id=4477"},"modified":"2026-10-11T14:47:24","modified_gmt":"2026-10-11T14:47:24","slug":"glossary-2","status":"publish","type":"page","link":"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/","title":{"rendered":"glossary"},"content":{"rendered":"\n<div class=\"wp-block-cover alignfull has-parallax\" style=\"margin-top:0;margin-bottom:0;padding-top:clamp(70px,9vw,130px);padding-right:clamp(22px,5vw,80px);padding-bottom:clamp(70px,9vw,130px);padding-left:clamp(22px,5vw,80px);min-height:30vw;aspect-ratio:unset;\"><div class=\"wp-block-cover__image-background wp-image-3905 size-full has-parallax\" style=\"background-position:50% 50%;background-image:url(https:\/\/mywarmhome.co.uk\/stage\/wp-content\/uploads\/2026\/09\/cpd1.png)\"><\/div><span aria-hidden=\"true\" class=\"wp-block-cover__background has-background-dim-50 has-background-dim\" style=\"background-color:#134558\"><\/span><div class=\"wp-block-cover__inner-container has-global-padding is-layout-constrained wp-container-core-cover-is-layout-84b4e035 wp-block-cover-is-layout-constrained\">\n<p class=\"has-text-color wp-block-paragraph\" style=\"color:#f29a3f;margin-bottom:16px;font-size:14px;font-style:normal;font-weight:800;letter-spacing:0.14em;text-transform:uppercase\">MyWarmHome Glossary<\/p>\n\n\n\n<h1 class=\"wp-block-heading has-text-color\" style=\"color:#fffaf2;margin-top:0;margin-bottom:22px;font-size:clamp(48px,8vw,112px);font-weight:800;letter-spacing:-0.035em;line-height:0.9;text-transform:uppercase\">What does<br>that mean?<\/h1>\n\n\n\n<p class=\"has-text-color wp-block-paragraph\" style=\"color:#ffffffdf;margin-top:0;margin-bottom:0;font-size:clamp(20px,2.4vw,32px);font-weight:600;line-height:1.2\">Retrofit without the jargon.<\/p>\n<\/div><\/div>\n\n\n\n<div class=\"wp-block-group alignfull has-text-color has-background has-global-padding is-layout-constrained wp-container-core-group-is-layout-5b325647 wp-block-group-is-layout-constrained\" style=\"color:#17313a;background-color:#fffaf2;margin-top:0;margin-bottom:0;padding-top:clamp(50px,7vw,90px);padding-right:clamp(22px,5vw,80px);padding-bottom:18px;padding-left:clamp(22px,5vw,80px)\">\n<p class=\"has-text-color wp-block-paragraph\" style=\"color:#f29a3f;margin-bottom:14px;font-size:14px;font-weight:800;letter-spacing:0.12em;text-transform:uppercase\">Plain English first<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" style=\"margin-top:0;margin-bottom:22px;font-size:clamp(34px,4.6vw,58px);font-weight:760;letter-spacing:-0.02em;line-height:1.02\">Retrofit has enough acronyms already.<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"margin-bottom:14px;font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.49), 19px);line-height:1.65\">Search a term, jump to a letter or choose a topic. Definitions are written for homeowners first, with the technical meaning kept intact.<\/p>\n\n\n\n<p class=\"has-text-color wp-block-paragraph\" style=\"color:#53676f;margin-bottom:0;font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.196), 16px);line-height:1.6\"><strong>Look out for dotted terms around MyWarmHome.<\/strong> Hover with a mouse, tab to them with a keyboard, or tap on a phone for a quick explanation without leaving the page.<\/p>\n<\/div>\n\n\n\n<div class=\"wp-block-group alignfull has-background has-global-padding is-layout-constrained wp-container-core-group-is-layout-60145d7e wp-block-group-is-layout-constrained\" style=\"background-color:#fffaf2;margin-top:0;margin-bottom:0;padding-top:0;padding-right:0;padding-bottom:0;padding-left:0\">\t\t<section class=\"mwh-glossary\" data-mwh-glossary>\n\t\t\t<div class=\"mwh-glossary__tools\">\n\t\t\t\t<p class=\"mwh-glossary__intro\">A clearer word for it. Search a term or abbreviation, then open an entry for the meaning, a practical example and connected ideas.<\/p>\n\t\t\t\t<div class=\"mwh-glossary__filter-row\">\n\t\t\t\t\t<div class=\"mwh-glossary__search-wrap\"><label for=\"mwh-glossary-search\">Find a word or phrase<\/label><input id=\"mwh-glossary-search\" type=\"search\" placeholder=\"Try heat loss, damp or kWh\u2026\" autocomplete=\"off\"><\/div>\n\t\t\t\t\t<div><label for=\"mwh-glossary-topic\">Explore a topic<\/label><select id=\"mwh-glossary-topic\"><option value=\"all\">All topics<\/option><option value=\"building-fabric-insulation\">Building Fabric &amp; Insulation<\/option><option value=\"controls\">Controls<\/option><option value=\"energy-performance\">Energy &amp; Performance<\/option><option value=\"heating-hot-water\">Heating &amp; Hot Water<\/option><option value=\"moisture-damp\">Moisture &amp; Damp<\/option><option value=\"renewables-electricity\">Renewables &amp; Electricity<\/option><option value=\"retrofit-standards\">Retrofit &amp; Standards<\/option><option value=\"ventilation-air-quality\">Ventilation &amp; Air Quality<\/option><\/select><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<nav class=\"mwh-glossary__alphabet\" aria-label=\"Filter glossary by letter\"><button type=\"button\" class=\"is-active\" data-letter=\"all\" aria-pressed=\"true\">All<\/button><button type=\"button\" data-letter=\"A\" aria-pressed=\"false\" >A<\/button><button type=\"button\" data-letter=\"B\" aria-pressed=\"false\" >B<\/button><button type=\"button\" data-letter=\"C\" aria-pressed=\"false\" >C<\/button><button type=\"button\" data-letter=\"D\" aria-pressed=\"false\" >D<\/button><button type=\"button\" data-letter=\"E\" aria-pressed=\"false\" >E<\/button><button type=\"button\" data-letter=\"F\" aria-pressed=\"false\" >F<\/button><button type=\"button\" data-letter=\"G\" aria-pressed=\"false\" >G<\/button><button type=\"button\" data-letter=\"H\" aria-pressed=\"false\" >H<\/button><button type=\"button\" data-letter=\"I\" aria-pressed=\"false\" >I<\/button><button type=\"button\" data-letter=\"J\" aria-pressed=\"false\" >J<\/button><button type=\"button\" data-letter=\"K\" aria-pressed=\"false\" >K<\/button><button type=\"button\" data-letter=\"L\" aria-pressed=\"false\" >L<\/button><button type=\"button\" data-letter=\"M\" aria-pressed=\"false\" >M<\/button><button type=\"button\" data-letter=\"N\" aria-pressed=\"false\" >N<\/button><button type=\"button\" data-letter=\"O\" aria-pressed=\"false\" >O<\/button><button type=\"button\" data-letter=\"P\" aria-pressed=\"false\" >P<\/button><button type=\"button\" data-letter=\"Q\" aria-pressed=\"false\" >Q<\/button><button type=\"button\" data-letter=\"R\" aria-pressed=\"false\" >R<\/button><button type=\"button\" data-letter=\"S\" aria-pressed=\"false\" >S<\/button><button type=\"button\" data-letter=\"T\" aria-pressed=\"false\" >T<\/button><button type=\"button\" data-letter=\"U\" aria-pressed=\"false\" >U<\/button><button type=\"button\" data-letter=\"V\" aria-pressed=\"false\" >V<\/button><button type=\"button\" data-letter=\"W\" aria-pressed=\"false\" >W<\/button><button type=\"button\" data-letter=\"X\" aria-pressed=\"false\" >X<\/button><button type=\"button\" data-letter=\"Y\" aria-pressed=\"false\"  disabled='disabled'>Y<\/button><button type=\"button\" data-letter=\"Z\" aria-pressed=\"false\" >Z<\/button><\/nav>\n\t\t\t\t<div class=\"mwh-glossary__results\"><p class=\"mwh-glossary__count\" aria-live=\"polite\">192 terms<\/p><button type=\"button\" data-mwh-glossary-reset>Clear filters<\/button><\/div>\n\t\t\t<\/div>\n\t\t\t<div class=\"mwh-dictionary\" role=\"region\" aria-label=\"Home retrofit thesaurus\">\n\t\t\t\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"A\" aria-labelledby=\"mwh-letter-A\"><h2 id=\"mwh-letter-A\" class=\"mwh-dictionary-letter\">A<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-air-changes-per-hour\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"A\" data-categories=\"ventilation-air-quality\" data-search=\"Air Changes per Hour ACH ACH The number of times the air inside a room or building is replaced in one hour. The number of times the air inside a room or building is replaced in one hour. It is used when looking at ventilation, air quality and heat loss.Also called: ACHIn more detailThis compares airflow with the size of the space. It can describe intentional ventilation or leakage measured under test conditions; the test conditions must be stated before comparing figures.A practical exampleA 50 cubic metre room receiving 50 cubic metres of fresh air each hour has one air change per hour.Related termsThese are connected ideas, rather than always exact synonyms.Ventilation RateAir Tightness Test\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Air Changes per Hour <span class=\"mwh-entry-acronym\">ACH<\/span><\/span><span class=\"mwh-entry-short\">The number of times the air inside a room or building is replaced in one hour.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The number of times the air inside a room or building is replaced in one hour. It is used when looking at ventilation, air quality and heat loss.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> ACH<\/p><h3>In more detail<\/h3><p>This compares airflow with the size of the space. It can describe intentional ventilation or leakage measured under test conditions; the test conditions must be stated before comparing figures.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A 50 cubic metre room receiving 50 cubic metres of fresh air each hour has one air change per hour.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ventilation-rate\" data-mwh-related=\"ventilation-rate\">Ventilation Rate<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-tightness-test\" data-mwh-related=\"air-tightness-test\">Air Tightness Test<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-changes-per-hour\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-air-permeability\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"A\" data-categories=\"building-fabric-insulation\" data-search=\"Air Permeability   A measure of how much air leaks through the gaps and cracks in a building. A measure of how much air leaks through the gaps and cracks in a building. Lower air permeability usually means a more airtight home.In more detailUsually expressed as cubic metres of air leaking per hour per square metre of building envelope at a stated pressure. A lower test result means fewer unintended leaks, but says nothing by itself about adequate fresh-air provision.A practical exampleTwo similar homes may need different ventilation improvements even if their leakage-test scores match.Related termsThese are connected ideas, rather than always exact synonyms.Air TightnessAir Tightness Test\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Air Permeability<\/span><span class=\"mwh-entry-short\">A measure of how much air leaks through the gaps and cracks in a building.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A measure of how much air leaks through the gaps and cracks in a building. Lower air permeability usually means a more airtight home.<\/p><h3>In more detail<\/h3><p>Usually expressed as cubic metres of air leaking per hour per square metre of building envelope at a stated pressure. A lower test result means fewer unintended leaks, but says nothing by itself about adequate fresh-air provision.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Two similar homes may need different ventilation improvements even if their leakage-test scores match.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-tightness\" data-mwh-related=\"air-tightness\">Air Tightness<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-tightness-test\" data-mwh-related=\"air-tightness-test\">Air Tightness Test<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-permeability\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-air-source-heat-pump\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"A\" data-categories=\"heating-hot-water\" data-search=\"Air Source Heat Pump ASHP ASHP A low-carbon heating system that takes heat from the outside air and upgrades it to heat the home and hot water. A low-carbon heating system that takes heat from the outside air and upgrades it to heat the home and hot water.Also called: ASHPIn more detailUses electricity to move heat from outdoor air into the home, even when the air feels cold. Air-to-water systems serve radiators or underfloor heating; air-to-air systems blow warmed air indoors. Good sizing and controls matter.A practical exampleA correctly designed air-to-water system can replace a boiler while using suitable existing or upgraded radiators.Related termsThese are connected ideas, rather than always exact synonyms.Heat PumpDesign Flow Temperature\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Air Source Heat Pump <span class=\"mwh-entry-acronym\">ASHP<\/span><\/span><span class=\"mwh-entry-short\">A low-carbon heating system that takes heat from the outside air and upgrades it to heat the home and hot water.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A low-carbon heating system that takes heat from the outside air and upgrades it to heat the home and hot water.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> ASHP<\/p><h3>In more detail<\/h3><p>Uses electricity to move heat from outdoor air into the home, even when the air feels cold. Air-to-water systems serve radiators or underfloor heating; air-to-air systems blow warmed air indoors. Good sizing and controls matter.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A correctly designed air-to-water system can replace a boiler while using suitable existing or upgraded radiators.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-pump\" data-mwh-related=\"heat-pump\">Heat Pump<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-design-flow-temperature\" data-mwh-related=\"design-flow-temperature\">Design Flow Temperature<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-source-heat-pump\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-air-tightness\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"A\" data-categories=\"controls\" data-search=\"Air Tightness  Airtightness How well a building prevents uncontrolled draughts and air leakage. How well a building prevents uncontrolled draughts and air leakage. Good airtightness helps reduce heat loss but must be balanced with suitable ventilation.Also called: AirtightnessIn more detailDescribes control of unintended air movement through the building fabric. It differs from ventilation, which deliberately supplies and removes air. Sealing leaks should therefore be planned alongside extraction and fresh-air provision.A practical exampleSealing around a pipe penetration reduces a draught; blocking a required air vent removes ventilation.Related termsThese are connected ideas, rather than always exact synonyms.Draught ProofingVentilation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Air Tightness<\/span><span class=\"mwh-entry-short\">How well a building prevents uncontrolled draughts and air leakage.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">How well a building prevents uncontrolled draughts and air leakage. Good airtightness helps reduce heat loss but must be balanced with suitable ventilation.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> Airtightness<\/p><h3>In more detail<\/h3><p>Describes control of unintended air movement through the building fabric. It differs from ventilation, which deliberately supplies and removes air. Sealing leaks should therefore be planned alongside extraction and fresh-air provision.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Sealing around a pipe penetration reduces a draught; blocking a required air vent removes ventilation.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-draught-proofing\" data-mwh-related=\"draught-proofing\">Draught Proofing<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ventilation\" data-mwh-related=\"ventilation\">Ventilation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-tightness\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-air-tightness-test\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"A\" data-categories=\"building-fabric-insulation\" data-search=\"Air Tightness Test  Airtightness Test A pressure test used to measure how leaky a building is. A pressure test used to measure how leaky a building is. A fan is usually fitted into a doorway to pressurise or depressurise the property.Also called: Airtightness TestIn more detailA specialist temporarily fits a fan and measures airflow at controlled pressure differences. Results help locate leakage and quantify it. This is not the same as measuring normal day-to-day ventilation with windows and fans in use.A practical exampleSmoke tracing during a test may reveal a leak around a loft hatch.Related termsThese are connected ideas, rather than always exact synonyms.Air PermeabilityService Penetration\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Air Tightness Test<\/span><span class=\"mwh-entry-short\">A pressure test used to measure how leaky a building is.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A pressure test used to measure how leaky a building is. A fan is usually fitted into a doorway to pressurise or depressurise the property.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> Airtightness Test<\/p><h3>In more detail<\/h3><p>A specialist temporarily fits a fan and measures airflow at controlled pressure differences. Results help locate leakage and quantify it. This is not the same as measuring normal day-to-day ventilation with windows and fans in use.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Smoke tracing during a test may reveal a leak around a loft hatch.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-permeability\" data-mwh-related=\"air-permeability\">Air Permeability<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-service-penetration\" data-mwh-related=\"service-penetration\">Service Penetration<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-tightness-test\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-ambient-temperature\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"A\" data-categories=\"heating-hot-water\" data-search=\"Ambient Temperature   The surrounding air temperature. The surrounding air temperature. In heating, this often means the outside air temperature.In more detailMeans the temperature of the air surrounding the item being discussed. Always check whether a specification means outdoor air, room air or a plant-room temperature; this changes how equipment performance should be interpreted.A practical exampleA heat pump&#039;s output at a mild outdoor temperature may differ from its output on a freezing morning.Related termsThese are connected ideas, rather than always exact synonyms.Design Heat LossHeat Pump\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Ambient Temperature<\/span><span class=\"mwh-entry-short\">The surrounding air temperature.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The surrounding air temperature. In heating, this often means the outside air temperature.<\/p><h3>In more detail<\/h3><p>Means the temperature of the air surrounding the item being discussed. Always check whether a specification means outdoor air, room air or a plant-room temperature; this changes how equipment performance should be interpreted.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A heat pump&#039;s output at a mild outdoor temperature may differ from its output on a freezing morning.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-design-heat-loss\" data-mwh-related=\"design-heat-loss\">Design Heat Loss<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-pump\" data-mwh-related=\"heat-pump\">Heat Pump<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ambient-temperature\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-asbestos-check\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"A\" data-categories=\"retrofit-standards\" data-search=\"Asbestos Check   A safety check to identify materials that may contain asbestos before retrofit works are carried out. A safety check to identify materials that may contain asbestos before retrofit works are carried out.In more detailThe type and extent of survey should suit the proposed work. Materials cannot reliably be cleared by appearance alone. Suspected asbestos should be assessed by a competent professional before drilling, cutting or removal; homeowners should not take samples themselves.A practical exampleInsulating a ceiling may require checks of materials that will be disturbed above it.Related termsThese are connected ideas, rather than always exact synonyms.AssessmentSpecificationFurther reading: HSE: asbestos surveys. Check current guidance for schemes and standards.\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Asbestos Check<\/span><span class=\"mwh-entry-short\">A safety check to identify materials that may contain asbestos before retrofit works are carried out.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A safety check to identify materials that may contain asbestos before retrofit works are carried out.<\/p><h3>In more detail<\/h3><p>The type and extent of survey should suit the proposed work. Materials cannot reliably be cleared by appearance alone. Suspected asbestos should be assessed by a competent professional before drilling, cutting or removal; homeowners should not take samples themselves.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Insulating a ceiling may require checks of materials that will be disturbed above it.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-assessment\" data-mwh-related=\"assessment\">Assessment<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-specification\" data-mwh-related=\"specification\">Specification<\/a><\/div><\/nav><p class=\"mwh-entry-source\">Further reading: <a href=\"https:\/\/www.hse.gov.uk\/asbestos\/duty\/arrange-asbestos-survey.htm\">HSE: asbestos surveys<\/a>. Check current guidance for schemes and standards.<\/p><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-asbestos-check\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-assessment\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"A\" data-categories=\"ventilation-air-quality\" data-search=\"Assessment   A detailed inspection of a property to understand its current condition, energy performance, heating systems, insulation, ventilation and retrofit suitability. A detailed inspection of a property to understand its current condition, energy performance, heating systems, insulation, ventilation and retrofit suitability.In more detailBrings evidence together rather than simply recommending products. Its scope should be clear: an EPC assessment, condition survey and retrofit assessment answer different questions. Ask what was inspected, what could not be inspected and what further investigation is needed.A practical exampleAn energy assessment can describe insulation without diagnosing the cause of a leaking roof.Related termsThese are connected ideas, rather than always exact synonyms.Retrofit AssessmentDomestic Energy Assessor\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Assessment<\/span><span class=\"mwh-entry-short\">A detailed inspection of a property to understand its current condition, energy performance, heating systems, insulation, ventilation and retrofit suitability.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A detailed inspection of a property to understand its current condition, energy performance, heating systems, insulation, ventilation and retrofit suitability.<\/p><h3>In more detail<\/h3><p>Brings evidence together rather than simply recommending products. Its scope should be clear: an EPC assessment, condition survey and retrofit assessment answer different questions. Ask what was inspected, what could not be inspected and what further investigation is needed.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An energy assessment can describe insulation without diagnosing the cause of a leaking roof.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-assessment\" data-mwh-related=\"retrofit-assessment\">Retrofit Assessment<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-domestic-energy-assessor\" data-mwh-related=\"domestic-energy-assessor\">Domestic Energy Assessor<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-assessment\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-assumed-pvgis-system-losses\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"A\" data-categories=\"\" data-search=\"Assumed PVGIS system losses (%) PVGIS  An allowance in a solar-output model for specified real-world system losses, such as wiring and inverter conversion losses. An allowance in a solar-output model for specified real-world system losses, such as wiring and inverter conversion losses.Also called: PVGISIn more detailPVGIS is a solar-output estimation tool. Its system-loss input allows for losses such as wiring, inverter conversion, dirt and mismatch. It is an assumption used in a model, not a guarantee or a replacement for checking shading and installation details.A practical exampleChanging the assumed losses changes the forecast annual electricity yield from the same panel array.Related termsThese are connected ideas, rather than always exact synonyms.Solar PVEnergy EfficiencyFurther reading: European Commission: PVGIS system losses. Check current guidance for schemes and standards.\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Assumed PVGIS system losses (%) <span class=\"mwh-entry-acronym\">PVGIS<\/span><\/span><span class=\"mwh-entry-short\">An allowance in a solar-output model for specified real-world system losses, such as wiring and inverter conversion losses.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">An allowance in a solar-output model for specified real-world system losses, such as wiring and inverter conversion losses.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> PVGIS<\/p><h3>In more detail<\/h3><p>PVGIS is a solar-output estimation tool. Its system-loss input allows for losses such as wiring, inverter conversion, dirt and mismatch. It is an assumption used in a model, not a guarantee or a replacement for checking shading and installation details.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Changing the assumed losses changes the forecast annual electricity yield from the same panel array.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solar-pv\" data-mwh-related=\"solar-pv\">Solar PV<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-energy-efficiency\" data-mwh-related=\"energy-efficiency\">Energy Efficiency<\/a><\/div><\/nav><p class=\"mwh-entry-source\">Further reading: <a href=\"https:\/\/joint-research-centre.ec.europa.eu\/photovoltaic-geographical-information-system-pvgis\/using-pvgis-5\/pvgis-5-tools\/grid-connected-pv_en\">European Commission: PVGIS system losses<\/a>. Check current guidance for schemes and standards.<\/p><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-assumed-pvgis-system-losses\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"B\" aria-labelledby=\"mwh-letter-B\"><h2 id=\"mwh-letter-B\" class=\"mwh-dictionary-letter\">B<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-background-ventilation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"B\" data-categories=\"ventilation-air-quality\" data-search=\"Background Ventilation   Low-level ventilation, usually through trickle vents or wall vents, that helps provide fresh air and manage moisture. Low-level ventilation, usually through trickle vents or wall vents, that helps provide fresh air and manage moisture.In more detailProvides a continuing route for outdoor air to enter occupied rooms. It is normally used with extraction from kitchens and bathrooms, and air-transfer paths between rooms. The required arrangement depends on the ventilation system.A practical exampleA bedroom trickle vent admits replacement air while a bathroom fan removes moist air elsewhere.Related termsThese are connected ideas, rather than always exact synonyms.Trickle VentWet Room Extract\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Background Ventilation<\/span><span class=\"mwh-entry-short\">Low-level ventilation, usually through trickle vents or wall vents, that helps provide fresh air and manage moisture.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Low-level ventilation, usually through trickle vents or wall vents, that helps provide fresh air and manage moisture.<\/p><h3>In more detail<\/h3><p>Provides a continuing route for outdoor air to enter occupied rooms. It is normally used with extraction from kitchens and bathrooms, and air-transfer paths between rooms. The required arrangement depends on the ventilation system.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A bedroom trickle vent admits replacement air while a bathroom fan removes moist air elsewhere.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-trickle-vent\" data-mwh-related=\"trickle-vent\">Trickle Vent<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-wet-room-extract\" data-mwh-related=\"wet-room-extract\">Wet Room Extract<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-background-ventilation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-balanced-flue\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"B\" data-categories=\"heating-hot-water\" data-search=\"Balanced Flue   A boiler flue system that takes air from outside for combustion and removes exhaust gases safely. A boiler flue system that takes air from outside for combustion and removes exhaust gases safely.In more detailOften uses concentric pipes, with combustion air entering around the exhaust route. It serves the appliance, not room ventilation. Terminal clearances and installation requirements must be checked by the appropriately qualified installer.A practical exampleA room-sealed boiler may have a balanced flue through an outside wall.Related termsThese are connected ideas, rather than always exact synonyms.FlueCombustion Ventilation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Balanced Flue<\/span><span class=\"mwh-entry-short\">A boiler flue system that takes air from outside for combustion and removes exhaust gases safely.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A boiler flue system that takes air from outside for combustion and removes exhaust gases safely.<\/p><h3>In more detail<\/h3><p>Often uses concentric pipes, with combustion air entering around the exhaust route. It serves the appliance, not room ventilation. Terminal clearances and installation requirements must be checked by the appropriately qualified installer.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A room-sealed boiler may have a balanced flue through an outside wall.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flue\" data-mwh-related=\"flue\">Flue<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-combustion-ventilation\" data-mwh-related=\"combustion-ventilation\">Combustion Ventilation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-balanced-flue\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-battery-storage\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"B\" data-categories=\"renewables-electricity\" data-search=\"Battery Storage   A system that stores electricity, often from solar panels, so it can be used later in the home. A system that stores electricity, often from solar panels, so it can be used later in the home.In more detailStores electricity after conversion and releases it when needed. Usable capacity in kWh, maximum charging\/discharging power in kW, efficiency and warranty are different specifications. A normal grid-connected battery does not automatically provide backup power during a power cut.A practical exampleSolar electricity stored at lunchtime may supply part of the evening demand.Related termsThese are connected ideas, rather than always exact synonyms.Solar PVKilowatt Hour\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Battery Storage<\/span><span class=\"mwh-entry-short\">A system that stores electricity, often from solar panels, so it can be used later in the home.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A system that stores electricity, often from solar panels, so it can be used later in the home.<\/p><h3>In more detail<\/h3><p>Stores electricity after conversion and releases it when needed. Usable capacity in kWh, maximum charging\/discharging power in kW, efficiency and warranty are different specifications. A normal grid-connected battery does not automatically provide backup power during a power cut.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Solar electricity stored at lunchtime may supply part of the evening demand.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solar-pv\" data-mwh-related=\"solar-pv\">Solar PV<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-kilowatt-hour\" data-mwh-related=\"kilowatt-hour\">Kilowatt Hour<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-battery-storage\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-biomass-boiler\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"B\" data-categories=\"heating-hot-water\" data-search=\"Biomass Boiler   A heating system that burns organic material, such as wood pellets or logs, to provide space heating and hot water. A heating system that burns organic material, such as wood pellets or logs, to provide space heating and hot water.In more detailBurns fuel such as logs, pellets or wood chips and needs suitable fuel storage, maintenance and a compliant flue. Renewable fuel does not mean zero local pollution or automatically low running costs; suitability depends on the property and supply chain.A practical exampleA pellet boiler needs space for fuel deliveries as well as the boiler itself.Related termsThese are connected ideas, rather than always exact synonyms.FlueLow Carbon Heating\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Biomass Boiler<\/span><span class=\"mwh-entry-short\">A heating system that burns organic material, such as wood pellets or logs, to provide space heating and hot water.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A heating system that burns organic material, such as wood pellets or logs, to provide space heating and hot water.<\/p><h3>In more detail<\/h3><p>Burns fuel such as logs, pellets or wood chips and needs suitable fuel storage, maintenance and a compliant flue. Renewable fuel does not mean zero local pollution or automatically low running costs; suitability depends on the property and supply chain.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A pellet boiler needs space for fuel deliveries as well as the boiler itself.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flue\" data-mwh-related=\"flue\">Flue<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-low-carbon-heating\" data-mwh-related=\"low-carbon-heating\">Low Carbon Heating<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-biomass-boiler\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-boiler\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"B\" data-categories=\"heating-hot-water\" data-search=\"Boiler   A heating appliance that heats water for radiators, underfloor heating or hot water cylinders. A heating appliance that heats water for radiators, underfloor heating or hot water cylinders. Common types include gas, oil, LPG and electric boilers.In more detailTransfers heat into water. Fuel-burning boilers and direct electric boilers obtain that heat differently, and their efficiency and emissions differ. Boiler output, heating demand and hot-water requirements should be assessed together rather than selecting a larger unit by default.A practical exampleA combi boiler may have a high output to heat tap water quickly, despite a much smaller space-heating demand.Related termsThese are connected ideas, rather than always exact synonyms.Combi BoilerSystem Boiler\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Boiler<\/span><span class=\"mwh-entry-short\">A heating appliance that heats water for radiators, underfloor heating or hot water cylinders.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A heating appliance that heats water for radiators, underfloor heating or hot water cylinders. Common types include gas, oil, LPG and electric boilers.<\/p><h3>In more detail<\/h3><p>Transfers heat into water. Fuel-burning boilers and direct electric boilers obtain that heat differently, and their efficiency and emissions differ. Boiler output, heating demand and hot-water requirements should be assessed together rather than selecting a larger unit by default.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A combi boiler may have a high output to heat tap water quickly, despite a much smaller space-heating demand.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-combi-boiler\" data-mwh-related=\"combi-boiler\">Combi Boiler<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-system-boiler\" data-mwh-related=\"system-boiler\">System Boiler<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-boiler\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-boiler-upgrade-scheme\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"B\" data-categories=\"heating-hot-water\" data-search=\"Boiler Upgrade Scheme BUS BUS A government grant scheme that can help with the cost of installing eligible low-carbon heating systems such as heat pumps. A government grant scheme that can help with the cost of installing eligible low-carbon heating systems such as heat pumps.Also called: BUSIn more detailSupports eligible low-carbon heating installations in England and Wales. Eligibility, technology rules and grant amounts can change, so check the current official scheme guidance before relying on a quotation. An application or advertised grant does not guarantee that every project qualifies.A practical exampleAn installer checks the property and proposed heat-pump installation against the scheme rules before an application.Related termsThese are connected ideas, rather than always exact synonyms.Heat PumpMicrogeneration Certification SchemeFurther reading: Government: Boiler Upgrade Scheme. Check current guidance for schemes and standards.\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Boiler Upgrade Scheme <span class=\"mwh-entry-acronym\">BUS<\/span><\/span><span class=\"mwh-entry-short\">A government grant scheme that can help with the cost of installing eligible low-carbon heating systems such as heat pumps.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A government grant scheme that can help with the cost of installing eligible low-carbon heating systems such as heat pumps.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> BUS<\/p><h3>In more detail<\/h3><p>Supports eligible low-carbon heating installations in England and Wales. Eligibility, technology rules and grant amounts can change, so check the current official scheme guidance before relying on a quotation. An application or advertised grant does not guarantee that every project qualifies.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An installer checks the property and proposed heat-pump installation against the scheme rules before an application.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-pump\" data-mwh-related=\"heat-pump\">Heat Pump<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-microgeneration-certification-scheme\" data-mwh-related=\"microgeneration-certification-scheme\">Microgeneration Certification Scheme<\/a><\/div><\/nav><p class=\"mwh-entry-source\">Further reading: <a href=\"https:\/\/www.gov.uk\/apply-boiler-upgrade-scheme\">Government: Boiler Upgrade Scheme<\/a>. Check current guidance for schemes and standards.<\/p><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-boiler-upgrade-scheme\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-breathability\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"B\" data-categories=\"moisture-damp\" data-search=\"Breathability   An informal term describing how a material or construction manages moisture; it is not the same as allowing air to leak through. An informal term describing how a material or construction manages moisture; it is not the same as allowing air to leak through.In more detailAn informal description of moisture movement, not a single product rating. Vapour diffusion, liquid-water transport and drying ability are different properties. A wall&#039;s finishes and complete build-up matter as much as one material labelled breathable.A practical exampleA vapour-open plaster cannot compensate for an unsuitable impermeable layer elsewhere in the wall.Related termsThese are connected ideas, rather than always exact synonyms.Vapour Control LayerLime Plaster\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Breathability<\/span><span class=\"mwh-entry-short\">An informal term describing how a material or construction manages moisture; it is not the same as allowing air to leak through.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">An informal term describing how a material or construction manages moisture; it is not the same as allowing air to leak through.<\/p><h3>In more detail<\/h3><p>An informal description of moisture movement, not a single product rating. Vapour diffusion, liquid-water transport and drying ability are different properties. A wall&#039;s finishes and complete build-up matter as much as one material labelled breathable.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A vapour-open plaster cannot compensate for an unsuitable impermeable layer elsewhere in the wall.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-vapour-control-layer\" data-mwh-related=\"vapour-control-layer\">Vapour Control Layer<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-lime-plaster\" data-mwh-related=\"lime-plaster\">Lime Plaster<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-breathability\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-breather-membrane\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"B\" data-categories=\"moisture-damp\" data-search=\"Breather Membrane   A membrane used in walls or roofs that helps protect against water while allowing water vapour to escape. A membrane used in walls or roofs that helps protect against water while allowing water vapour to escape.In more detailResists wind-driven rain while allowing a specified degree of water-vapour passage. It is not interchangeable with a vapour-control layer. Laps, penetrations, support and ventilation spaces must follow the complete roof or wall design.A practical exampleA membrane below roof tiles may protect the construction while allowing some drying outwards.Related termsThese are connected ideas, rather than always exact synonyms.Vapour Control LayerWarm Roof\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Breather Membrane<\/span><span class=\"mwh-entry-short\">A membrane used in walls or roofs that helps protect against water while allowing water vapour to escape.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A membrane used in walls or roofs that helps protect against water while allowing water vapour to escape.<\/p><h3>In more detail<\/h3><p>Resists wind-driven rain while allowing a specified degree of water-vapour passage. It is not interchangeable with a vapour-control layer. Laps, penetrations, support and ventilation spaces must follow the complete roof or wall design.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A membrane below roof tiles may protect the construction while allowing some drying outwards.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-vapour-control-layer\" data-mwh-related=\"vapour-control-layer\">Vapour Control Layer<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-warm-roof\" data-mwh-related=\"warm-roof\">Warm Roof<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-breather-membrane\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-bridging\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"B\" data-categories=\"moisture-damp\" data-search=\"Bridging   A route that bypasses a protective layer, such as insulation or a damp-proof barrier. Its meaning depends on the context. A route that bypasses a protective layer, such as insulation or a damp-proof barrier. Its meaning depends on the context.In more detailHas different meanings in different contexts. A thermal bridge provides an easier route for heat flow; a damp-proof-course bridge allows moisture to bypass a barrier. The report should say which is meant and identify the actual detail.A practical exampleRaised garden soil above a damp-proof course is moisture bridging, not the same thing as a concrete lintel&#039;s thermal bridge.Related termsThese are connected ideas, rather than always exact synonyms.Thermal BridgeDamp Proof Course\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Bridging<\/span><span class=\"mwh-entry-short\">A route that bypasses a protective layer, such as insulation or a damp-proof barrier. Its meaning depends on the context.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A route that bypasses a protective layer, such as insulation or a damp-proof barrier. Its meaning depends on the context.<\/p><h3>In more detail<\/h3><p>Has different meanings in different contexts. A thermal bridge provides an easier route for heat flow; a damp-proof-course bridge allows moisture to bypass a barrier. The report should say which is meant and identify the actual detail.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Raised garden soil above a damp-proof course is moisture bridging, not the same thing as a concrete lintel&#039;s thermal bridge.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-bridge\" data-mwh-related=\"thermal-bridge\">Thermal Bridge<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-damp-proof-course\" data-mwh-related=\"damp-proof-course\">Damp Proof Course<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-bridging\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-building-fabric\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"B\" data-categories=\"building-fabric-insulation\" data-search=\"Building Fabric   The physical parts of a building that separate the inside from the outside, including walls, floors, roofs, windows and doors. The physical parts of a building that separate the inside from the outside, including walls, floors, roofs, windows and doors.In more detailIncludes the construction and its junctions rather than the heating equipment. Insulation, weather resistance, airtightness and moisture behaviour all depend on how these parts work together. A good fabric assessment also looks for defects before covering them.A practical exampleA roof&#039;s insulation, underlay, tiles and loft hatch each affect its overall performance.Related termsThese are connected ideas, rather than always exact synonyms.Thermal EnvelopeFabric First\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Building Fabric<\/span><span class=\"mwh-entry-short\">The physical parts of a building that separate the inside from the outside, including walls, floors, roofs, windows and doors.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The physical parts of a building that separate the inside from the outside, including walls, floors, roofs, windows and doors.<\/p><h3>In more detail<\/h3><p>Includes the construction and its junctions rather than the heating equipment. Insulation, weather resistance, airtightness and moisture behaviour all depend on how these parts work together. A good fabric assessment also looks for defects before covering them.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A roof&#039;s insulation, underlay, tiles and loft hatch each affect its overall performance.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-envelope\" data-mwh-related=\"thermal-envelope\">Thermal Envelope<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-fabric-first\" data-mwh-related=\"fabric-first\">Fabric First<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-building-fabric\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"C\" aria-labelledby=\"mwh-letter-C\"><h2 id=\"mwh-letter-C\" class=\"mwh-dictionary-letter\">C<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-cavity-wall\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"building-fabric-insulation\" data-search=\"Cavity Wall   A wall with two leaves, usually brick or blockwork, separated by a gap or cavity. A wall with two leaves, usually brick or blockwork, separated by a gap or cavity.In more detailUsually has an outer weather-facing leaf and an inner structural leaf separated by a gap. The cavity may be empty, partly insulated or filled. Suitability for extra insulation depends on construction, condition and exposure, not just the existence of a gap.A practical exampleA survey may find mortar debris or rain exposure that needs consideration before filling the cavity.Related termsThese are connected ideas, rather than always exact synonyms.Cavity Wall InsulationCavity Wall Extraction\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Cavity Wall<\/span><span class=\"mwh-entry-short\">A wall with two leaves, usually brick or blockwork, separated by a gap or cavity.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A wall with two leaves, usually brick or blockwork, separated by a gap or cavity.<\/p><h3>In more detail<\/h3><p>Usually has an outer weather-facing leaf and an inner structural leaf separated by a gap. The cavity may be empty, partly insulated or filled. Suitability for extra insulation depends on construction, condition and exposure, not just the existence of a gap.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A survey may find mortar debris or rain exposure that needs consideration before filling the cavity.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-cavity-wall-insulation\" data-mwh-related=\"cavity-wall-insulation\">Cavity Wall Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-cavity-wall-extraction\" data-mwh-related=\"cavity-wall-extraction\">Cavity Wall Extraction<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-cavity-wall\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-cavity-wall-extraction\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"building-fabric-insulation\" data-search=\"Cavity Wall Extraction   The removal of failed, unsuitable or wet cavity wall insulation from a property. The removal of failed, unsuitable or wet cavity wall insulation from a property.In more detailA remedial process that should follow an investigation showing why removal is needed. Extraction alone may not repair defective gutters, pointing or other sources of water. The removal method and post-work checks should suit the insulation and wall.A practical exampleWet insulation may be removed while a separate defect allowing rainwater in is repaired.Related termsThese are connected ideas, rather than always exact synonyms.Cavity Wall InsulationPenetrating Damp\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Cavity Wall Extraction<\/span><span class=\"mwh-entry-short\">The removal of failed, unsuitable or wet cavity wall insulation from a property.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The removal of failed, unsuitable or wet cavity wall insulation from a property.<\/p><h3>In more detail<\/h3><p>A remedial process that should follow an investigation showing why removal is needed. Extraction alone may not repair defective gutters, pointing or other sources of water. The removal method and post-work checks should suit the insulation and wall.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Wet insulation may be removed while a separate defect allowing rainwater in is repaired.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-cavity-wall-insulation\" data-mwh-related=\"cavity-wall-insulation\">Cavity Wall Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-penetrating-damp\" data-mwh-related=\"penetrating-damp\">Penetrating Damp<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-cavity-wall-extraction\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-cavity-wall-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"building-fabric-insulation\" data-search=\"Cavity Wall Insulation CWI CWI Insulation installed into the cavity between the inner and outer leaves of a wall to reduce heat loss. Insulation installed into the cavity between the inner and outer leaves of a wall to reduce heat loss.Also called: CWIIn more detailReduces heat transfer across an appropriate cavity. The insulation type and installation method must match the wall, cavity width and exposure. Surveying for defects and checking installation quality are essential; not every cavity should be filled.A practical exampleA suitable dry, clean cavity may be filled with an approved bead or fibre system.Related termsThese are connected ideas, rather than always exact synonyms.Cavity WallQuality Assurance\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Cavity Wall Insulation <span class=\"mwh-entry-acronym\">CWI<\/span><\/span><span class=\"mwh-entry-short\">Insulation installed into the cavity between the inner and outer leaves of a wall to reduce heat loss.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Insulation installed into the cavity between the inner and outer leaves of a wall to reduce heat loss.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> CWI<\/p><h3>In more detail<\/h3><p>Reduces heat transfer across an appropriate cavity. The insulation type and installation method must match the wall, cavity width and exposure. Surveying for defects and checking installation quality are essential; not every cavity should be filled.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A suitable dry, clean cavity may be filled with an approved bead or fibre system.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-cavity-wall\" data-mwh-related=\"cavity-wall\">Cavity Wall<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-quality-assurance\" data-mwh-related=\"quality-assurance\">Quality Assurance<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-cavity-wall-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-cellulose-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"building-fabric-insulation\" data-search=\"Cellulose Insulation   Insulation made from recycled paper fibres. Insulation made from recycled paper fibres. It is often used in lofts, timber frames and some breathable construction systems.In more detailUsually consists of treated recycled paper fibres, installed loose, blown or densely packed depending on the application. Density, settlement, moisture control and fire performance must be considered as part of the specified system.A practical exampleA roof void may use blown cellulose at a designed thickness and density.Related termsThese are connected ideas, rather than always exact synonyms.InsulationLoft Insulation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Cellulose Insulation<\/span><span class=\"mwh-entry-short\">Insulation made from recycled paper fibres.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Insulation made from recycled paper fibres. It is often used in lofts, timber frames and some breathable construction systems.<\/p><h3>In more detail<\/h3><p>Usually consists of treated recycled paper fibres, installed loose, blown or densely packed depending on the application. Density, settlement, moisture control and fire performance must be considered as part of the specified system.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A roof void may use blown cellulose at a designed thickness and density.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-insulation\" data-mwh-related=\"insulation\">Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-loft-insulation\" data-mwh-related=\"loft-insulation\">Loft Insulation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-cellulose-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-central-heating\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"heating-hot-water\" data-search=\"Central Heating   A heating system where heat is generated in one place, such as a boiler or heat pump, and distributed around the home. A heating system where heat is generated in one place, such as a boiler or heat pump, and distributed around the home.In more detailDescribes heat distributed from a common source to several rooms. A wet system circulates heated water through pipes; controls and hydraulic balancing influence comfort. The heat source may change without every radiator or pipe necessarily needing replacement.A practical exampleA heat pump can supply a suitably designed wet central-heating system.Related termsThese are connected ideas, rather than always exact synonyms.EmitterHeating Controls\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Central Heating<\/span><span class=\"mwh-entry-short\">A heating system where heat is generated in one place, such as a boiler or heat pump, and distributed around the home.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A heating system where heat is generated in one place, such as a boiler or heat pump, and distributed around the home.<\/p><h3>In more detail<\/h3><p>Describes heat distributed from a common source to several rooms. A wet system circulates heated water through pipes; controls and hydraulic balancing influence comfort. The heat source may change without every radiator or pipe necessarily needing replacement.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A heat pump can supply a suitably designed wet central-heating system.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-emitter\" data-mwh-related=\"emitter\">Emitter<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heating-controls\" data-mwh-related=\"heating-controls\">Heating Controls<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-central-heating\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-coefficient-of-performance\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"heating-hot-water\" data-search=\"Coefficient of Performance CoP CoP A measure of heat pump efficiency at a particular moment. A measure of heat pump efficiency at a particular moment. A CoP of 3 means the heat pump is producing three units of heat for every one unit of electricity used.Also called: CoPIn more detailCompares useful heat output with electrical input at stated operating conditions. It is a ratio, not a fixed promise for the whole year. Outdoor temperature, water temperature and what equipment is included in the measurement affect the result.A practical exampleA CoP of 3 means 3 kWh of heat for 1 kWh of electricity under those conditions.Related termsThese are connected ideas, rather than always exact synonyms.Seasonal Coefficient of PerformanceSeasonal Performance Factor\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Coefficient of Performance <span class=\"mwh-entry-acronym\">CoP<\/span><\/span><span class=\"mwh-entry-short\">A measure of heat pump efficiency at a particular moment.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A measure of heat pump efficiency at a particular moment. A CoP of 3 means the heat pump is producing three units of heat for every one unit of electricity used.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> CoP<\/p><h3>In more detail<\/h3><p>Compares useful heat output with electrical input at stated operating conditions. It is a ratio, not a fixed promise for the whole year. Outdoor temperature, water temperature and what equipment is included in the measurement affect the result.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A CoP of 3 means 3 kWh of heat for 1 kWh of electricity under those conditions.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-seasonal-coefficient-of-performance\" data-mwh-related=\"seasonal-coefficient-of-performance\">Seasonal Coefficient of Performance<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-seasonal-performance-factor\" data-mwh-related=\"seasonal-performance-factor\">Seasonal Performance Factor<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-coefficient-of-performance\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-cold-bridge\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"moisture-damp\" data-search=\"Cold Bridge   Another term for a thermal bridge. Another term for a thermal bridge. It is an area where heat escapes more easily, often causing cold spots or condensation risk.In more detailA common alternative name for a thermal bridge. The area can feel colder inside because heat flows through it more readily. That lower surface temperature may increase condensation risk, even when no water is entering from outside.A practical exampleThe inside corner beside an uninsulated concrete lintel can become a cold spot.Related termsThese are connected ideas, rather than always exact synonyms.Thermal BridgeCondensation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Cold Bridge<\/span><span class=\"mwh-entry-short\">Another term for a thermal bridge.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Another term for a thermal bridge. It is an area where heat escapes more easily, often causing cold spots or condensation risk.<\/p><h3>In more detail<\/h3><p>A common alternative name for a thermal bridge. The area can feel colder inside because heat flows through it more readily. That lower surface temperature may increase condensation risk, even when no water is entering from outside.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>The inside corner beside an uninsulated concrete lintel can become a cold spot.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-bridge\" data-mwh-related=\"thermal-bridge\">Thermal Bridge<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-condensation\" data-mwh-related=\"condensation\">Condensation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-cold-bridge\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-combi-boiler\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"heating-hot-water\" data-search=\"Combi Boiler   A boiler that provides heating and hot water directly, without needing a separate hot water cylinder. A boiler that provides heating and hot water directly, without needing a separate hot water cylinder.In more detailHeats incoming mains water when a hot tap runs, rather than storing it in a separate cylinder. Hot-water flow depends on appliance output and incoming water conditions. Space-heating and hot-water performance are separate design considerations.A practical exampleOpening two showers at once may reduce the hot-water flow available to each.Related termsThese are connected ideas, rather than always exact synonyms.BoilerDomestic Hot Water\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Combi Boiler<\/span><span class=\"mwh-entry-short\">A boiler that provides heating and hot water directly, without needing a separate hot water cylinder.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A boiler that provides heating and hot water directly, without needing a separate hot water cylinder.<\/p><h3>In more detail<\/h3><p>Heats incoming mains water when a hot tap runs, rather than storing it in a separate cylinder. Hot-water flow depends on appliance output and incoming water conditions. Space-heating and hot-water performance are separate design considerations.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Opening two showers at once may reduce the hot-water flow available to each.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-boiler\" data-mwh-related=\"boiler\">Boiler<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-domestic-hot-water\" data-mwh-related=\"domestic-hot-water\">Domestic Hot Water<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-combi-boiler\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-combustion-ventilation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"ventilation-air-quality\" data-search=\"Combustion Ventilation   Ventilation required for appliances that burn fuel, such as gas, oil, LPG, coal or wood. Ventilation required for appliances that burn fuel, such as gas, oil, LPG, coal or wood.In more detailSupplies air needed for safe fuel burning where the appliance design requires it. It must not be removed during draught-proofing or insulation work. Requirements depend on the appliance, flue and installation; a competent specialist should assess changes.A practical exampleA required permanent air vent serving a stove must not be taped over to stop a draught.Related termsThese are connected ideas, rather than always exact synonyms.FlueDraught Proofing\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Combustion Ventilation<\/span><span class=\"mwh-entry-short\">Ventilation required for appliances that burn fuel, such as gas, oil, LPG, coal or wood.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Ventilation required for appliances that burn fuel, such as gas, oil, LPG, coal or wood.<\/p><h3>In more detail<\/h3><p>Supplies air needed for safe fuel burning where the appliance design requires it. It must not be removed during draught-proofing or insulation work. Requirements depend on the appliance, flue and installation; a competent specialist should assess changes.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A required permanent air vent serving a stove must not be taped over to stop a draught.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flue\" data-mwh-related=\"flue\">Flue<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-draught-proofing\" data-mwh-related=\"draught-proofing\">Draught Proofing<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-combustion-ventilation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-commissioning\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"retrofit-standards\" data-search=\"Commissioning   The process of checking, setting up and recording that a system has been installed correctly and is working as designed. The process of checking, setting up and recording that a system has been installed correctly and is working as designed.In more detailConfirms that installed equipment performs as intended, with settings and measurements recorded. Turning it on is only one part of the process. Handover should include operating instructions, maintenance needs and evidence of the checks completed.A practical exampleA ventilation installer measures airflow at each extract point instead of merely checking that the fan spins.Related termsThese are connected ideas, rather than always exact synonyms.Quality AssuranceVentilation Rate\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Commissioning<\/span><span class=\"mwh-entry-short\">The process of checking, setting up and recording that a system has been installed correctly and is working as designed.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The process of checking, setting up and recording that a system has been installed correctly and is working as designed.<\/p><h3>In more detail<\/h3><p>Confirms that installed equipment performs as intended, with settings and measurements recorded. Turning it on is only one part of the process. Handover should include operating instructions, maintenance needs and evidence of the checks completed.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A ventilation installer measures airflow at each extract point instead of merely checking that the fan spins.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-quality-assurance\" data-mwh-related=\"quality-assurance\">Quality Assurance<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ventilation-rate\" data-mwh-related=\"ventilation-rate\">Ventilation Rate<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-commissioning\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-compensation-controls\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"controls\" data-search=\"Compensation Controls   Heating controls that adjust flow temperature depending on internal or external conditions. Heating controls that adjust flow temperature depending on internal or external conditions.In more detailAdjust the heating water temperature as conditions change, rather than always running at one high setting. Weather compensation uses outdoor conditions; load compensation responds to indoor demand. The controller and heat source must be compatible and set up correctly.A practical exampleOn a mild day, a compensated system may send cooler water to radiators for longer periods.Related termsThese are connected ideas, rather than always exact synonyms.Weather CompensationHeating Curve\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Compensation Controls<\/span><span class=\"mwh-entry-short\">Heating controls that adjust flow temperature depending on internal or external conditions.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Heating controls that adjust flow temperature depending on internal or external conditions.<\/p><h3>In more detail<\/h3><p>Adjust the heating water temperature as conditions change, rather than always running at one high setting. Weather compensation uses outdoor conditions; load compensation responds to indoor demand. The controller and heat source must be compatible and set up correctly.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>On a mild day, a compensated system may send cooler water to radiators for longer periods.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-weather-compensation\" data-mwh-related=\"weather-compensation\">Weather Compensation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heating-curve\" data-mwh-related=\"heating-curve\">Heating Curve<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-compensation-controls\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-condensation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"ventilation-air-quality\" data-search=\"Condensation   Water droplets that form when warm moist air meets a cold surface. Water droplets that form when warm moist air meets a cold surface. It is common on windows, cold walls and areas with poor ventilation.In more detailForms when a surface is cold enough for water vapour in nearby air to turn to liquid. The surface temperature and amount of moisture both matter. Persistent problems require checking moisture sources, ventilation, heating and cold surfaces together.A practical exampleWater on the inside of a bedroom window on a cold morning is a familiar example.Related termsThese are connected ideas, rather than always exact synonyms.Dew PointRelative Humidity\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Condensation<\/span><span class=\"mwh-entry-short\">Water droplets that form when warm moist air meets a cold surface.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Water droplets that form when warm moist air meets a cold surface. It is common on windows, cold walls and areas with poor ventilation.<\/p><h3>In more detail<\/h3><p>Forms when a surface is cold enough for water vapour in nearby air to turn to liquid. The surface temperature and amount of moisture both matter. Persistent problems require checking moisture sources, ventilation, heating and cold surfaces together.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Water on the inside of a bedroom window on a cold morning is a familiar example.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-dew-point\" data-mwh-related=\"dew-point\">Dew Point<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-relative-humidity\" data-mwh-related=\"relative-humidity\">Relative Humidity<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-condensation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-condenser\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"heating-hot-water\" data-search=\"Condenser   In a heat pump or refrigeration cycle, the condenser is the heat exchanger where the refrigerant releases heat into the heating system. In a heat pump or refrigeration cycle, the condenser is the heat exchanger where the refrigerant releases heat into the heating system.In more detailThe part of a heat pump&#039;s refrigerant circuit where heat is released as refrigerant condenses. In an air-to-water heating system, that heat is normally transferred into circulating water. It should not be confused with a condensing boiler.A practical exampleA heat exchanger transfers heat from refrigerant to the radiator-water circuit without mixing the fluids.Related termsThese are connected ideas, rather than always exact synonyms.Refrigeration CycleHeat Exchanger\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Condenser<\/span><span class=\"mwh-entry-short\">In a heat pump or refrigeration cycle, the condenser is the heat exchanger where the refrigerant releases heat into the heating system.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">In a heat pump or refrigeration cycle, the condenser is the heat exchanger where the refrigerant releases heat into the heating system.<\/p><h3>In more detail<\/h3><p>The part of a heat pump&#039;s refrigerant circuit where heat is released as refrigerant condenses. In an air-to-water heating system, that heat is normally transferred into circulating water. It should not be confused with a condensing boiler.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A heat exchanger transfers heat from refrigerant to the radiator-water circuit without mixing the fluids.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-refrigeration-cycle\" data-mwh-related=\"refrigeration-cycle\">Refrigeration Cycle<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-exchanger\" data-mwh-related=\"heat-exchanger\">Heat Exchanger<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-condenser\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-conservation-area\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"retrofit-standards\" data-search=\"Conservation Area   An area with special architectural or historic interest. An area with special architectural or historic interest. Some retrofit measures may need extra care or permissions.In more detailProtects the character of an area rather than only individual buildings. Some external changes may be controlled, and local restrictions vary. Check the relevant planning authority before assuming that a measure is permitted without an application.A practical exampleWindow replacement or external insulation may need a different approach from the same work outside the area.Related termsThese are connected ideas, rather than always exact synonyms.Planning PermissionListed Building\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Conservation Area<\/span><span class=\"mwh-entry-short\">An area with special architectural or historic interest.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">An area with special architectural or historic interest. Some retrofit measures may need extra care or permissions.<\/p><h3>In more detail<\/h3><p>Protects the character of an area rather than only individual buildings. Some external changes may be controlled, and local restrictions vary. Check the relevant planning authority before assuming that a measure is permitted without an application.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Window replacement or external insulation may need a different approach from the same work outside the area.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-planning-permission\" data-mwh-related=\"planning-permission\">Planning Permission<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-listed-building\" data-mwh-related=\"listed-building\">Listed Building<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-conservation-area\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-controls\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"C\" data-categories=\"controls\" data-search=\"Controls   The timers, thermostats, programmers, smart controls and sensors that manage heating, hot water and ventilation systems. The timers, thermostats, programmers, smart controls and sensors that manage heating, hot water and ventilation systems.In more detailManage when systems run and the conditions they maintain. Good controls need sensible positioning, suitable settings and clear instructions. More features do not automatically mean lower bills; compatibility and how the household uses them matter.A practical exampleA programmer sets heating times while a thermostat responds to the actual room temperature.Related termsThese are connected ideas, rather than always exact synonyms.ThermostatHeating Controls\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Controls<\/span><span class=\"mwh-entry-short\">The timers, thermostats, programmers, smart controls and sensors that manage heating, hot water and ventilation systems.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The timers, thermostats, programmers, smart controls and sensors that manage heating, hot water and ventilation systems.<\/p><h3>In more detail<\/h3><p>Manage when systems run and the conditions they maintain. Good controls need sensible positioning, suitable settings and clear instructions. More features do not automatically mean lower bills; compatibility and how the household uses them matter.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A programmer sets heating times while a thermostat responds to the actual room temperature.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermostat\" data-mwh-related=\"thermostat\">Thermostat<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heating-controls\" data-mwh-related=\"heating-controls\">Heating Controls<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-controls\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"D\" aria-labelledby=\"mwh-letter-D\"><h2 id=\"mwh-letter-D\" class=\"mwh-dictionary-letter\">D<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-damp\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"D\" data-categories=\"moisture-damp\" data-search=\"Damp   Unwanted moisture in a building. Unwanted moisture in a building. Common types include penetrating damp, rising damp, condensation-related damp and trapped moisture.In more detailA description of excess moisture, not a diagnosis. Water may come from rain, plumbing, ground moisture or condensation, and several causes can overlap. The pattern, timing, construction and measurements should be assessed before selecting treatment.A practical exampleA low wall stain could be caused by a leaking pipe rather than rising damp.Related termsThese are connected ideas, rather than always exact synonyms.Penetrating DampRising Damp\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Damp<\/span><span class=\"mwh-entry-short\">Unwanted moisture in a building.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Unwanted moisture in a building. Common types include penetrating damp, rising damp, condensation-related damp and trapped moisture.<\/p><h3>In more detail<\/h3><p>A description of excess moisture, not a diagnosis. Water may come from rain, plumbing, ground moisture or condensation, and several causes can overlap. The pattern, timing, construction and measurements should be assessed before selecting treatment.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A low wall stain could be caused by a leaking pipe rather than rising damp.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-penetrating-damp\" data-mwh-related=\"penetrating-damp\">Penetrating Damp<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-rising-damp\" data-mwh-related=\"rising-damp\">Rising Damp<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-damp\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-damp-proof-course\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"D\" data-categories=\"moisture-damp\" data-search=\"Damp Proof Course DPC DPC A physical or chemical barrier designed to stop moisture rising through walls. A physical or chemical barrier designed to stop moisture rising through walls.Also called: DPCIn more detailA layer intended to limit moisture moving upwards through a wall. It may be a physical material or a suitable remedial treatment. Raised soil, debris or other details can bypass it; a low damp patch alone does not demonstrate failure.A practical examplePaving installed too high can bridge an otherwise intact damp-proof course.Related termsThese are connected ideas, rather than always exact synonyms.BridgingRising Damp\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Damp Proof Course <span class=\"mwh-entry-acronym\">DPC<\/span><\/span><span class=\"mwh-entry-short\">A physical or chemical barrier designed to stop moisture rising through walls.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A physical or chemical barrier designed to stop moisture rising through walls.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> DPC<\/p><h3>In more detail<\/h3><p>A layer intended to limit moisture moving upwards through a wall. It may be a physical material or a suitable remedial treatment. Raised soil, debris or other details can bypass it; a low damp patch alone does not demonstrate failure.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Paving installed too high can bridge an otherwise intact damp-proof course.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-bridging\" data-mwh-related=\"bridging\">Bridging<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-rising-damp\" data-mwh-related=\"rising-damp\">Rising Damp<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-damp-proof-course\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-decarbonisation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"D\" data-categories=\"renewables-electricity\" data-search=\"Decarbonisation   The process of reducing carbon emissions, often by improving insulation, reducing energy demand and switching to low-carbon heating. The process of reducing carbon emissions, often by improving insulation, reducing energy demand and switching to low-carbon heating.In more detailMeans reducing greenhouse-gas emissions associated with an activity. In housing, changes to energy demand, heat sources and electricity supply all affect the result. Operational emissions and emissions from making building materials are different parts of the overall picture.A practical exampleInsulating a home and replacing fossil-fuel heating can both contribute, through different mechanisms.Related termsThese are connected ideas, rather than always exact synonyms.Low Carbon HeatingEnergy Efficiency\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Decarbonisation<\/span><span class=\"mwh-entry-short\">The process of reducing carbon emissions, often by improving insulation, reducing energy demand and switching to low-carbon heating.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The process of reducing carbon emissions, often by improving insulation, reducing energy demand and switching to low-carbon heating.<\/p><h3>In more detail<\/h3><p>Means reducing greenhouse-gas emissions associated with an activity. In housing, changes to energy demand, heat sources and electricity supply all affect the result. Operational emissions and emissions from making building materials are different parts of the overall picture.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Insulating a home and replacing fossil-fuel heating can both contribute, through different mechanisms.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-low-carbon-heating\" data-mwh-related=\"low-carbon-heating\">Low Carbon Heating<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-energy-efficiency\" data-mwh-related=\"energy-efficiency\">Energy Efficiency<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-decarbonisation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-design-flow-temperature\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"D\" data-categories=\"heating-hot-water\" data-search=\"Design Flow Temperature   The water temperature a heating system is designed to send to radiators or underfloor heating. The water temperature a heating system is designed to send to radiators or underfloor heating. Lower flow temperatures are usually better for heat pump efficiency.In more detailThe chosen supply-water temperature at the system&#039;s design conditions, usually a cold outdoor temperature. It must work with room heat losses, emitter sizes and water flow. It is not necessarily the temperature used on every day of the year.A practical exampleA system designed for lower flow temperatures may require larger radiators in some rooms.Related termsThese are connected ideas, rather than always exact synonyms.Emitter SizingWeather Compensation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Design Flow Temperature<\/span><span class=\"mwh-entry-short\">The water temperature a heating system is designed to send to radiators or underfloor heating.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The water temperature a heating system is designed to send to radiators or underfloor heating. Lower flow temperatures are usually better for heat pump efficiency.<\/p><h3>In more detail<\/h3><p>The chosen supply-water temperature at the system&#039;s design conditions, usually a cold outdoor temperature. It must work with room heat losses, emitter sizes and water flow. It is not necessarily the temperature used on every day of the year.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A system designed for lower flow temperatures may require larger radiators in some rooms.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-emitter-sizing\" data-mwh-related=\"emitter-sizing\">Emitter Sizing<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-weather-compensation\" data-mwh-related=\"weather-compensation\">Weather Compensation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-design-flow-temperature\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-design-heat-loss\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"D\" data-categories=\"heating-hot-water\" data-search=\"Design Heat Loss   The amount of heat a property or room is expected to lose during cold weather. The amount of heat a property or room is expected to lose during cold weather. It is used to size heating systems correctly.In more detailEstimates the heat needed to maintain chosen indoor temperatures at specified cold outdoor conditions. It helps select equipment capacity. It is a power figure, normally in kW, rather than an annual energy-use estimate.A practical exampleA room losing 800 watts at the design condition needs an emitter capable of covering that load.Related termsThese are connected ideas, rather than always exact synonyms.Heat Loss CalculationPeak Load\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Design Heat Loss<\/span><span class=\"mwh-entry-short\">The amount of heat a property or room is expected to lose during cold weather.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The amount of heat a property or room is expected to lose during cold weather. It is used to size heating systems correctly.<\/p><h3>In more detail<\/h3><p>Estimates the heat needed to maintain chosen indoor temperatures at specified cold outdoor conditions. It helps select equipment capacity. It is a power figure, normally in kW, rather than an annual energy-use estimate.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A room losing 800 watts at the design condition needs an emitter capable of covering that load.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-loss-calculation\" data-mwh-related=\"heat-loss-calculation\">Heat Loss Calculation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-peak-load\" data-mwh-related=\"peak-load\">Peak Load<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-design-heat-loss\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-dew-point\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"D\" data-categories=\"moisture-damp\" data-search=\"Dew Point   The temperature at which water vapour turns into liquid water. The temperature at which water vapour turns into liquid water. It is important when assessing condensation risk.In more detailThe temperature at which air with a given moisture content becomes saturated. A surface below that temperature can collect condensation. Changing the room humidity changes the dew point, so there is no single dew-point temperature for every home.A practical exampleA cold window can be below dew point even while the room air feels comfortably warm.Related termsThese are connected ideas, rather than always exact synonyms.Relative HumidityCondensation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Dew Point<\/span><span class=\"mwh-entry-short\">The temperature at which water vapour turns into liquid water.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The temperature at which water vapour turns into liquid water. It is important when assessing condensation risk.<\/p><h3>In more detail<\/h3><p>The temperature at which air with a given moisture content becomes saturated. A surface below that temperature can collect condensation. Changing the room humidity changes the dew point, so there is no single dew-point temperature for every home.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A cold window can be below dew point even while the room air feels comfortably warm.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-relative-humidity\" data-mwh-related=\"relative-humidity\">Relative Humidity<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-condensation\" data-mwh-related=\"condensation\">Condensation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-dew-point\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-direct-electric-heating\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"D\" data-categories=\"heating-hot-water\" data-search=\"Direct Electric Heating   Heating that uses electricity directly, such as panel heaters, storage heaters, electric radiators or infrared panels. Heating that uses electricity directly, such as panel heaters, storage heaters, electric radiators or infrared panels.In more detailTurns electricity into heat at the point of use, rather than moving heat from outdoors as a heat pump does. Purchase price, tariff, controls and heat demand influence running costs. Efficient conversion alone does not guarantee cheap heating.A practical exampleA 1 kW panel heater operating continuously for one hour uses about 1 kWh of electricity.Related termsThese are connected ideas, rather than always exact synonyms.Heat PumpKilowatt Hour\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Direct Electric Heating<\/span><span class=\"mwh-entry-short\">Heating that uses electricity directly, such as panel heaters, storage heaters, electric radiators or infrared panels.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Heating that uses electricity directly, such as panel heaters, storage heaters, electric radiators or infrared panels.<\/p><h3>In more detail<\/h3><p>Turns electricity into heat at the point of use, rather than moving heat from outdoors as a heat pump does. Purchase price, tariff, controls and heat demand influence running costs. Efficient conversion alone does not guarantee cheap heating.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A 1 kW panel heater operating continuously for one hour uses about 1 kWh of electricity.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-pump\" data-mwh-related=\"heat-pump\">Heat Pump<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-kilowatt-hour\" data-mwh-related=\"kilowatt-hour\">Kilowatt Hour<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-direct-electric-heating\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-district-heating\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"D\" data-categories=\"heating-hot-water\" data-search=\"District Heating   A system where heat is produced centrally and supplied to multiple homes or buildings through a heat network. A system where heat is produced centrally and supplied to multiple homes or buildings through a heat network.In more detailA type of heat network serving a district or collection of buildings. Heat arrives through insulated pipes and is usually transferred into each property through an interface unit. Charges, metering and heat-source emissions depend on the particular network.A practical exampleSeveral blocks of flats may share heat from one energy centre.Related termsThese are connected ideas, rather than always exact synonyms.Heat NetworkHeat Exchanger\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">District Heating<\/span><span class=\"mwh-entry-short\">A system where heat is produced centrally and supplied to multiple homes or buildings through a heat network.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A system where heat is produced centrally and supplied to multiple homes or buildings through a heat network.<\/p><h3>In more detail<\/h3><p>A type of heat network serving a district or collection of buildings. Heat arrives through insulated pipes and is usually transferred into each property through an interface unit. Charges, metering and heat-source emissions depend on the particular network.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Several blocks of flats may share heat from one energy centre.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-network\" data-mwh-related=\"heat-network\">Heat Network<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-exchanger\" data-mwh-related=\"heat-exchanger\">Heat Exchanger<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-district-heating\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-domestic-energy-assessor\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"D\" data-categories=\"retrofit-standards\" data-search=\"Domestic Energy Assessor DEA DEA A qualified person who produces Energy Performance Certificates for existing homes. A qualified person who produces Energy Performance Certificates for existing homes.Also called: DEAIn more detailAn assessor working with an approved accreditation scheme to produce EPCs for existing dwellings. The role follows a defined assessment method and evidence rules. An EPC visit is not automatically a full building-condition or damp survey.A practical exampleAn assessor may use documentary evidence to record insulation concealed within a roof.Related termsThese are connected ideas, rather than always exact synonyms.Energy Performance CertificateRdSAP\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Domestic Energy Assessor <span class=\"mwh-entry-acronym\">DEA<\/span><\/span><span class=\"mwh-entry-short\">A qualified person who produces Energy Performance Certificates for existing homes.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A qualified person who produces Energy Performance Certificates for existing homes.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> DEA<\/p><h3>In more detail<\/h3><p>An assessor working with an approved accreditation scheme to produce EPCs for existing dwellings. The role follows a defined assessment method and evidence rules. An EPC visit is not automatically a full building-condition or damp survey.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An assessor may use documentary evidence to record insulation concealed within a roof.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-energy-performance-certificate\" data-mwh-related=\"energy-performance-certificate\">Energy Performance Certificate<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-rdsap\" data-mwh-related=\"rdsap\">RdSAP<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-domestic-energy-assessor\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-domestic-hot-water\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"D\" data-categories=\"heating-hot-water\" data-search=\"Domestic Hot Water DHW DHW Hot water used for taps, baths and showers. Hot water used for taps, baths and showers.Also called: DHWIn more detailWater used for washing, bathing and other hot taps, as distinct from the water circulating inside a radiator circuit. Storage temperatures, hygiene controls and safe delivery temperatures are design matters for a competent installer.A practical exampleThe cylinder stores domestic hot water while separate pipework circulates heating water through radiators.Related termsThese are connected ideas, rather than always exact synonyms.Hot Water CylinderSpace Heating\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Domestic Hot Water <span class=\"mwh-entry-acronym\">DHW<\/span><\/span><span class=\"mwh-entry-short\">Hot water used for taps, baths and showers.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Hot water used for taps, baths and showers.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> DHW<\/p><h3>In more detail<\/h3><p>Water used for washing, bathing and other hot taps, as distinct from the water circulating inside a radiator circuit. Storage temperatures, hygiene controls and safe delivery temperatures are design matters for a competent installer.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>The cylinder stores domestic hot water while separate pipework circulates heating water through radiators.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-hot-water-cylinder\" data-mwh-related=\"hot-water-cylinder\">Hot Water Cylinder<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-space-heating\" data-mwh-related=\"space-heating\">Space Heating<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-domestic-hot-water\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-draught-proofing\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"D\" data-categories=\"building-fabric-insulation\" data-search=\"Draught Proofing   Sealing unwanted gaps around windows, doors, floors and service penetrations to reduce cold draughts and heat loss. Sealing unwanted gaps around windows, doors, floors and service penetrations to reduce cold draughts and heat loss.In more detailTargets unintended air leakage around joints and openings. It should preserve required ventilation, combustion air and drainage routes. The correct seal must suit the location and allow intended movement or operation of the component.A practical exampleA properly fitted loft-hatch seal can reduce leakage without blocking a bathroom extract duct.Related termsThese are connected ideas, rather than always exact synonyms.Air TightnessBackground Ventilation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Draught Proofing<\/span><span class=\"mwh-entry-short\">Sealing unwanted gaps around windows, doors, floors and service penetrations to reduce cold draughts and heat loss.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Sealing unwanted gaps around windows, doors, floors and service penetrations to reduce cold draughts and heat loss.<\/p><h3>In more detail<\/h3><p>Targets unintended air leakage around joints and openings. It should preserve required ventilation, combustion air and drainage routes. The correct seal must suit the location and allow intended movement or operation of the component.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A properly fitted loft-hatch seal can reduce leakage without blocking a bathroom extract duct.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-tightness\" data-mwh-related=\"air-tightness\">Air Tightness<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-background-ventilation\" data-mwh-related=\"background-ventilation\">Background Ventilation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-draught-proofing\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"E\" aria-labelledby=\"mwh-letter-E\"><h2 id=\"mwh-letter-E\" class=\"mwh-dictionary-letter\">E<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-eco4\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"E\" data-categories=\"energy-performance\" data-search=\"ECO4   The fourth phase of the Energy Company Obligation, a government energy-efficiency scheme aimed at improving eligible homes. The fourth phase of the Energy Company Obligation, a government energy-efficiency scheme aimed at improving eligible homes.In more detailAn energy-supplier obligation supporting eligible domestic energy-efficiency work in Great Britain, with Ofgem administering the scheme. It is not an automatic entitlement to a free installation. Current deadlines, funding availability and household\/property eligibility must be checked before committing.A practical exampleAn assessment may identify a package of measures rather than a single advertised product.Related termsThese are connected ideas, rather than always exact synonyms.Retrofit AssessmentWhole-House ApproachFurther reading: Ofgem: current ECO guidance. Check current guidance for schemes and standards.\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">ECO4<\/span><span class=\"mwh-entry-short\">The fourth phase of the Energy Company Obligation, a government energy-efficiency scheme aimed at improving eligible homes.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The fourth phase of the Energy Company Obligation, a government energy-efficiency scheme aimed at improving eligible homes.<\/p><h3>In more detail<\/h3><p>An energy-supplier obligation supporting eligible domestic energy-efficiency work in Great Britain, with Ofgem administering the scheme. It is not an automatic entitlement to a free installation. Current deadlines, funding availability and household\/property eligibility must be checked before committing.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An assessment may identify a package of measures rather than a single advertised product.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-assessment\" data-mwh-related=\"retrofit-assessment\">Retrofit Assessment<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-whole-house-approach\" data-mwh-related=\"whole-house-approach\">Whole-House Approach<\/a><\/div><\/nav><p class=\"mwh-entry-source\">Further reading: <a href=\"https:\/\/www.ofgem.gov.uk\/environmental-and-social-schemes\/energy-company-obligation-eco\">Ofgem: current ECO guidance<\/a>. Check current guidance for schemes and standards.<\/p><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-eco4\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-emitter\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"E\" data-categories=\"heating-hot-water\" data-search=\"Emitter   A device that gives heat into a room, such as a radiator, underfloor heating loop, fan coil or convector. A device that gives heat into a room, such as a radiator, underfloor heating loop, fan coil or convector.In more detailTransfers heat from the system into a room. Its output depends on size, design, water and air temperatures, and sometimes a fan. A radiator&#039;s catalogue output may be quoted at hotter conditions than a heat-pump system will use.A practical exampleThe same radiator gives less heat when supplied with cooler water.Related termsThese are connected ideas, rather than always exact synonyms.RadiatorEmitter Sizing\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Emitter<\/span><span class=\"mwh-entry-short\">A device that gives heat into a room, such as a radiator, underfloor heating loop, fan coil or convector.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A device that gives heat into a room, such as a radiator, underfloor heating loop, fan coil or convector.<\/p><h3>In more detail<\/h3><p>Transfers heat from the system into a room. Its output depends on size, design, water and air temperatures, and sometimes a fan. A radiator&#039;s catalogue output may be quoted at hotter conditions than a heat-pump system will use.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>The same radiator gives less heat when supplied with cooler water.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-radiator\" data-mwh-related=\"radiator\">Radiator<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-emitter-sizing\" data-mwh-related=\"emitter-sizing\">Emitter Sizing<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-emitter\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-emitter-sizing\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"E\" data-categories=\"heating-hot-water\" data-search=\"Emitter Sizing   The process of checking whether radiators or underfloor heating can deliver enough heat at the chosen flow temperature. The process of checking whether radiators or underfloor heating can deliver enough heat at the chosen flow temperature.In more detailMatches each room&#039;s heat requirement to an emitter at the proposed operating temperatures. Pipework and available flow also matter. Checking only the radiator&#039;s physical dimensions or its output at boiler conditions can be misleading.A practical exampleA bedroom radiator may need changing while the larger living-room radiator can remain.Related termsThese are connected ideas, rather than always exact synonyms.Room-by-Room Heat LossDesign Flow Temperature\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Emitter Sizing<\/span><span class=\"mwh-entry-short\">The process of checking whether radiators or underfloor heating can deliver enough heat at the chosen flow temperature.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The process of checking whether radiators or underfloor heating can deliver enough heat at the chosen flow temperature.<\/p><h3>In more detail<\/h3><p>Matches each room&#039;s heat requirement to an emitter at the proposed operating temperatures. Pipework and available flow also matter. Checking only the radiator&#039;s physical dimensions or its output at boiler conditions can be misleading.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A bedroom radiator may need changing while the larger living-room radiator can remain.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-room-by-room-heat-loss\" data-mwh-related=\"room-by-room-heat-loss\">Room-by-Room Heat Loss<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-design-flow-temperature\" data-mwh-related=\"design-flow-temperature\">Design Flow Temperature<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-emitter-sizing\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-energy-efficiency\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"E\" data-categories=\"ventilation-air-quality\" data-search=\"Energy Efficiency   Using less energy to achieve the same result, such as heating a home to a comfortable temperature with lower energy use. Using less energy to achieve the same result, such as heating a home to a comfortable temperature with lower energy use.In more detailCompares the useful service obtained with the energy used. A lower-energy home should still provide adequate warmth, fresh air and hot water. Efficiency, total consumption, energy price and carbon emissions are related but are not the same measurement.A practical exampleImproved insulation can reduce the energy needed to maintain the same indoor temperature.Related termsThese are connected ideas, rather than always exact synonyms.Heat DemandDecarbonisation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Energy Efficiency<\/span><span class=\"mwh-entry-short\">Using less energy to achieve the same result, such as heating a home to a comfortable temperature with lower energy use.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Using less energy to achieve the same result, such as heating a home to a comfortable temperature with lower energy use.<\/p><h3>In more detail<\/h3><p>Compares the useful service obtained with the energy used. A lower-energy home should still provide adequate warmth, fresh air and hot water. Efficiency, total consumption, energy price and carbon emissions are related but are not the same measurement.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Improved insulation can reduce the energy needed to maintain the same indoor temperature.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-demand\" data-mwh-related=\"heat-demand\">Heat Demand<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-decarbonisation\" data-mwh-related=\"decarbonisation\">Decarbonisation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-energy-efficiency\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-energy-performance-certificate\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"E\" data-categories=\"energy-performance\" data-search=\"Energy Performance Certificate EPC EPC A certificate that rates a property\u2019s energy performance from A to G and gives recommendations for improvement. A certificate that rates a property\u2019s energy performance from A to G and gives recommendations for improvement.Also called: EPCIn more detailProvides a standardised assessment and improvement recommendations using recorded building data and prescribed assumptions. It is not calculated from the household&#039;s actual bills and is not a guarantee of running costs. Check the date and underlying descriptions before relying on it.A practical exampleInsulation fitted after the assessment will not automatically appear on the old certificate.Related termsThese are connected ideas, rather than always exact synonyms.Domestic Energy AssessorRdSAPFurther reading: Government: domestic EPCs. Check current guidance for schemes and standards.\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Energy Performance Certificate <span class=\"mwh-entry-acronym\">EPC<\/span><\/span><span class=\"mwh-entry-short\">A certificate that rates a property\u2019s energy performance from A to G and gives recommendations for improvement.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A certificate that rates a property\u2019s energy performance from A to G and gives recommendations for improvement.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> EPC<\/p><h3>In more detail<\/h3><p>Provides a standardised assessment and improvement recommendations using recorded building data and prescribed assumptions. It is not calculated from the household&#039;s actual bills and is not a guarantee of running costs. Check the date and underlying descriptions before relying on it.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Insulation fitted after the assessment will not automatically appear on the old certificate.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-domestic-energy-assessor\" data-mwh-related=\"domestic-energy-assessor\">Domestic Energy Assessor<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-rdsap\" data-mwh-related=\"rdsap\">RdSAP<\/a><\/div><\/nav><p class=\"mwh-entry-source\">Further reading: <a href=\"https:\/\/www.gov.uk\/government\/publications\/energy-performance-certificates-for-the-construction-sale-and-let-of-dwellings\/a-guide-to-energy-performance-certificates-for-the-marketing-sale-and-let-of-dwellings\">Government: domestic EPCs<\/a>. Check current guidance for schemes and standards.<\/p><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-energy-performance-certificate\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-energy-saving-measure\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"E\" data-categories=\"controls\" data-search=\"Energy Saving Measure ESM ESM A retrofit improvement designed to reduce energy use, such as insulation, heating controls, glazing or low-carbon heating. A retrofit improvement designed to reduce energy use, such as insulation, heating controls, glazing or low-carbon heating.Also called: ESMIn more detailAn individual improvement intended to reduce energy use. Suitability depends on the building and its other systems. A measure can affect ventilation, moisture and future work, so its place in a whole-house plan matters.A practical exampleLoft insulation may be appropriate, with ventilation routes and the loft hatch addressed at the same time.Related termsThese are connected ideas, rather than always exact synonyms.Whole-House ApproachSpecification\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Energy Saving Measure <span class=\"mwh-entry-acronym\">ESM<\/span><\/span><span class=\"mwh-entry-short\">A retrofit improvement designed to reduce energy use, such as insulation, heating controls, glazing or low-carbon heating.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A retrofit improvement designed to reduce energy use, such as insulation, heating controls, glazing or low-carbon heating.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> ESM<\/p><h3>In more detail<\/h3><p>An individual improvement intended to reduce energy use. Suitability depends on the building and its other systems. A measure can affect ventilation, moisture and future work, so its place in a whole-house plan matters.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Loft insulation may be appropriate, with ventilation routes and the loft hatch addressed at the same time.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-whole-house-approach\" data-mwh-related=\"whole-house-approach\">Whole-House Approach<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-specification\" data-mwh-related=\"specification\">Specification<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-energy-saving-measure\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-expansion-valve\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"E\" data-categories=\"heating-hot-water\" data-search=\"Expansion Valve   In a heat pump or refrigeration cycle, the expansion valve reduces the refrigerant pressure and temperature before it enters the evaporator. In a heat pump or refrigeration cycle, the expansion valve reduces the refrigerant pressure and temperature before it enters the evaporator.In more detailControls refrigerant entering the low-pressure side of the cycle. The pressure drop enables evaporation at a low temperature. This is a specialist refrigerant component, not a homeowner heating-water adjustment valve.A practical exampleA heat pump meters refrigerant through the valve before heat is absorbed at the evaporator.Related termsThese are connected ideas, rather than always exact synonyms.RefrigerantRefrigeration Cycle\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Expansion Valve<\/span><span class=\"mwh-entry-short\">In a heat pump or refrigeration cycle, the expansion valve reduces the refrigerant pressure and temperature before it enters the evaporator.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">In a heat pump or refrigeration cycle, the expansion valve reduces the refrigerant pressure and temperature before it enters the evaporator.<\/p><h3>In more detail<\/h3><p>Controls refrigerant entering the low-pressure side of the cycle. The pressure drop enables evaporation at a low temperature. This is a specialist refrigerant component, not a homeowner heating-water adjustment valve.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A heat pump meters refrigerant through the valve before heat is absorbed at the evaporator.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-refrigerant\" data-mwh-related=\"refrigerant\">Refrigerant<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-refrigeration-cycle\" data-mwh-related=\"refrigeration-cycle\">Refrigeration Cycle<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-expansion-valve\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-expansion-vessel\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"E\" data-categories=\"heating-hot-water\" data-search=\"Expansion Vessel   A vessel in a sealed heating system that absorbs expansion as water heats up. A vessel in a sealed heating system that absorbs expansion as water heats up.In more detailContains a compressible gas cushion separated from water, usually by a diaphragm. It accommodates water expanding as it heats. Pressure problems need proper diagnosis; repeatedly topping up a system is not a repair for a failed vessel or leak.A practical exampleA sealed heating system&#039;s pressure rises excessively when an expansion vessel stops working correctly.Related termsThese are connected ideas, rather than always exact synonyms.Pressure Relief ValveCommissioning\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Expansion Vessel<\/span><span class=\"mwh-entry-short\">A vessel in a sealed heating system that absorbs expansion as water heats up.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A vessel in a sealed heating system that absorbs expansion as water heats up.<\/p><h3>In more detail<\/h3><p>Contains a compressible gas cushion separated from water, usually by a diaphragm. It accommodates water expanding as it heats. Pressure problems need proper diagnosis; repeatedly topping up a system is not a repair for a failed vessel or leak.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A sealed heating system&#039;s pressure rises excessively when an expansion vessel stops working correctly.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-pressure-relief-valve\" data-mwh-related=\"pressure-relief-valve\">Pressure Relief Valve<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-commissioning\" data-mwh-related=\"commissioning\">Commissioning<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-expansion-vessel\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-external-wall-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"E\" data-categories=\"moisture-damp\" data-search=\"External Wall Insulation EWI EWI Insulation fixed to the outside of external walls and finished with render, cladding or another weatherproof layer. Insulation fixed to the outside of external walls and finished with render, cladding or another weatherproof layer.Also called: EWIIn more detailWraps the outside of a wall with insulation and a protective finish. Eaves, window reveals, services, ground levels and water shedding require careful detailing. The existing wall&#039;s condition and moisture behaviour must be understood before it is covered.A practical exampleA design may extend sills so rainwater clears the new thicker wall face.Related termsThese are connected ideas, rather than always exact synonyms.Internal Wall InsulationWindow Reveal\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">External Wall Insulation <span class=\"mwh-entry-acronym\">EWI<\/span><\/span><span class=\"mwh-entry-short\">Insulation fixed to the outside of external walls and finished with render, cladding or another weatherproof layer.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Insulation fixed to the outside of external walls and finished with render, cladding or another weatherproof layer.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> EWI<\/p><h3>In more detail<\/h3><p>Wraps the outside of a wall with insulation and a protective finish. Eaves, window reveals, services, ground levels and water shedding require careful detailing. The existing wall&#039;s condition and moisture behaviour must be understood before it is covered.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A design may extend sills so rainwater clears the new thicker wall face.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-internal-wall-insulation\" data-mwh-related=\"internal-wall-insulation\">Internal Wall Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-window-reveal\" data-mwh-related=\"window-reveal\">Window Reveal<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-external-wall-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-extractor-fan\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"E\" data-categories=\"energy-performance\" data-search=\"Extractor Fan   A fan that removes moist or stale air from rooms such as bathrooms, kitchens and utility rooms. A fan that removes moist or stale air from rooms such as bathrooms, kitchens and utility rooms.In more detailRemoves indoor air through ducting to outdoors or an appropriate extract system. A fan making a noise does not prove adequate airflow. Duct size, bends, grilles, replacement air and maintenance can all influence actual performance.A practical exampleA bathroom fan with a crushed duct may remove little moisture despite appearing to run normally.Related termsThese are connected ideas, rather than always exact synonyms.CommissioningWet Room Extract\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Extractor Fan<\/span><span class=\"mwh-entry-short\">A fan that removes moist or stale air from rooms such as bathrooms, kitchens and utility rooms.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A fan that removes moist or stale air from rooms such as bathrooms, kitchens and utility rooms.<\/p><h3>In more detail<\/h3><p>Removes indoor air through ducting to outdoors or an appropriate extract system. A fan making a noise does not prove adequate airflow. Duct size, bends, grilles, replacement air and maintenance can all influence actual performance.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A bathroom fan with a crushed duct may remove little moisture despite appearing to run normally.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-commissioning\" data-mwh-related=\"commissioning\">Commissioning<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-wet-room-extract\" data-mwh-related=\"wet-room-extract\">Wet Room Extract<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-extractor-fan\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"F\" aria-labelledby=\"mwh-letter-F\"><h2 id=\"mwh-letter-F\" class=\"mwh-dictionary-letter\">F<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-f-gas\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"F\" data-categories=\"heating-hot-water\" data-search=\"F-Gas   Fluorinated greenhouse gas used in some refrigeration, air conditioning and heat pump systems. Fluorinated greenhouse gas used in some refrigeration, air conditioning and heat pump systems. Some F-gases have high global warming potential.In more detailA family of fluorinated gases, including some refrigerants, rather than one specific substance. Environmental impact and rules depend on the gas and equipment. Installation, servicing and disposal should be handled by appropriately qualified people under the applicable requirements.A practical exampleTwo heat pumps can use different refrigerants with very different global-warming potentials.Related termsThese are connected ideas, rather than always exact synonyms.RefrigerantGlobal Warming Potential\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">F-Gas<\/span><span class=\"mwh-entry-short\">Fluorinated greenhouse gas used in some refrigeration, air conditioning and heat pump systems.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Fluorinated greenhouse gas used in some refrigeration, air conditioning and heat pump systems. Some F-gases have high global warming potential.<\/p><h3>In more detail<\/h3><p>A family of fluorinated gases, including some refrigerants, rather than one specific substance. Environmental impact and rules depend on the gas and equipment. Installation, servicing and disposal should be handled by appropriately qualified people under the applicable requirements.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Two heat pumps can use different refrigerants with very different global-warming potentials.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-refrigerant\" data-mwh-related=\"refrigerant\">Refrigerant<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-global-warming-potential\" data-mwh-related=\"global-warming-potential\">Global Warming Potential<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-f-gas\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-fabric-first\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"F\" data-categories=\"ventilation-air-quality\" data-search=\"Fabric First   Planning improvements to the building fabric and ventilation alongside heating, to reduce avoidable heat demand and support a suitable system design. Planning improvements to the building fabric and ventilation alongside heating, to reduce avoidable heat demand and support a suitable system design.In more detailPrioritises reducing avoidable heat loss and addressing the building&#039;s condition before final equipment sizing. It is a planning principle, not a rule that every insulation measure must happen before a heating replacement. Ventilation and moisture need consideration throughout.A practical exampleA heat-loss calculation is updated after planned insulation so a new heat pump is not oversized.Related termsThese are connected ideas, rather than always exact synonyms.Building FabricWhole-House Approach\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Fabric First<\/span><span class=\"mwh-entry-short\">Planning improvements to the building fabric and ventilation alongside heating, to reduce avoidable heat demand and support a suitable system design.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Planning improvements to the building fabric and ventilation alongside heating, to reduce avoidable heat demand and support a suitable system design.<\/p><h3>In more detail<\/h3><p>Prioritises reducing avoidable heat loss and addressing the building&#039;s condition before final equipment sizing. It is a planning principle, not a rule that every insulation measure must happen before a heating replacement. Ventilation and moisture need consideration throughout.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A heat-loss calculation is updated after planned insulation so a new heat pump is not oversized.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-building-fabric\" data-mwh-related=\"building-fabric\">Building Fabric<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-whole-house-approach\" data-mwh-related=\"whole-house-approach\">Whole-House Approach<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-fabric-first\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-fan-coil-unit\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"F\" data-categories=\"heating-hot-water\" data-search=\"Fan Coil Unit   A heat emitter that uses a fan to move air across a heating or cooling coil. A heat emitter that uses a fan to move air across a heating or cooling coil.In more detailUses a fan to move room air over a heat-exchange coil. Fan speed, water temperature, noise and airflow affect output and comfort. A recirculating fan coil does not necessarily supply outdoor ventilation air.A practical exampleA compact fan-assisted emitter can provide useful heating at lower water temperatures.Related termsThese are connected ideas, rather than always exact synonyms.EmitterLow Temperature Heating\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Fan Coil Unit<\/span><span class=\"mwh-entry-short\">A heat emitter that uses a fan to move air across a heating or cooling coil.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A heat emitter that uses a fan to move air across a heating or cooling coil.<\/p><h3>In more detail<\/h3><p>Uses a fan to move room air over a heat-exchange coil. Fan speed, water temperature, noise and airflow affect output and comfort. A recirculating fan coil does not necessarily supply outdoor ventilation air.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A compact fan-assisted emitter can provide useful heating at lower water temperatures.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-emitter\" data-mwh-related=\"emitter\">Emitter<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-low-temperature-heating\" data-mwh-related=\"low-temperature-heating\">Low Temperature Heating<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-fan-coil-unit\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-flat-roof-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"F\" data-categories=\"building-fabric-insulation\" data-search=\"Flat Roof Insulation   Insulation added to a flat roof. Insulation added to a flat roof. It may be installed above, below or within the roof structure depending on the roof type.In more detailThe insulation position determines whether the roof is described as warm, cold or another build-up. Condensation control, drainage and waterproofing must be designed together. Adding insulation underneath an existing roof without checking the build-up can create moisture risks.A practical exampleA warm-roof refurbishment places insulation above the structural deck as part of a coordinated system.Related termsThese are connected ideas, rather than always exact synonyms.Warm RoofVapour Control Layer\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Flat Roof Insulation<\/span><span class=\"mwh-entry-short\">Insulation added to a flat roof.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Insulation added to a flat roof. It may be installed above, below or within the roof structure depending on the roof type.<\/p><h3>In more detail<\/h3><p>The insulation position determines whether the roof is described as warm, cold or another build-up. Condensation control, drainage and waterproofing must be designed together. Adding insulation underneath an existing roof without checking the build-up can create moisture risks.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A warm-roof refurbishment places insulation above the structural deck as part of a coordinated system.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-warm-roof\" data-mwh-related=\"warm-roof\">Warm Roof<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-vapour-control-layer\" data-mwh-related=\"vapour-control-layer\">Vapour Control Layer<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flat-roof-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-floor-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"F\" data-categories=\"building-fabric-insulation\" data-search=\"Floor Insulation   Insulation added to solid floors, suspended timber floors or between floor joists to reduce heat loss. Insulation added to solid floors, suspended timber floors or between floor joists to reduce heat loss.In more detailReduces heat transfer through the lowest exposed floor or a floor over an unheated space. Solid and suspended floors need different methods. Ground moisture, ventilation, services, thresholds and finished floor levels can limit the options.A practical exampleInsulation below timber boards must preserve any required ventilation of the floor void.Related termsThese are connected ideas, rather than always exact synonyms.Solid Floor InsulationSuspended Timber Floor\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Floor Insulation<\/span><span class=\"mwh-entry-short\">Insulation added to solid floors, suspended timber floors or between floor joists to reduce heat loss.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Insulation added to solid floors, suspended timber floors or between floor joists to reduce heat loss.<\/p><h3>In more detail<\/h3><p>Reduces heat transfer through the lowest exposed floor or a floor over an unheated space. Solid and suspended floors need different methods. Ground moisture, ventilation, services, thresholds and finished floor levels can limit the options.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Insulation below timber boards must preserve any required ventilation of the floor void.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solid-floor-insulation\" data-mwh-related=\"solid-floor-insulation\">Solid Floor Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-suspended-timber-floor\" data-mwh-related=\"suspended-timber-floor\">Suspended Timber Floor<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-floor-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-flow-rate\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"F\" data-categories=\"heating-hot-water\" data-search=\"Flow Rate   The amount of water moving through a heating system over a set time. The amount of water moving through a heating system over a set time.In more detailDescribes the volume or mass of water moving in a given time, often litres per minute. Heat transfer depends on both flow and the temperature difference between supply and return. Bigger pump settings are not automatically better.A practical exampleInsufficient water flow can limit a heat pump even when its nominal output is large enough.Related termsThese are connected ideas, rather than always exact synonyms.Flow TemperatureReturn Temperature\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Flow Rate<\/span><span class=\"mwh-entry-short\">The amount of water moving through a heating system over a set time.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The amount of water moving through a heating system over a set time.<\/p><h3>In more detail<\/h3><p>Describes the volume or mass of water moving in a given time, often litres per minute. Heat transfer depends on both flow and the temperature difference between supply and return. Bigger pump settings are not automatically better.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Insufficient water flow can limit a heat pump even when its nominal output is large enough.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flow-temperature\" data-mwh-related=\"flow-temperature\">Flow Temperature<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-return-temperature\" data-mwh-related=\"return-temperature\">Return Temperature<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flow-rate\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-flow-temperature\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"F\" data-categories=\"heating-hot-water\" data-search=\"Flow Temperature   The temperature of water leaving a boiler or heat pump to supply radiators, underfloor heating or hot water systems. The temperature of water leaving a boiler or heat pump to supply radiators, underfloor heating or hot water systems.In more detailThe supply temperature leaving the heat source for a particular circuit. It can change with controls and demand. Hot-water cylinder heating may require a different operating temperature from room heating, so the two should not be confused.A practical exampleWeather compensation lowers radiator flow temperature during milder outdoor conditions.Related termsThese are connected ideas, rather than always exact synonyms.Design Flow TemperatureReturn Temperature\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Flow Temperature<\/span><span class=\"mwh-entry-short\">The temperature of water leaving a boiler or heat pump to supply radiators, underfloor heating or hot water systems.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The temperature of water leaving a boiler or heat pump to supply radiators, underfloor heating or hot water systems.<\/p><h3>In more detail<\/h3><p>The supply temperature leaving the heat source for a particular circuit. It can change with controls and demand. Hot-water cylinder heating may require a different operating temperature from room heating, so the two should not be confused.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Weather compensation lowers radiator flow temperature during milder outdoor conditions.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-design-flow-temperature\" data-mwh-related=\"design-flow-temperature\">Design Flow Temperature<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-return-temperature\" data-mwh-related=\"return-temperature\">Return Temperature<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flow-temperature\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-flue\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"F\" data-categories=\"heating-hot-water\" data-search=\"Flue   A pipe or duct that safely removes combustion gases from a boiler, stove or fire. A pipe or duct that safely removes combustion gases from a boiler, stove or fire.In more detailCarries combustion products to a safe discharge point. It differs from an extractor duct or a chimney used only for ventilation. Changes to terminals, liners or nearby construction require specialist assessment for the appliance concerned.A practical exampleInsulation work near a boiler terminal must maintain the specified clearances.Related termsThese are connected ideas, rather than always exact synonyms.Balanced FlueCombustion Ventilation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Flue<\/span><span class=\"mwh-entry-short\">A pipe or duct that safely removes combustion gases from a boiler, stove or fire.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A pipe or duct that safely removes combustion gases from a boiler, stove or fire.<\/p><h3>In more detail<\/h3><p>Carries combustion products to a safe discharge point. It differs from an extractor duct or a chimney used only for ventilation. Changes to terminals, liners or nearby construction require specialist assessment for the appliance concerned.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Insulation work near a boiler terminal must maintain the specified clearances.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-balanced-flue\" data-mwh-related=\"balanced-flue\">Balanced Flue<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-combustion-ventilation\" data-mwh-related=\"combustion-ventilation\">Combustion Ventilation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flue\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-fuel-poverty\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"F\" data-categories=\"heating-hot-water\" data-search=\"Fuel Poverty   A situation where a household struggles to afford adequate heating and energy services. A situation where a household struggles to afford adequate heating and energy services.In more detailDescribes difficulty obtaining adequate energy services at an affordable cost; formal definitions vary across the UK. Poor efficiency, household income and energy costs can all contribute. It should not be confused with simply choosing to use less heating.A practical exampleA poorly insulated home may be expensive to keep warm even with careful use of the controls.Related termsThese are connected ideas, rather than always exact synonyms.Energy EfficiencyHeat Demand\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Fuel Poverty<\/span><span class=\"mwh-entry-short\">A situation where a household struggles to afford adequate heating and energy services.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A situation where a household struggles to afford adequate heating and energy services.<\/p><h3>In more detail<\/h3><p>Describes difficulty obtaining adequate energy services at an affordable cost; formal definitions vary across the UK. Poor efficiency, household income and energy costs can all contribute. It should not be confused with simply choosing to use less heating.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A poorly insulated home may be expensive to keep warm even with careful use of the controls.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-energy-efficiency\" data-mwh-related=\"energy-efficiency\">Energy Efficiency<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-demand\" data-mwh-related=\"heat-demand\">Heat Demand<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-fuel-poverty\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"G\" aria-labelledby=\"mwh-letter-G\"><h2 id=\"mwh-letter-G\" class=\"mwh-dictionary-letter\">G<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-gas-boiler\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"G\" data-categories=\"heating-hot-water\" data-search=\"Gas Boiler   A boiler that burns mains gas to provide heating and hot water. A boiler that burns mains gas to provide heating and hot water.In more detailBurns mains gas and transfers heat to water. Condensing operation depends partly on return-water temperature. Installation and servicing need a suitably qualified Gas Safe registered engineer; controls and system condition affect real performance.A practical exampleA modulating boiler reduces its burner output as the home approaches the set temperature.Related termsThese are connected ideas, rather than always exact synonyms.BoilerReturn Temperature\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Gas Boiler<\/span><span class=\"mwh-entry-short\">A boiler that burns mains gas to provide heating and hot water.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A boiler that burns mains gas to provide heating and hot water.<\/p><h3>In more detail<\/h3><p>Burns mains gas and transfers heat to water. Condensing operation depends partly on return-water temperature. Installation and servicing need a suitably qualified Gas Safe registered engineer; controls and system condition affect real performance.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A modulating boiler reduces its burner output as the home approaches the set temperature.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-boiler\" data-mwh-related=\"boiler\">Boiler<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-return-temperature\" data-mwh-related=\"return-temperature\">Return Temperature<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-gas-boiler\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-glazing\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"G\" data-categories=\"building-fabric-insulation\" data-search=\"Glazing   The glass part of a window or door. The glass part of a window or door. Double and triple glazing reduce heat loss compared with single glazing.In more detailIncludes the glass panes and their coatings, cavities and spacers. Whole-window performance also includes the frame and installation. Double glazing can vary considerably, so compare appropriate whole-window specifications rather than counting panes alone.A practical exampleA draught around a frame may persist even when the glass unit is high performance.Related termsThese are connected ideas, rather than always exact synonyms.Secondary GlazingU-Value\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Glazing<\/span><span class=\"mwh-entry-short\">The glass part of a window or door.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The glass part of a window or door. Double and triple glazing reduce heat loss compared with single glazing.<\/p><h3>In more detail<\/h3><p>Includes the glass panes and their coatings, cavities and spacers. Whole-window performance also includes the frame and installation. Double glazing can vary considerably, so compare appropriate whole-window specifications rather than counting panes alone.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A draught around a frame may persist even when the glass unit is high performance.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-secondary-glazing\" data-mwh-related=\"secondary-glazing\">Secondary Glazing<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-u-value\" data-mwh-related=\"u-value\">U-Value<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-glazing\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-global-warming-potential\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"G\" data-categories=\"energy-performance\" data-search=\"Global Warming Potential GWP GWP A measure of how much heat a greenhouse gas traps in the atmosphere compared with carbon dioxide. A measure of how much heat a greenhouse gas traps in the atmosphere compared with carbon dioxide.Also called: GWPIn more detailCompares a greenhouse gas&#039;s warming effect with carbon dioxide over a stated time horizon, commonly 100 years. For refrigerants, the amount leaked also matters. A low GWP figure does not describe the equipment&#039;s electricity consumption.A practical exampleA small leak of a high-GWP refrigerant can have a greater climate effect than the same mass of a low-GWP gas.Related termsThese are connected ideas, rather than always exact synonyms.F-GasRefrigerant\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Global Warming Potential <span class=\"mwh-entry-acronym\">GWP<\/span><\/span><span class=\"mwh-entry-short\">A measure of how much heat a greenhouse gas traps in the atmosphere compared with carbon dioxide.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A measure of how much heat a greenhouse gas traps in the atmosphere compared with carbon dioxide.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> GWP<\/p><h3>In more detail<\/h3><p>Compares a greenhouse gas&#039;s warming effect with carbon dioxide over a stated time horizon, commonly 100 years. For refrigerants, the amount leaked also matters. A low GWP figure does not describe the equipment&#039;s electricity consumption.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A small leak of a high-GWP refrigerant can have a greater climate effect than the same mass of a low-GWP gas.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-f-gas\" data-mwh-related=\"f-gas\">F-Gas<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-refrigerant\" data-mwh-related=\"refrigerant\">Refrigerant<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-global-warming-potential\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-ground-loop\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"G\" data-categories=\"heating-hot-water\" data-search=\"Ground Loop   Pipework buried in the ground that collects heat for a ground source heat pump. Pipework buried in the ground that collects heat for a ground source heat pump.In more detailCirculates a heat-transfer fluid through buried pipes to collect ground heat. Horizontal trenches and vertical boreholes have different space and design requirements. The ground collector must be sized for the building and local conditions.A practical exampleA horizontal collector needs suitable land area, while a borehole system needs specialist drilling.Related termsThese are connected ideas, rather than always exact synonyms.Ground Source Heat PumpHeat Exchanger\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Ground Loop<\/span><span class=\"mwh-entry-short\">Pipework buried in the ground that collects heat for a ground source heat pump.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Pipework buried in the ground that collects heat for a ground source heat pump.<\/p><h3>In more detail<\/h3><p>Circulates a heat-transfer fluid through buried pipes to collect ground heat. Horizontal trenches and vertical boreholes have different space and design requirements. The ground collector must be sized for the building and local conditions.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A horizontal collector needs suitable land area, while a borehole system needs specialist drilling.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ground-source-heat-pump\" data-mwh-related=\"ground-source-heat-pump\">Ground Source Heat Pump<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-exchanger\" data-mwh-related=\"heat-exchanger\">Heat Exchanger<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ground-loop\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-ground-source-heat-pump\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"G\" data-categories=\"heating-hot-water\" data-search=\"Ground Source Heat Pump GSHP GSHP A heat pump that collects heat from the ground using buried pipework, boreholes or collector loops. A heat pump that collects heat from the ground using buried pipework, boreholes or collector loops.Also called: GSHPIn more detailMoves heat collected from the ground into the home using electricity. The collector, heat pump and indoor distribution must be designed as one system. Ground temperatures are steadier than outdoor air, but installation feasibility is site-specific.A practical exampleA borehole collector can serve a property without enough land for horizontal trenches.Related termsThese are connected ideas, rather than always exact synonyms.Ground LoopHeat Pump\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Ground Source Heat Pump <span class=\"mwh-entry-acronym\">GSHP<\/span><\/span><span class=\"mwh-entry-short\">A heat pump that collects heat from the ground using buried pipework, boreholes or collector loops.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A heat pump that collects heat from the ground using buried pipework, boreholes or collector loops.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> GSHP<\/p><h3>In more detail<\/h3><p>Moves heat collected from the ground into the home using electricity. The collector, heat pump and indoor distribution must be designed as one system. Ground temperatures are steadier than outdoor air, but installation feasibility is site-specific.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A borehole collector can serve a property without enough land for horizontal trenches.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ground-loop\" data-mwh-related=\"ground-loop\">Ground Loop<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-pump\" data-mwh-related=\"heat-pump\">Heat Pump<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ground-source-heat-pump\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"H\" aria-labelledby=\"mwh-letter-H\"><h2 id=\"mwh-letter-H\" class=\"mwh-dictionary-letter\">H<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-hard-to-treat-property\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"building-fabric-insulation\" data-search=\"Hard-to-Treat Property   A home that is more complex or costly to improve, often because of solid walls, unusual construction, access issues or heritage restrictions. A home that is more complex or costly to improve, often because of solid walls, unusual construction, access issues or heritage restrictions.In more detailA descriptive phrase for practical improvement difficulties, not a diagnosis that the home cannot be improved. Construction, exposure, access and heritage significance may call for different measures or specialist design.A practical exampleAn older solid-wall terrace may need a carefully designed internal insulation approach instead of cavity fill.Related termsThese are connected ideas, rather than always exact synonyms.Solid WallRetrofit Assessment\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Hard-to-Treat Property<\/span><span class=\"mwh-entry-short\">A home that is more complex or costly to improve, often because of solid walls, unusual construction, access issues or heritage restrictions.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A home that is more complex or costly to improve, often because of solid walls, unusual construction, access issues or heritage restrictions.<\/p><h3>In more detail<\/h3><p>A descriptive phrase for practical improvement difficulties, not a diagnosis that the home cannot be improved. Construction, exposure, access and heritage significance may call for different measures or specialist design.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An older solid-wall terrace may need a carefully designed internal insulation approach instead of cavity fill.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solid-wall\" data-mwh-related=\"solid-wall\">Solid Wall<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-assessment\" data-mwh-related=\"retrofit-assessment\">Retrofit Assessment<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-hard-to-treat-property\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-heat-demand\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"energy-performance\" data-search=\"Heat Demand   The amount of heat needed to keep a home or room at the desired temperature. The amount of heat needed to keep a home or room at the desired temperature.In more detailCan mean energy needed over a period, normally in kWh, whereas a design heating load is power in kW. Always check the units. Demand changes with weather, temperature settings, building condition and occupancy.A practical exampleAnnual heat demand helps estimate energy use; peak heating load helps size equipment.Related termsThese are connected ideas, rather than always exact synonyms.Design Heat LossKilowatt Hour\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Heat Demand<\/span><span class=\"mwh-entry-short\">The amount of heat needed to keep a home or room at the desired temperature.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The amount of heat needed to keep a home or room at the desired temperature.<\/p><h3>In more detail<\/h3><p>Can mean energy needed over a period, normally in kWh, whereas a design heating load is power in kW. Always check the units. Demand changes with weather, temperature settings, building condition and occupancy.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Annual heat demand helps estimate energy use; peak heating load helps size equipment.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-design-heat-loss\" data-mwh-related=\"design-heat-loss\">Design Heat Loss<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-kilowatt-hour\" data-mwh-related=\"kilowatt-hour\">Kilowatt Hour<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-demand\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-heat-exchanger\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"energy-performance\" data-search=\"Heat Exchanger   A component that transfers heat from one fluid or gas to another without mixing them. A component that transfers heat from one fluid or gas to another without mixing them.In more detailTransfers heat across a separating surface. The fluids normally remain separate, although the detailed arrangement varies. Surface area, cleanliness and temperature differences affect how effectively it works.A practical exampleA cylinder coil transfers heat from heating water into the stored tap water without mixing them.Related termsThese are connected ideas, rather than always exact synonyms.Hot Water CylinderCondenser\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Heat Exchanger<\/span><span class=\"mwh-entry-short\">A component that transfers heat from one fluid or gas to another without mixing them.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A component that transfers heat from one fluid or gas to another without mixing them.<\/p><h3>In more detail<\/h3><p>Transfers heat across a separating surface. The fluids normally remain separate, although the detailed arrangement varies. Surface area, cleanliness and temperature differences affect how effectively it works.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A cylinder coil transfers heat from heating water into the stored tap water without mixing them.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-hot-water-cylinder\" data-mwh-related=\"hot-water-cylinder\">Hot Water Cylinder<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-condenser\" data-mwh-related=\"condenser\">Condenser<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-exchanger\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-heat-loss\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"ventilation-air-quality\" data-search=\"Heat Loss   The amount of heat escaping from a property through walls, roofs, floors, windows, doors, ventilation and draughts. The amount of heat escaping from a property through walls, roofs, floors, windows, doors, ventilation and draughts.In more detailIncludes heat passing through the fabric and heat carried away by air exchange. The rate rises as the difference between indoor and outdoor temperature grows. Good design considers both routes and the required ventilation.A practical exampleA room loses more heat on a freezing day than on a mild day at the same indoor temperature.Related termsThese are connected ideas, rather than always exact synonyms.Heat Loss CalculationVentilation Heat Loss\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Heat Loss<\/span><span class=\"mwh-entry-short\">The amount of heat escaping from a property through walls, roofs, floors, windows, doors, ventilation and draughts.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The amount of heat escaping from a property through walls, roofs, floors, windows, doors, ventilation and draughts.<\/p><h3>In more detail<\/h3><p>Includes heat passing through the fabric and heat carried away by air exchange. The rate rises as the difference between indoor and outdoor temperature grows. Good design considers both routes and the required ventilation.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A room loses more heat on a freezing day than on a mild day at the same indoor temperature.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-loss-calculation\" data-mwh-related=\"heat-loss-calculation\">Heat Loss Calculation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ventilation-heat-loss\" data-mwh-related=\"ventilation-heat-loss\">Ventilation Heat Loss<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-loss\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-heat-loss-calculation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"heating-hot-water\" data-search=\"Heat Loss Calculation   A calculation used to estimate how much heat a property or room loses. A calculation used to estimate how much heat a property or room loses. It is essential for sizing heat pumps and radiators correctly.In more detailUses dimensions, construction, temperatures and air-change assumptions to estimate heating load. A useful report states its inputs and limitations. Floor area alone or a boiler&#039;s previous rating is not a substitute for a proper calculation.A practical exampleDifferent rooms in the same house may require very different radiator outputs.Related termsThese are connected ideas, rather than always exact synonyms.Room-by-Room Heat LossDesign Heat Loss\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Heat Loss Calculation<\/span><span class=\"mwh-entry-short\">A calculation used to estimate how much heat a property or room loses.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A calculation used to estimate how much heat a property or room loses. It is essential for sizing heat pumps and radiators correctly.<\/p><h3>In more detail<\/h3><p>Uses dimensions, construction, temperatures and air-change assumptions to estimate heating load. A useful report states its inputs and limitations. Floor area alone or a boiler&#039;s previous rating is not a substitute for a proper calculation.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Different rooms in the same house may require very different radiator outputs.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-room-by-room-heat-loss\" data-mwh-related=\"room-by-room-heat-loss\">Room-by-Room Heat Loss<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-design-heat-loss\" data-mwh-related=\"design-heat-loss\">Design Heat Loss<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-loss-calculation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-heat-network\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"heating-hot-water\" data-search=\"Heat Network   A system that distributes heat from a central source to multiple buildings or homes. A system that distributes heat from a central source to multiple buildings or homes.In more detailDistributes heat from shared sources to more than one customer or building. Networks can use different fuels and technologies. The network&#039;s source, losses, service arrangements and charging structure determine its practical and environmental performance.A practical exampleA block of flats can share a plant room rather than each flat having an individual boiler.Related termsThese are connected ideas, rather than always exact synonyms.District HeatingHeat Exchanger\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Heat Network<\/span><span class=\"mwh-entry-short\">A system that distributes heat from a central source to multiple buildings or homes.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A system that distributes heat from a central source to multiple buildings or homes.<\/p><h3>In more detail<\/h3><p>Distributes heat from shared sources to more than one customer or building. Networks can use different fuels and technologies. The network&#039;s source, losses, service arrangements and charging structure determine its practical and environmental performance.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A block of flats can share a plant room rather than each flat having an individual boiler.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-district-heating\" data-mwh-related=\"district-heating\">District Heating<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-exchanger\" data-mwh-related=\"heat-exchanger\">Heat Exchanger<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-network\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-heat-pump\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"heating-hot-water\" data-search=\"Heat Pump   A low-carbon heating system that moves heat from outside air, the ground or water and upgrades it for space heating and hot water. A low-carbon heating system that moves heat from outside air, the ground or water and upgrades it for space heating and hot water.In more detailUses a refrigerant cycle and electricity to move heat, rather than generating all the heat directly from electricity. Its performance depends on source temperature, required delivery temperature, sizing and controls.A practical exampleFor suitable conditions, electrical input of 1 kWh can move several kWh of heat into a home.Related termsThese are connected ideas, rather than always exact synonyms.Air Source Heat PumpCoefficient of Performance\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Heat Pump<\/span><span class=\"mwh-entry-short\">A low-carbon heating system that moves heat from outside air, the ground or water and upgrades it for space heating and hot water.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A low-carbon heating system that moves heat from outside air, the ground or water and upgrades it for space heating and hot water.<\/p><h3>In more detail<\/h3><p>Uses a refrigerant cycle and electricity to move heat, rather than generating all the heat directly from electricity. Its performance depends on source temperature, required delivery temperature, sizing and controls.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>For suitable conditions, electrical input of 1 kWh can move several kWh of heat into a home.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-source-heat-pump\" data-mwh-related=\"air-source-heat-pump\">Air Source Heat Pump<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-coefficient-of-performance\" data-mwh-related=\"coefficient-of-performance\">Coefficient of Performance<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-pump\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-heating-controls\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"controls\" data-search=\"Heating Controls   Devices that control when and how heating operates, including thermostats, programmers, TRVs, smart controls and weather compensation. Devices that control when and how heating operates, including thermostats, programmers, TRVs, smart controls and weather compensation.In more detailCoordinate heat-source operation and room comfort. Room thermostats, radiator valves and compensation controls perform different tasks. They should work together without unnecessarily restricting required system flow or repeatedly switching the heat source.A practical exampleA well-set weather curve can maintain comfort without using an unnecessarily high radiator temperature.Related termsThese are connected ideas, rather than always exact synonyms.ThermostatWeather Compensation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Heating Controls<\/span><span class=\"mwh-entry-short\">Devices that control when and how heating operates, including thermostats, programmers, TRVs, smart controls and weather compensation.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Devices that control when and how heating operates, including thermostats, programmers, TRVs, smart controls and weather compensation.<\/p><h3>In more detail<\/h3><p>Coordinate heat-source operation and room comfort. Room thermostats, radiator valves and compensation controls perform different tasks. They should work together without unnecessarily restricting required system flow or repeatedly switching the heat source.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A well-set weather curve can maintain comfort without using an unnecessarily high radiator temperature.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermostat\" data-mwh-related=\"thermostat\">Thermostat<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-weather-compensation\" data-mwh-related=\"weather-compensation\">Weather Compensation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heating-controls\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-heating-curve\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"controls\" data-search=\"Heating Curve   A control setting that changes the heat pump flow temperature depending on the outside temperature. A control setting that changes the heat pump flow temperature depending on the outside temperature.In more detailDefines how the target water temperature changes as outdoor temperature changes. Slope and offset have different effects. Adjustment should be gradual and informed by comfort and system guidance, rather than copying another home&#039;s settings.A practical exampleIf all rooms become too cool only in colder weather, the curve&#039;s slope may need review.Related termsThese are connected ideas, rather than always exact synonyms.Weather CompensationDesign Flow Temperature\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Heating Curve<\/span><span class=\"mwh-entry-short\">A control setting that changes the heat pump flow temperature depending on the outside temperature.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A control setting that changes the heat pump flow temperature depending on the outside temperature.<\/p><h3>In more detail<\/h3><p>Defines how the target water temperature changes as outdoor temperature changes. Slope and offset have different effects. Adjustment should be gradual and informed by comfort and system guidance, rather than copying another home&#039;s settings.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>If all rooms become too cool only in colder weather, the curve&#039;s slope may need review.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-weather-compensation\" data-mwh-related=\"weather-compensation\">Weather Compensation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-design-flow-temperature\" data-mwh-related=\"design-flow-temperature\">Design Flow Temperature<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heating-curve\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-high-heat-retention-storage-heater\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"controls\" data-search=\"High Heat Retention Storage Heater   An improved type of electric storage heater that stores heat more efficiently and releases it in a more controlled way. An improved type of electric storage heater that stores heat more efficiently and releases it in a more controlled way.In more detailUses insulated storage and controlled heat release to make better use of stored off-peak electricity. Charging controls and tariff compatibility matter. It still uses direct electric resistance heating rather than the heat-moving process of a heat pump.A practical exampleThe heater charges overnight and releases controlled heat later, according to its settings and available stored energy.Related termsThese are connected ideas, rather than always exact synonyms.Direct Electric HeatingHeating Controls\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">High Heat Retention Storage Heater<\/span><span class=\"mwh-entry-short\">An improved type of electric storage heater that stores heat more efficiently and releases it in a more controlled way.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">An improved type of electric storage heater that stores heat more efficiently and releases it in a more controlled way.<\/p><h3>In more detail<\/h3><p>Uses insulated storage and controlled heat release to make better use of stored off-peak electricity. Charging controls and tariff compatibility matter. It still uses direct electric resistance heating rather than the heat-moving process of a heat pump.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>The heater charges overnight and releases controlled heat later, according to its settings and available stored energy.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-direct-electric-heating\" data-mwh-related=\"direct-electric-heating\">Direct Electric Heating<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heating-controls\" data-mwh-related=\"heating-controls\">Heating Controls<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-high-heat-retention-storage-heater\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-hot-water-cylinder\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"heating-hot-water\" data-search=\"Hot Water Cylinder   A tank that stores hot water for taps, baths and showers. A tank that stores hot water for taps, baths and showers. Heat pumps usually need a compatible hot water cylinder.In more detailStores potable hot water, with heating provided through a coil, immersion heater or another arrangement. Volume, coil size, insulation and reheating time matter. It is not the same as an expansion vessel or a heating buffer.A practical exampleA heat pump may require a cylinder with a larger compatible heat-exchange coil than an older boiler system.Related termsThese are connected ideas, rather than always exact synonyms.Domestic Hot WaterHeat Exchanger\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Hot Water Cylinder<\/span><span class=\"mwh-entry-short\">A tank that stores hot water for taps, baths and showers.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A tank that stores hot water for taps, baths and showers. Heat pumps usually need a compatible hot water cylinder.<\/p><h3>In more detail<\/h3><p>Stores potable hot water, with heating provided through a coil, immersion heater or another arrangement. Volume, coil size, insulation and reheating time matter. It is not the same as an expansion vessel or a heating buffer.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A heat pump may require a cylinder with a larger compatible heat-exchange coil than an older boiler system.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-domestic-hot-water\" data-mwh-related=\"domestic-hot-water\">Domestic Hot Water<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-exchanger\" data-mwh-related=\"heat-exchanger\">Heat Exchanger<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-hot-water-cylinder\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-hybrid-heating-system\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"heating-hot-water\" data-search=\"Hybrid Heating System   A heating system that combines two technologies, such as a heat pump and a gas boiler. A heating system that combines two technologies, such as a heat pump and a gas boiler.In more detailCombines heat sources with controls deciding when each operates. Design should explain changeover conditions, running costs, emissions and maintenance needs. Having two heat sources does not automatically produce the most efficient arrangement.A practical exampleA controller may use a heat pump for much of the year and a boiler for selected conditions.Related termsThese are connected ideas, rather than always exact synonyms.Heat PumpHeating Controls\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Hybrid Heating System<\/span><span class=\"mwh-entry-short\">A heating system that combines two technologies, such as a heat pump and a gas boiler.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A heating system that combines two technologies, such as a heat pump and a gas boiler.<\/p><h3>In more detail<\/h3><p>Combines heat sources with controls deciding when each operates. Design should explain changeover conditions, running costs, emissions and maintenance needs. Having two heat sources does not automatically produce the most efficient arrangement.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A controller may use a heat pump for much of the year and a boiler for selected conditions.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-pump\" data-mwh-related=\"heat-pump\">Heat Pump<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heating-controls\" data-mwh-related=\"heating-controls\">Heating Controls<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-hybrid-heating-system\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-hydrobox\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"\" data-search=\"Hydrobox   An indoor heat-pump module containing hydraulic components; the exact equipment inside depends on the system. An indoor heat-pump module containing hydraulic components; the exact equipment inside depends on the system.In more detailAn indoor hydraulic module used in some heat-pump arrangements. It may contain a heat exchanger, pump and controls, but contents vary by manufacturer. The term describes a package of components, not a separate heat source.A practical exampleA split heat pump can have outdoor refrigerant equipment connected to an indoor hydrobox serving the water circuit.Related termsThese are connected ideas, rather than always exact synonyms.Split SystemHeat Exchanger\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Hydrobox<\/span><span class=\"mwh-entry-short\">An indoor heat-pump module containing hydraulic components; the exact equipment inside depends on the system.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">An indoor heat-pump module containing hydraulic components; the exact equipment inside depends on the system.<\/p><h3>In more detail<\/h3><p>An indoor hydraulic module used in some heat-pump arrangements. It may contain a heat exchanger, pump and controls, but contents vary by manufacturer. The term describes a package of components, not a separate heat source.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A split heat pump can have outdoor refrigerant equipment connected to an indoor hydrobox serving the water circuit.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-split-system\" data-mwh-related=\"split-system\">Split System<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-exchanger\" data-mwh-related=\"heat-exchanger\">Heat Exchanger<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-hydrobox\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-hygrothermal-assessment\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"H\" data-categories=\"\" data-search=\"hygrothermal assessment   An engineering analysis that tracks how heat and moisture move simultaneously through building walls, roofs, or floors An engineering analysis that tracks how heat and moisture move simultaneously through building walls, roofs, or floorsIn more detailExamines how heat and moisture behave together within a construction over time. The accuracy depends on material properties, weather, indoor conditions and assumptions. It helps evaluate risks but cannot compensate for poor detailing or water leaks.A practical exampleA designer may assess moisture behaviour before insulating an older solid wall internally.Related termsThese are connected ideas, rather than always exact synonyms.Moisture BalanceInternal Wall Insulation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">hygrothermal assessment<\/span><span class=\"mwh-entry-short\">An engineering analysis that tracks how heat and moisture move simultaneously through building walls, roofs, or floors<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">An engineering analysis that tracks how heat and moisture move simultaneously through building walls, roofs, or floors<\/p><h3>In more detail<\/h3><p>Examines how heat and moisture behave together within a construction over time. The accuracy depends on material properties, weather, indoor conditions and assumptions. It helps evaluate risks but cannot compensate for poor detailing or water leaks.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A designer may assess moisture behaviour before insulating an older solid wall internally.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-moisture-balance\" data-mwh-related=\"moisture-balance\">Moisture Balance<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-internal-wall-insulation\" data-mwh-related=\"internal-wall-insulation\">Internal Wall Insulation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-hygrothermal-assessment\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"I\" aria-labelledby=\"mwh-letter-I\"><h2 id=\"mwh-letter-I\" class=\"mwh-dictionary-letter\">I<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-indoor-air-quality\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"I\" data-categories=\"ventilation-air-quality\" data-search=\"Indoor Air Quality IAQ IAQ The quality of the air inside a home. The quality of the air inside a home. It can be affected by moisture, ventilation, pollutants, mould, combustion appliances and occupancy.Also called: IAQIn more detailReflects airborne pollutants and moisture, not just whether air smells fresh. Ventilation, source control and maintenance all matter. A home can be warm and energy efficient yet still need better extraction or fresh-air provision.A practical exampleCooking pollutants and shower moisture need suitable removal even after draughts have been reduced.Related termsThese are connected ideas, rather than always exact synonyms.VentilationWet Room Extract\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Indoor Air Quality <span class=\"mwh-entry-acronym\">IAQ<\/span><\/span><span class=\"mwh-entry-short\">The quality of the air inside a home.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The quality of the air inside a home. It can be affected by moisture, ventilation, pollutants, mould, combustion appliances and occupancy.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> IAQ<\/p><h3>In more detail<\/h3><p>Reflects airborne pollutants and moisture, not just whether air smells fresh. Ventilation, source control and maintenance all matter. A home can be warm and energy efficient yet still need better extraction or fresh-air provision.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Cooking pollutants and shower moisture need suitable removal even after draughts have been reduced.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ventilation\" data-mwh-related=\"ventilation\">Ventilation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-wet-room-extract\" data-mwh-related=\"wet-room-extract\">Wet Room Extract<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-indoor-air-quality\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-infrared-heating\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"I\" data-categories=\"heating-hot-water\" data-search=\"Infrared Heating   Electric heating panels that warm people and surfaces directly using radiant heat. Electric heating panels that warm people and surfaces directly using radiant heat.In more detailUses radiant heat to warm surfaces and people in its field of view. Room air is also warmed indirectly. It remains direct electric heating; comfort effects do not mean that every unit of electricity creates several units of heat.A practical exampleA radiant panel can warm someone nearby, but its location and room heat loss still affect comfort.Related termsThese are connected ideas, rather than always exact synonyms.Direct Electric HeatingEmitter\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Infrared Heating<\/span><span class=\"mwh-entry-short\">Electric heating panels that warm people and surfaces directly using radiant heat.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Electric heating panels that warm people and surfaces directly using radiant heat.<\/p><h3>In more detail<\/h3><p>Uses radiant heat to warm surfaces and people in its field of view. Room air is also warmed indirectly. It remains direct electric heating; comfort effects do not mean that every unit of electricity creates several units of heat.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A radiant panel can warm someone nearby, but its location and room heat loss still affect comfort.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-direct-electric-heating\" data-mwh-related=\"direct-electric-heating\">Direct Electric Heating<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-emitter\" data-mwh-related=\"emitter\">Emitter<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-infrared-heating\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-insulated-plasterboard\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"I\" data-categories=\"building-fabric-insulation\" data-search=\"Insulated Plasterboard   Plasterboard with insulation bonded to the back. Plasterboard with insulation bonded to the back. It is often used internally on walls or ceilings.In more detailCombines plasterboard with an insulation layer. Thermal performance depends on thickness, material and installation. Joints, fixings, services and moisture-control details need proper design; the board alone is not a complete wall-insulation specification.A practical exampleUninsulated window reveals can remain cold even when the main wall has insulated plasterboard.Related termsThese are connected ideas, rather than always exact synonyms.Internal Wall InsulationWindow Reveal\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Insulated Plasterboard<\/span><span class=\"mwh-entry-short\">Plasterboard with insulation bonded to the back.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Plasterboard with insulation bonded to the back. It is often used internally on walls or ceilings.<\/p><h3>In more detail<\/h3><p>Combines plasterboard with an insulation layer. Thermal performance depends on thickness, material and installation. Joints, fixings, services and moisture-control details need proper design; the board alone is not a complete wall-insulation specification.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Uninsulated window reveals can remain cold even when the main wall has insulated plasterboard.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-internal-wall-insulation\" data-mwh-related=\"internal-wall-insulation\">Internal Wall Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-window-reveal\" data-mwh-related=\"window-reveal\">Window Reveal<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-insulated-plasterboard\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"I\" data-categories=\"building-fabric-insulation\" data-search=\"Insulation   Material used to slow down heat loss. Material used to slow down heat loss. Common examples include mineral wool, PIR, phenolic board, EPS, XPS, wood fibre, hemp, sheep\u2019s wool and cellulose.In more detailSlows heat transfer rather than creating heat. The installed thickness, continuity, moisture condition and detailing influence results. Materials vary in fire, moisture, acoustic and structural properties as well as thermal conductivity.A practical exampleA gap at the edge of an otherwise well-insulated loft can leave a local cold area.Related termsThese are connected ideas, rather than always exact synonyms.Thermal ConductivityThermal Bridge\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Insulation<\/span><span class=\"mwh-entry-short\">Material used to slow down heat loss.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Material used to slow down heat loss. Common examples include mineral wool, PIR, phenolic board, EPS, XPS, wood fibre, hemp, sheep\u2019s wool and cellulose.<\/p><h3>In more detail<\/h3><p>Slows heat transfer rather than creating heat. The installed thickness, continuity, moisture condition and detailing influence results. Materials vary in fire, moisture, acoustic and structural properties as well as thermal conductivity.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A gap at the edge of an otherwise well-insulated loft can leave a local cold area.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-conductivity\" data-mwh-related=\"thermal-conductivity\">Thermal Conductivity<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-bridge\" data-mwh-related=\"thermal-bridge\">Thermal Bridge<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-intermittent-extract-fan\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"I\" data-categories=\"ventilation-air-quality\" data-search=\"Intermittent Extract Fan   A fan that runs when needed, usually when a bathroom or kitchen is being used. A fan that runs when needed, usually when a bathroom or kitchen is being used.In more detailRuns in response to a switch, humidity sensor or other demand signal. An overrun may continue extraction afterwards. It needs an adequate air path and effective outdoor discharge; short operation or obstructed ducting can limit moisture removal.A practical exampleA bathroom fan continues after the light is switched off to remove remaining moist air.Related termsThese are connected ideas, rather than always exact synonyms.Extractor FanBackground Ventilation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Intermittent Extract Fan<\/span><span class=\"mwh-entry-short\">A fan that runs when needed, usually when a bathroom or kitchen is being used.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A fan that runs when needed, usually when a bathroom or kitchen is being used.<\/p><h3>In more detail<\/h3><p>Runs in response to a switch, humidity sensor or other demand signal. An overrun may continue extraction afterwards. It needs an adequate air path and effective outdoor discharge; short operation or obstructed ducting can limit moisture removal.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A bathroom fan continues after the light is switched off to remove remaining moist air.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-extractor-fan\" data-mwh-related=\"extractor-fan\">Extractor Fan<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-background-ventilation\" data-mwh-related=\"background-ventilation\">Background Ventilation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-intermittent-extract-fan\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-internal-wall-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"I\" data-categories=\"moisture-damp\" data-search=\"Internal Wall Insulation IWI IWI Insulation fitted to the inside face of external walls. Insulation fitted to the inside face of external walls. It can improve thermal performance but must be designed carefully to manage moisture risk.Also called: IWIIn more detailAdds an insulating lining inside an external wall. It reduces room space and changes the wall&#039;s temperature and moisture behaviour. Junctions, services, airtightness and drying potential require coordinated design, especially for older solid-wall construction.A practical exampleAn internal lining must meet the window reveal and floor junction without leaving avoidable cold bridges.Related termsThese are connected ideas, rather than always exact synonyms.External Wall Insulationhygrothermal assessment\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Internal Wall Insulation <span class=\"mwh-entry-acronym\">IWI<\/span><\/span><span class=\"mwh-entry-short\">Insulation fitted to the inside face of external walls.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Insulation fitted to the inside face of external walls. It can improve thermal performance but must be designed carefully to manage moisture risk.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> IWI<\/p><h3>In more detail<\/h3><p>Adds an insulating lining inside an external wall. It reduces room space and changes the wall&#039;s temperature and moisture behaviour. Junctions, services, airtightness and drying potential require coordinated design, especially for older solid-wall construction.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An internal lining must meet the window reveal and floor junction without leaving avoidable cold bridges.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-external-wall-insulation\" data-mwh-related=\"external-wall-insulation\">External Wall Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-hygrothermal-assessment\" data-mwh-related=\"hygrothermal-assessment\">hygrothermal assessment<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-internal-wall-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-inverter-compressor\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"I\" data-categories=\"heating-hot-water\" data-search=\"Inverter Compressor   A variable-speed compressor used in many heat pumps. A variable-speed compressor used in many heat pumps. It can adjust output to match demand more efficiently.In more detailVaries compressor speed to adjust heating output within its operating range. It cannot reduce output indefinitely. Correct sizing, water volume, flow and controls still matter to avoid excessive cycling at low demand.A practical exampleA heat pump may run gently in mild weather instead of repeatedly switching fully on and off.Related termsThese are connected ideas, rather than always exact synonyms.Heat PumpVolumiser\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Inverter Compressor<\/span><span class=\"mwh-entry-short\">A variable-speed compressor used in many heat pumps.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A variable-speed compressor used in many heat pumps. It can adjust output to match demand more efficiently.<\/p><h3>In more detail<\/h3><p>Varies compressor speed to adjust heating output within its operating range. It cannot reduce output indefinitely. Correct sizing, water volume, flow and controls still matter to avoid excessive cycling at low demand.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A heat pump may run gently in mild weather instead of repeatedly switching fully on and off.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-pump\" data-mwh-related=\"heat-pump\">Heat Pump<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-volumiser\" data-mwh-related=\"volumiser\">Volumiser<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-inverter-compressor\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"J\" aria-labelledby=\"mwh-letter-J\"><h2 id=\"mwh-letter-J\" class=\"mwh-dictionary-letter\">J<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-junction\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"J\" data-categories=\"building-fabric-insulation\" data-search=\"Junction   A point where building elements meet, such as wall-to-roof, wall-to-floor or window-to-wall. A point where building elements meet, such as wall-to-roof, wall-to-floor or window-to-wall. Junctions are important for heat loss and thermal bridging.In more detailA meeting point between elements with potentially different thermal and moisture behaviour. Continuity of insulation, airtightness and rain protection needs attention here. A well-insulated main surface can still lose heat through a poorly detailed junction.A practical exampleThe wall-to-roof connection should continue the insulation without obstructing required ventilation.Related termsThese are connected ideas, rather than always exact synonyms.Thermal BridgeService Penetration\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Junction<\/span><span class=\"mwh-entry-short\">A point where building elements meet, such as wall-to-roof, wall-to-floor or window-to-wall.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A point where building elements meet, such as wall-to-roof, wall-to-floor or window-to-wall. Junctions are important for heat loss and thermal bridging.<\/p><h3>In more detail<\/h3><p>A meeting point between elements with potentially different thermal and moisture behaviour. Continuity of insulation, airtightness and rain protection needs attention here. A well-insulated main surface can still lose heat through a poorly detailed junction.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>The wall-to-roof connection should continue the insulation without obstructing required ventilation.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-bridge\" data-mwh-related=\"thermal-bridge\">Thermal Bridge<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-service-penetration\" data-mwh-related=\"service-penetration\">Service Penetration<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-junction\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"K\" aria-labelledby=\"mwh-letter-K\"><h2 id=\"mwh-letter-K\" class=\"mwh-dictionary-letter\">K<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-kilowatt\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"K\" data-categories=\"heating-hot-water\" data-search=\"Kilowatt kW kW A unit of power. A unit of power. Heating system output is usually measured in kilowatts.Also called: kWIn more detailA unit of power equal to 1,000 watts: the rate of using, generating or transferring energy. It does not describe energy used over a whole day. Keep kW separate from kWh when reading equipment specifications and bills.A practical exampleA heater rated at 2 kW uses energy twice as fast as a 1 kW heater while both run at full output.Related termsThese are connected ideas, rather than always exact synonyms.Kilowatt HourPeak Load\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Kilowatt <span class=\"mwh-entry-acronym\">kW<\/span><\/span><span class=\"mwh-entry-short\">A unit of power.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A unit of power. Heating system output is usually measured in kilowatts.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> kW<\/p><h3>In more detail<\/h3><p>A unit of power equal to 1,000 watts: the rate of using, generating or transferring energy. It does not describe energy used over a whole day. Keep kW separate from kWh when reading equipment specifications and bills.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A heater rated at 2 kW uses energy twice as fast as a 1 kW heater while both run at full output.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-kilowatt-hour\" data-mwh-related=\"kilowatt-hour\">Kilowatt Hour<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-peak-load\" data-mwh-related=\"peak-load\">Peak Load<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-kilowatt\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-kilowatt-hour\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"K\" data-categories=\"energy-performance\" data-search=\"Kilowatt Hour kWh kWh A unit of energy. A unit of energy. Energy bills usually charge for electricity or gas in kWh.Also called: kWhIn more detailThe energy transferred by a power of one kilowatt acting for one hour. Bills use this unit for energy quantity. Actual consumption depends on operating time and power, which can vary during use.A practical exampleA 2 kW heater running continuously for half an hour uses 1 kWh.Related termsThese are connected ideas, rather than always exact synonyms.KilowattEnergy Efficiency\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Kilowatt Hour <span class=\"mwh-entry-acronym\">kWh<\/span><\/span><span class=\"mwh-entry-short\">A unit of energy.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A unit of energy. Energy bills usually charge for electricity or gas in kWh.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> kWh<\/p><h3>In more detail<\/h3><p>The energy transferred by a power of one kilowatt acting for one hour. Bills use this unit for energy quantity. Actual consumption depends on operating time and power, which can vary during use.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A 2 kW heater running continuously for half an hour uses 1 kWh.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-kilowatt\" data-mwh-related=\"kilowatt\">Kilowatt<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-energy-efficiency\" data-mwh-related=\"energy-efficiency\">Energy Efficiency<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-kilowatt-hour\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"L\" aria-labelledby=\"mwh-letter-L\"><h2 id=\"mwh-letter-L\" class=\"mwh-dictionary-letter\">L<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-lambda-value\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"L\" data-categories=\"building-fabric-insulation\" data-search=\"Lambda Value   A measure of a material\u2019s thermal conductivity. A measure of a material\u2019s thermal conductivity. Lower lambda values mean the material is better at resisting heat flow.In more detailAnother name for thermal conductivity, commonly written as the Greek letter lambda and measured in W\/(m\u00b7K). Lower values mean less heat flows through the material for comparable dimensions. Thickness is still needed to calculate resistance.A practical exampleA thinner layer with a lower lambda can provide similar resistance to a thicker layer with a higher lambda.Related termsThese are connected ideas, rather than always exact synonyms.Thermal ConductivityR-Value\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Lambda Value<\/span><span class=\"mwh-entry-short\">A measure of a material\u2019s thermal conductivity.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A measure of a material\u2019s thermal conductivity. Lower lambda values mean the material is better at resisting heat flow.<\/p><h3>In more detail<\/h3><p>Another name for thermal conductivity, commonly written as the Greek letter lambda and measured in W\/(m\u00b7K). Lower values mean less heat flows through the material for comparable dimensions. Thickness is still needed to calculate resistance.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A thinner layer with a lower lambda can provide similar resistance to a thicker layer with a higher lambda.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-conductivity\" data-mwh-related=\"thermal-conductivity\">Thermal Conductivity<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-r-value\" data-mwh-related=\"r-value\">R-Value<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-lambda-value\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-lime-plaster\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"L\" data-categories=\"building-fabric-insulation\" data-search=\"Lime Plaster   A traditional breathable plaster often used in older solid-wall buildings. A traditional breathable plaster often used in older solid-wall buildings.In more detailA lime-based internal finish used in many traditional buildings. Its moisture behaviour depends on the mix and coatings. Suitable finishes can support drying, but lime plaster is not a cure for an active leak or defective drainage.A practical exampleCovering lime plaster with an impermeable coating may alter the wall&#039;s ability to dry.Related termsThese are connected ideas, rather than always exact synonyms.BreathabilitySolid Wall\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Lime Plaster<\/span><span class=\"mwh-entry-short\">A traditional breathable plaster often used in older solid-wall buildings.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A traditional breathable plaster often used in older solid-wall buildings.<\/p><h3>In more detail<\/h3><p>A lime-based internal finish used in many traditional buildings. Its moisture behaviour depends on the mix and coatings. Suitable finishes can support drying, but lime plaster is not a cure for an active leak or defective drainage.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Covering lime plaster with an impermeable coating may alter the wall&#039;s ability to dry.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-breathability\" data-mwh-related=\"breathability\">Breathability<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solid-wall\" data-mwh-related=\"solid-wall\">Solid Wall<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-lime-plaster\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-listed-building\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"L\" data-categories=\"retrofit-standards\" data-search=\"Listed Building   A building protected because of its special architectural or historic interest. A building protected because of its special architectural or historic interest. Retrofit work may need special permissions and sensitive design.In more detailA building protected for special architectural or historic interest. Works affecting its character may require listed-building consent, separately from planning permission and building regulations. Obtain advice for the particular building and proposed changes.A practical exampleReplacing historic windows can require consent even when the replacement is more energy efficient.Related termsThese are connected ideas, rather than always exact synonyms.Conservation AreaPlanning Permission\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Listed Building<\/span><span class=\"mwh-entry-short\">A building protected because of its special architectural or historic interest.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A building protected because of its special architectural or historic interest. Retrofit work may need special permissions and sensitive design.<\/p><h3>In more detail<\/h3><p>A building protected for special architectural or historic interest. Works affecting its character may require listed-building consent, separately from planning permission and building regulations. Obtain advice for the particular building and proposed changes.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Replacing historic windows can require consent even when the replacement is more energy efficient.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-conservation-area\" data-mwh-related=\"conservation-area\">Conservation Area<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-planning-permission\" data-mwh-related=\"planning-permission\">Planning Permission<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-listed-building\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-loft-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"L\" data-categories=\"building-fabric-insulation\" data-search=\"Loft Insulation   Insulation installed at ceiling level or roof level to reduce heat loss through the roof. Insulation installed at ceiling level or roof level to reduce heat loss through the roof.In more detailAt ceiling level it usually keeps the rooms warm while the loft remains outside the heated envelope. Roof-slope insulation creates a different arrangement. Ventilation, water tanks, wiring, downlights and access need suitable detailing.A practical exampleA loft hatch should be insulated and sealed as part of an otherwise insulated ceiling.Related termsThese are connected ideas, rather than always exact synonyms.Thermal EnvelopeVentilation Strategy\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Loft Insulation<\/span><span class=\"mwh-entry-short\">Insulation installed at ceiling level or roof level to reduce heat loss through the roof.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Insulation installed at ceiling level or roof level to reduce heat loss through the roof.<\/p><h3>In more detail<\/h3><p>At ceiling level it usually keeps the rooms warm while the loft remains outside the heated envelope. Roof-slope insulation creates a different arrangement. Ventilation, water tanks, wiring, downlights and access need suitable detailing.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A loft hatch should be insulated and sealed as part of an otherwise insulated ceiling.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-envelope\" data-mwh-related=\"thermal-envelope\">Thermal Envelope<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ventilation-strategy\" data-mwh-related=\"ventilation-strategy\">Ventilation Strategy<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-loft-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-low-carbon-heating\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"L\" data-categories=\"heating-hot-water\" data-search=\"Low Carbon Heating   Heating that produces lower carbon emissions than traditional fossil fuel systems. Heating that produces lower carbon emissions than traditional fossil fuel systems. Examples include heat pumps, heat networks and some biomass systems.In more detailDescribes heating with comparatively lower greenhouse-gas emissions under stated assumptions. The electricity or fuel source, equipment efficiency and demand influence the result. Low carbon does not necessarily mean low purchase price or zero operating emissions.A practical exampleA heat pump&#039;s operational emissions depend partly on the electricity supplying it.Related termsThese are connected ideas, rather than always exact synonyms.DecarbonisationHeat Pump\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Low Carbon Heating<\/span><span class=\"mwh-entry-short\">Heating that produces lower carbon emissions than traditional fossil fuel systems.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Heating that produces lower carbon emissions than traditional fossil fuel systems. Examples include heat pumps, heat networks and some biomass systems.<\/p><h3>In more detail<\/h3><p>Describes heating with comparatively lower greenhouse-gas emissions under stated assumptions. The electricity or fuel source, equipment efficiency and demand influence the result. Low carbon does not necessarily mean low purchase price or zero operating emissions.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A heat pump&#039;s operational emissions depend partly on the electricity supplying it.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-decarbonisation\" data-mwh-related=\"decarbonisation\">Decarbonisation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-pump\" data-mwh-related=\"heat-pump\">Heat Pump<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-low-carbon-heating\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-low-temperature-heating\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"L\" data-categories=\"heating-hot-water\" data-search=\"Low Temperature Heating   A heating system designed to work with lower water temperatures. A heating system designed to work with lower water temperatures. Heat pumps are most efficient when supplying low flow temperatures.In more detailUses water cool enough to improve compatible heat-source performance while still meeting room demand. Emitter area and operating time often need consideration. There is no single suitable water temperature for every building and heating system.A practical exampleLarger emitters can supply the required room heat with cooler circulating water.Related termsThese are connected ideas, rather than always exact synonyms.Emitter SizingDesign Flow Temperature\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Low Temperature Heating<\/span><span class=\"mwh-entry-short\">A heating system designed to work with lower water temperatures.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A heating system designed to work with lower water temperatures. Heat pumps are most efficient when supplying low flow temperatures.<\/p><h3>In more detail<\/h3><p>Uses water cool enough to improve compatible heat-source performance while still meeting room demand. Emitter area and operating time often need consideration. There is no single suitable water temperature for every building and heating system.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Larger emitters can supply the required room heat with cooler circulating water.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-emitter-sizing\" data-mwh-related=\"emitter-sizing\">Emitter Sizing<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-design-flow-temperature\" data-mwh-related=\"design-flow-temperature\">Design Flow Temperature<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-low-temperature-heating\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"M\" aria-labelledby=\"mwh-letter-M\"><h2 id=\"mwh-letter-M\" class=\"mwh-dictionary-letter\">M<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-mechanical-extract-ventilation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"M\" data-categories=\"ventilation-air-quality\" data-search=\"Mechanical Extract Ventilation MEV MEV A ventilation system that continuously extracts air from wet rooms such as kitchens, bathrooms and utility rooms. A ventilation system that continuously extracts air from wet rooms such as kitchens, bathrooms and utility rooms.Also called: MEVIn more detailContinuously removes air from wet rooms, with replacement air entering through planned openings elsewhere. Systems may use a central unit or decentralised fans. Airflow must be measured and balanced with suitable air-transfer routes.A practical exampleContinuous bathroom extraction needs replacement air to reach the bathroom through the dwelling.Related termsThese are connected ideas, rather than always exact synonyms.Background VentilationCommissioning\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Mechanical Extract Ventilation <span class=\"mwh-entry-acronym\">MEV<\/span><\/span><span class=\"mwh-entry-short\">A ventilation system that continuously extracts air from wet rooms such as kitchens, bathrooms and utility rooms.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A ventilation system that continuously extracts air from wet rooms such as kitchens, bathrooms and utility rooms.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> MEV<\/p><h3>In more detail<\/h3><p>Continuously removes air from wet rooms, with replacement air entering through planned openings elsewhere. Systems may use a central unit or decentralised fans. Airflow must be measured and balanced with suitable air-transfer routes.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Continuous bathroom extraction needs replacement air to reach the bathroom through the dwelling.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-background-ventilation\" data-mwh-related=\"background-ventilation\">Background Ventilation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-commissioning\" data-mwh-related=\"commissioning\">Commissioning<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-mechanical-extract-ventilation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-mechanical-ventilation-with-heat-recovery\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"M\" data-categories=\"ventilation-air-quality\" data-search=\"Mechanical Ventilation with Heat Recovery MVHR MVHR A ventilation system that extracts stale air and supplies fresh air while recovering heat from the outgoing air. A ventilation system that extracts stale air and supplies fresh air while recovering heat from the outgoing air.Also called: MVHRIn more detailUses separate supply and extract air paths with a heat exchanger transferring heat between them. It needs designed ductwork, commissioning, filter changes and maintenance. Performance depends on installation quality and the building&#039;s leakage characteristics.A practical exampleOutgoing warm bathroom air preheats fresh incoming air without the two air streams normally mixing.Related termsThese are connected ideas, rather than always exact synonyms.Air TightnessHeat Exchanger\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Mechanical Ventilation with Heat Recovery <span class=\"mwh-entry-acronym\">MVHR<\/span><\/span><span class=\"mwh-entry-short\">A ventilation system that extracts stale air and supplies fresh air while recovering heat from the outgoing air.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A ventilation system that extracts stale air and supplies fresh air while recovering heat from the outgoing air.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> MVHR<\/p><h3>In more detail<\/h3><p>Uses separate supply and extract air paths with a heat exchanger transferring heat between them. It needs designed ductwork, commissioning, filter changes and maintenance. Performance depends on installation quality and the building&#039;s leakage characteristics.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Outgoing warm bathroom air preheats fresh incoming air without the two air streams normally mixing.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-tightness\" data-mwh-related=\"air-tightness\">Air Tightness<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-exchanger\" data-mwh-related=\"heat-exchanger\">Heat Exchanger<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-mechanical-ventilation-with-heat-recovery\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-microgeneration-certification-scheme\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"M\" data-categories=\"renewables-electricity\" data-search=\"Microgeneration Certification Scheme MCS MCS A certification scheme covering low-carbon technologies such as heat pumps, solar PV and battery storage. A certification scheme covering low-carbon technologies such as heat pumps, solar PV and battery storage.Also called: MCSIn more detailProvides certification arrangements for small-scale renewable technologies and installers. Check that the organisation and technology are covered for the work proposed. Certification is useful evidence but does not replace checking the actual design and handover documents.A practical exampleA homeowner can ask for the applicable installation certificate and commissioning information for their heat pump.Related termsThese are connected ideas, rather than always exact synonyms.CommissioningQuality Assurance\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Microgeneration Certification Scheme <span class=\"mwh-entry-acronym\">MCS<\/span><\/span><span class=\"mwh-entry-short\">A certification scheme covering low-carbon technologies such as heat pumps, solar PV and battery storage.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A certification scheme covering low-carbon technologies such as heat pumps, solar PV and battery storage.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> MCS<\/p><h3>In more detail<\/h3><p>Provides certification arrangements for small-scale renewable technologies and installers. Check that the organisation and technology are covered for the work proposed. Certification is useful evidence but does not replace checking the actual design and handover documents.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A homeowner can ask for the applicable installation certificate and commissioning information for their heat pump.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-commissioning\" data-mwh-related=\"commissioning\">Commissioning<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-quality-assurance\" data-mwh-related=\"quality-assurance\">Quality Assurance<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-microgeneration-certification-scheme\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-mineral-wool\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"M\" data-categories=\"building-fabric-insulation\" data-search=\"Mineral Wool   A common insulation material made from glass or rock fibres. A common insulation material made from glass or rock fibres. It is often used in lofts, cavities, floors and walls.In more detailIncludes glass-wool and stone-wool products with different densities and applications. Correct thickness, support and fit are important; compression or gaps can reduce installed performance. Product suitability must be checked for the specific location.A practical exampleA loft roll should fit around obstructions without leaving gaps at the edges.Related termsThese are connected ideas, rather than always exact synonyms.InsulationLoft Insulation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Mineral Wool<\/span><span class=\"mwh-entry-short\">A common insulation material made from glass or rock fibres.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A common insulation material made from glass or rock fibres. It is often used in lofts, cavities, floors and walls.<\/p><h3>In more detail<\/h3><p>Includes glass-wool and stone-wool products with different densities and applications. Correct thickness, support and fit are important; compression or gaps can reduce installed performance. Product suitability must be checked for the specific location.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A loft roll should fit around obstructions without leaving gaps at the edges.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-insulation\" data-mwh-related=\"insulation\">Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-loft-insulation\" data-mwh-related=\"loft-insulation\">Loft Insulation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-mineral-wool\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-moisture-balance\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"M\" data-categories=\"moisture-damp\" data-search=\"Moisture Balance   The relationship between moisture entering, moving through and leaving a building. The relationship between moisture entering, moving through and leaving a building. Poor moisture balance can cause condensation, damp and mould.In more detailLooks at all sources and routes of moisture, including rain, ground water, leaks and indoor humidity, and how the building dries. Improving one route while blocking another can create unexpected problems.A practical exampleInsulation work should not cover a wet wall before the water source and drying strategy are understood.Related termsThese are connected ideas, rather than always exact synonyms.Damphygrothermal assessment\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Moisture Balance<\/span><span class=\"mwh-entry-short\">The relationship between moisture entering, moving through and leaving a building.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The relationship between moisture entering, moving through and leaving a building. Poor moisture balance can cause condensation, damp and mould.<\/p><h3>In more detail<\/h3><p>Looks at all sources and routes of moisture, including rain, ground water, leaks and indoor humidity, and how the building dries. Improving one route while blocking another can create unexpected problems.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Insulation work should not cover a wet wall before the water source and drying strategy are understood.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-damp\" data-mwh-related=\"damp\">Damp<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-hygrothermal-assessment\" data-mwh-related=\"hygrothermal-assessment\">hygrothermal assessment<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-moisture-balance\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-monobloc\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"M\" data-categories=\"\" data-search=\"Monobloc   A monobloc heat pump is an all-in-one heating system where all the main components are housed inside a single outdoor unit. A monobloc heat pump is an all-in-one heating system where all the main components are housed inside a single outdoor unit.In more detailIn an air-to-water arrangement, the main refrigerant components are assembled in the outdoor unit and water pipes normally connect it to the home. External water pipework needs appropriate insulation and frost protection designed for the system.A practical exampleThe installer considers what happens to outdoor pipework during freezing weather or a power interruption.Related termsThese are connected ideas, rather than always exact synonyms.Split SystemHeat Pump\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Monobloc<\/span><span class=\"mwh-entry-short\">A monobloc heat pump is an all-in-one heating system where all the main components are housed inside a single outdoor unit.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A monobloc heat pump is an all-in-one heating system where all the main components are housed inside a single outdoor unit.<\/p><h3>In more detail<\/h3><p>In an air-to-water arrangement, the main refrigerant components are assembled in the outdoor unit and water pipes normally connect it to the home. External water pipework needs appropriate insulation and frost protection designed for the system.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>The installer considers what happens to outdoor pipework during freezing weather or a power interruption.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-split-system\" data-mwh-related=\"split-system\">Split System<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-pump\" data-mwh-related=\"heat-pump\">Heat Pump<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-monobloc\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-mould\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"M\" data-categories=\"ventilation-air-quality\" data-search=\"Mould   Fungal growth that can occur where moisture, poor ventilation and cold surfaces are present. Fungal growth that can occur where moisture, poor ventilation and cold surfaces are present.In more detailFungi can grow on persistently damp surfaces and materials. Colour alone does not identify the species or health risk. Safe removal and investigation of the moisture source are both needed; repeatedly painting over growth does not resolve the cause.A practical exampleA cold bedroom corner may develop mould where high humidity and a low surface temperature coincide.Related termsThese are connected ideas, rather than always exact synonyms.CondensationDamp\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Mould<\/span><span class=\"mwh-entry-short\">Fungal growth that can occur where moisture, poor ventilation and cold surfaces are present.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Fungal growth that can occur where moisture, poor ventilation and cold surfaces are present.<\/p><h3>In more detail<\/h3><p>Fungi can grow on persistently damp surfaces and materials. Colour alone does not identify the species or health risk. Safe removal and investigation of the moisture source are both needed; repeatedly painting over growth does not resolve the cause.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A cold bedroom corner may develop mould where high humidity and a low surface temperature coincide.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-condensation\" data-mwh-related=\"condensation\">Condensation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-damp\" data-mwh-related=\"damp\">Damp<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-mould\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"N\" aria-labelledby=\"mwh-letter-N\"><h2 id=\"mwh-letter-N\" class=\"mwh-dictionary-letter\">N<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-natural-ventilation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"N\" data-categories=\"ventilation-air-quality\" data-search=\"Natural Ventilation   Ventilation driven by wind and temperature differences, usually through windows, vents, chimneys and gaps. Ventilation driven by wind and temperature differences, usually through windows, vents, chimneys and gaps.In more detailUses pressure differences caused by wind and temperature to move air through designed openings. Rates vary with weather and opening positions. It should not be confused with uncontrolled leakage through defects in the building.A practical exampleOpenable windows can provide rapid airing, while trickle vents support background air supply.Related termsThese are connected ideas, rather than always exact synonyms.Background VentilationAir Tightness\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Natural Ventilation<\/span><span class=\"mwh-entry-short\">Ventilation driven by wind and temperature differences, usually through windows, vents, chimneys and gaps.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Ventilation driven by wind and temperature differences, usually through windows, vents, chimneys and gaps.<\/p><h3>In more detail<\/h3><p>Uses pressure differences caused by wind and temperature to move air through designed openings. Rates vary with weather and opening positions. It should not be confused with uncontrolled leakage through defects in the building.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Openable windows can provide rapid airing, while trickle vents support background air supply.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-background-ventilation\" data-mwh-related=\"background-ventilation\">Background Ventilation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-tightness\" data-mwh-related=\"air-tightness\">Air Tightness<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-natural-ventilation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-non-traditional-construction\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"N\" data-categories=\"building-fabric-insulation\" data-search=\"Non-Traditional Construction   A broad description of construction systems such as some concrete-panel, steel-frame and system-built homes; identify the actual build-up before designing improvements. A broad description of construction systems such as some concrete-panel, steel-frame and system-built homes; identify the actual build-up before designing improvements.In more detailA broad description covering several construction systems rather than one uniform wall type. The actual frame, panels, cladding and alterations need identifying. Retrofit details suitable for masonry may not suit these structures.A practical exampleA steel-framed house may need checks for corrosion and condensation risk before insulation is designed.Related termsThese are connected ideas, rather than always exact synonyms.Timber FrameRetrofit Assessment\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Non-Traditional Construction<\/span><span class=\"mwh-entry-short\">A broad description of construction systems such as some concrete-panel, steel-frame and system-built homes; identify the actual build-up before designing improvements.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A broad description of construction systems such as some concrete-panel, steel-frame and system-built homes; identify the actual build-up before designing improvements.<\/p><h3>In more detail<\/h3><p>A broad description covering several construction systems rather than one uniform wall type. The actual frame, panels, cladding and alterations need identifying. Retrofit details suitable for masonry may not suit these structures.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A steel-framed house may need checks for corrosion and condensation risk before insulation is designed.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-timber-frame\" data-mwh-related=\"timber-frame\">Timber Frame<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-assessment\" data-mwh-related=\"retrofit-assessment\">Retrofit Assessment<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-non-traditional-construction\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"O\" aria-labelledby=\"mwh-letter-O\"><h2 id=\"mwh-letter-O\" class=\"mwh-dictionary-letter\">O<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-oil-boiler\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"O\" data-categories=\"heating-hot-water\" data-search=\"Oil Boiler   A boiler that burns heating oil to provide heating and hot water, common in some off-gas properties. A boiler that burns heating oil to provide heating and hot water, common in some off-gas properties.In more detailBurns stored heating oil, so a suitable tank and delivery access are needed as well as the boiler and flue. System maintenance and fuel storage condition matter. Competent advice is needed before altering appliances or storage arrangements.A practical exampleA rural home may have an external oil tank supplying a boiler in a utility room.Related termsThese are connected ideas, rather than always exact synonyms.BoilerFlue\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Oil Boiler<\/span><span class=\"mwh-entry-short\">A boiler that burns heating oil to provide heating and hot water, common in some off-gas properties.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A boiler that burns heating oil to provide heating and hot water, common in some off-gas properties.<\/p><h3>In more detail<\/h3><p>Burns stored heating oil, so a suitable tank and delivery access are needed as well as the boiler and flue. System maintenance and fuel storage condition matter. Competent advice is needed before altering appliances or storage arrangements.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A rural home may have an external oil tank supplying a boiler in a utility room.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-boiler\" data-mwh-related=\"boiler\">Boiler<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flue\" data-mwh-related=\"flue\">Flue<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-oil-boiler\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-opentherm\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"O\" data-categories=\"controls\" data-search=\"OpenTherm   A communication system that allows compatible boilers and controls to modulate heating output more efficiently. A communication system that allows compatible boilers and controls to modulate heating output more efficiently.In more detailA communications protocol used by some boilers and controls. Compatibility and supported functions vary. It can enable more responsive temperature control, but simply connecting an OpenTherm-labelled product does not guarantee correct commissioning or savings.A practical exampleA compatible controller can request a lower boiler water temperature as room demand falls.Related termsThese are connected ideas, rather than always exact synonyms.Compensation ControlsCommissioning\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">OpenTherm<\/span><span class=\"mwh-entry-short\">A communication system that allows compatible boilers and controls to modulate heating output more efficiently.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A communication system that allows compatible boilers and controls to modulate heating output more efficiently.<\/p><h3>In more detail<\/h3><p>A communications protocol used by some boilers and controls. Compatibility and supported functions vary. It can enable more responsive temperature control, but simply connecting an OpenTherm-labelled product does not guarantee correct commissioning or savings.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A compatible controller can request a lower boiler water temperature as room demand falls.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-compensation-controls\" data-mwh-related=\"compensation-controls\">Compensation Controls<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-commissioning\" data-mwh-related=\"commissioning\">Commissioning<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-opentherm\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-overheating\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"O\" data-categories=\"ventilation-air-quality\" data-search=\"Overheating   When a home becomes uncomfortably hot, often due to solar gains, poor ventilation, insufficient shading or high internal heat gains. When a home becomes uncomfortably hot, often due to solar gains, poor ventilation, insufficient shading or high internal heat gains.In more detailDepends on temperatures, duration and the needs of occupants, rather than one hot afternoon alone. Solar gains, internal gains, heat storage, ventilation and shading interact. Adding insulation should be considered alongside summer comfort.A practical exampleAn unshaded west-facing room can become too warm in late afternoon despite low heating demand.Related termsThese are connected ideas, rather than always exact synonyms.Solar GainThermal Mass\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Overheating<\/span><span class=\"mwh-entry-short\">When a home becomes uncomfortably hot, often due to solar gains, poor ventilation, insufficient shading or high internal heat gains.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">When a home becomes uncomfortably hot, often due to solar gains, poor ventilation, insufficient shading or high internal heat gains.<\/p><h3>In more detail<\/h3><p>Depends on temperatures, duration and the needs of occupants, rather than one hot afternoon alone. Solar gains, internal gains, heat storage, ventilation and shading interact. Adding insulation should be considered alongside summer comfort.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An unshaded west-facing room can become too warm in late afternoon despite low heating demand.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solar-gain\" data-mwh-related=\"solar-gain\">Solar Gain<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-mass\" data-mwh-related=\"thermal-mass\">Thermal Mass<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-overheating\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"P\" aria-labelledby=\"mwh-letter-P\"><h2 id=\"mwh-letter-P\" class=\"mwh-dictionary-letter\">P<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-party-wall\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"P\" data-categories=\"ventilation-air-quality\" data-search=\"Party Wall   A wall shared between two properties. A wall shared between two properties. It may need consideration during insulation, airtightness or ventilation works.In more detailSeparates adjoining properties or units. Its construction and any cavity can affect sound, fire separation and heat loss. Work must respect the relevant structural and legal requirements; it is not simply another external wall.A practical exampleAn open party-wall cavity can create a heat-loss bypass that differs from heat transfer through an outside wall.Related termsThese are connected ideas, rather than always exact synonyms.Thermal EnvelopeRetrofit Design\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Party Wall<\/span><span class=\"mwh-entry-short\">A wall shared between two properties.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A wall shared between two properties. It may need consideration during insulation, airtightness or ventilation works.<\/p><h3>In more detail<\/h3><p>Separates adjoining properties or units. Its construction and any cavity can affect sound, fire separation and heat loss. Work must respect the relevant structural and legal requirements; it is not simply another external wall.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An open party-wall cavity can create a heat-loss bypass that differs from heat transfer through an outside wall.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-envelope\" data-mwh-related=\"thermal-envelope\">Thermal Envelope<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-design\" data-mwh-related=\"retrofit-design\">Retrofit Design<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-party-wall\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-pas-2030\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"P\" data-categories=\"retrofit-standards\" data-search=\"PAS 2030   A standard covering the installation of energy-efficiency measures in existing buildings. A standard covering the installation of energy-efficiency measures in existing buildings.In more detailSets installation requirements for specified energy-efficiency measures in existing dwellings. It works alongside the wider retrofit process in PAS 2035. Ask which edition and certification requirements apply to the project rather than assuming a logo covers all work.A practical exampleAn installer records evidence that an insulation measure meets the applicable installation specification.Related termsThese are connected ideas, rather than always exact synonyms.PAS 2035Retrofit InstallerFurther reading: BSI: PAS 2035\/2030. Check current guidance for schemes and standards.\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">PAS 2030<\/span><span class=\"mwh-entry-short\">A standard covering the installation of energy-efficiency measures in existing buildings.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A standard covering the installation of energy-efficiency measures in existing buildings.<\/p><h3>In more detail<\/h3><p>Sets installation requirements for specified energy-efficiency measures in existing dwellings. It works alongside the wider retrofit process in PAS 2035. Ask which edition and certification requirements apply to the project rather than assuming a logo covers all work.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An installer records evidence that an insulation measure meets the applicable installation specification.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-pas-2035\" data-mwh-related=\"pas-2035\">PAS 2035<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-installer\" data-mwh-related=\"retrofit-installer\">Retrofit Installer<\/a><\/div><\/nav><p class=\"mwh-entry-source\">Further reading: <a href=\"https:\/\/knowledge.bsigroup.com\/products\/retrofitting-dwellings-for-improved-energy-efficiency-specification-and-guidance-4\">BSI: PAS 2035\/2030<\/a>. Check current guidance for schemes and standards.<\/p><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-pas-2030\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-pas-2035\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"P\" data-categories=\"ventilation-air-quality\" data-search=\"PAS 2035   The UK retrofit standard for assessing, designing and managing domestic retrofit projects using a whole-house approach. The UK retrofit standard for assessing, designing and managing domestic retrofit projects using a whole-house approach.In more detailSets out a coordinated whole-dwelling retrofit process, covering assessment, design, installation oversight and evaluation. It is more than a product specification. The required roles and evidence depend on the applicable standard and project arrangements.A practical exampleA retrofit coordinator considers how insulation and ventilation measures interact across a project.Related termsThese are connected ideas, rather than always exact synonyms.Retrofit CoordinatorWhole-House ApproachFurther reading: BSI: PAS 2035\/2030. Check current guidance for schemes and standards.\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">PAS 2035<\/span><span class=\"mwh-entry-short\">The UK retrofit standard for assessing, designing and managing domestic retrofit projects using a whole-house approach.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The UK retrofit standard for assessing, designing and managing domestic retrofit projects using a whole-house approach.<\/p><h3>In more detail<\/h3><p>Sets out a coordinated whole-dwelling retrofit process, covering assessment, design, installation oversight and evaluation. It is more than a product specification. The required roles and evidence depend on the applicable standard and project arrangements.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A retrofit coordinator considers how insulation and ventilation measures interact across a project.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-coordinator\" data-mwh-related=\"retrofit-coordinator\">Retrofit Coordinator<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-whole-house-approach\" data-mwh-related=\"whole-house-approach\">Whole-House Approach<\/a><\/div><\/nav><p class=\"mwh-entry-source\">Further reading: <a href=\"https:\/\/knowledge.bsigroup.com\/products\/retrofitting-dwellings-for-improved-energy-efficiency-specification-and-guidance-4\">BSI: PAS 2035\/2030<\/a>. Check current guidance for schemes and standards.<\/p><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-pas-2035\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-peak-load\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"P\" data-categories=\"heating-hot-water\" data-search=\"Peak Load   The highest heating demand expected during very cold conditions. The highest heating demand expected during very cold conditions.In more detailThe highest power demand considered in a design, under stated conditions. Heating, hot water and electricity can have different peaks and may not all occur together. It should not be confused with annual energy consumption.A practical exampleA heating system is checked against a cold-weather load, not just a yearly bill average.Related termsThese are connected ideas, rather than always exact synonyms.Design Heat LossKilowatt\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Peak Load<\/span><span class=\"mwh-entry-short\">The highest heating demand expected during very cold conditions.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The highest heating demand expected during very cold conditions.<\/p><h3>In more detail<\/h3><p>The highest power demand considered in a design, under stated conditions. Heating, hot water and electricity can have different peaks and may not all occur together. It should not be confused with annual energy consumption.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A heating system is checked against a cold-weather load, not just a yearly bill average.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-design-heat-loss\" data-mwh-related=\"design-heat-loss\">Design Heat Loss<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-kilowatt\" data-mwh-related=\"kilowatt\">Kilowatt<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-peak-load\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-penetrating-damp\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"P\" data-categories=\"moisture-damp\" data-search=\"Penetrating Damp   Moisture entering through the building fabric, often due to defects such as failed pointing, cracked render, roof leaks or blocked gutters. Moisture entering through the building fabric, often due to defects such as failed pointing, cracked render, roof leaks or blocked gutters.In more detailWater enters through an exposed part of the building, often following rain. The visible patch may be away from the actual defect because water can travel. Inspect roof details, gutters, openings and wall condition before treating the inside finish.A practical exampleA leaking gutter wets a wall and a stain appears inside after heavy rain.Related termsThese are connected ideas, rather than always exact synonyms.DampWeatherproofing\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Penetrating Damp<\/span><span class=\"mwh-entry-short\">Moisture entering through the building fabric, often due to defects such as failed pointing, cracked render, roof leaks or blocked gutters.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Moisture entering through the building fabric, often due to defects such as failed pointing, cracked render, roof leaks or blocked gutters.<\/p><h3>In more detail<\/h3><p>Water enters through an exposed part of the building, often following rain. The visible patch may be away from the actual defect because water can travel. Inspect roof details, gutters, openings and wall condition before treating the inside finish.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A leaking gutter wets a wall and a stain appears inside after heavy rain.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-damp\" data-mwh-related=\"damp\">Damp<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-weatherproofing\" data-mwh-related=\"weatherproofing\">Weatherproofing<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-penetrating-damp\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-perimeter-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"P\" data-categories=\"building-fabric-insulation\" data-search=\"Perimeter Insulation   Insulation installed around floor edges or foundations to reduce heat loss at junctions. Insulation installed around floor edges or foundations to reduce heat loss at junctions.In more detailTargets heat flow around the floor edge and its junction with walls or foundations. It is only part of the floor&#039;s thermal performance. Detailing must also maintain moisture protection and suit the structure.A practical exampleEdge insulation can reduce a cold strip where an insulated floor meets an outside wall.Related termsThese are connected ideas, rather than always exact synonyms.JunctionSolid Floor Insulation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Perimeter Insulation<\/span><span class=\"mwh-entry-short\">Insulation installed around floor edges or foundations to reduce heat loss at junctions.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Insulation installed around floor edges or foundations to reduce heat loss at junctions.<\/p><h3>In more detail<\/h3><p>Targets heat flow around the floor edge and its junction with walls or foundations. It is only part of the floor&#039;s thermal performance. Detailing must also maintain moisture protection and suit the structure.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Edge insulation can reduce a cold strip where an insulated floor meets an outside wall.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-junction\" data-mwh-related=\"junction\">Junction<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solid-floor-insulation\" data-mwh-related=\"solid-floor-insulation\">Solid Floor Insulation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-perimeter-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-phenolic-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"P\" data-categories=\"building-fabric-insulation\" data-search=\"Phenolic Insulation   A rigid insulation board with good thermal performance for its thickness. A rigid insulation board with good thermal performance for its thickness.In more detailA type of rigid foam insulation, often selected where a relatively thin build-up is needed. Thermal conductivity is only one consideration: moisture, fire classification, facings and system compatibility must be checked from the product specification.A practical exampleA designer may compare phenolic and PIR boards where an internal lining has limited available thickness.Related termsThese are connected ideas, rather than always exact synonyms.PIR InsulationThermal Conductivity\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Phenolic Insulation<\/span><span class=\"mwh-entry-short\">A rigid insulation board with good thermal performance for its thickness.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A rigid insulation board with good thermal performance for its thickness.<\/p><h3>In more detail<\/h3><p>A type of rigid foam insulation, often selected where a relatively thin build-up is needed. Thermal conductivity is only one consideration: moisture, fire classification, facings and system compatibility must be checked from the product specification.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A designer may compare phenolic and PIR boards where an internal lining has limited available thickness.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-pir-insulation\" data-mwh-related=\"pir-insulation\">PIR Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-conductivity\" data-mwh-related=\"thermal-conductivity\">Thermal Conductivity<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-phenolic-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-photovoltaics\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"P\" data-categories=\"renewables-electricity\" data-search=\"Photovoltaics PV PV Solar panels that generate electricity from daylight. Solar panels that generate electricity from daylight.Also called: PVIn more detailThe process of converting light into electricity using semiconductor cells. PV systems differ from solar thermal systems, which heat water. Output varies with daylight, orientation, shading and equipment performance.A practical exampleRoof panels generate electricity during daylight, with output varying through the day and seasons.Related termsThese are connected ideas, rather than always exact synonyms.Solar PVSolar Thermal\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Photovoltaics <span class=\"mwh-entry-acronym\">PV<\/span><\/span><span class=\"mwh-entry-short\">Solar panels that generate electricity from daylight.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Solar panels that generate electricity from daylight.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> PV<\/p><h3>In more detail<\/h3><p>The process of converting light into electricity using semiconductor cells. PV systems differ from solar thermal systems, which heat water. Output varies with daylight, orientation, shading and equipment performance.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Roof panels generate electricity during daylight, with output varying through the day and seasons.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solar-pv\" data-mwh-related=\"solar-pv\">Solar PV<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solar-thermal\" data-mwh-related=\"solar-thermal\">Solar Thermal<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-photovoltaics\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-pir-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"P\" data-categories=\"building-fabric-insulation\" data-search=\"PIR Insulation   Polyisocyanurate insulation board. Polyisocyanurate insulation board. A rigid foam board commonly used in walls, floors and roofs.In more detailA rigid polyisocyanurate foam product commonly supplied as boards. Facings, joint treatment, gaps and fixing methods influence the complete construction. A board&#039;s advertised conductivity does not by itself establish the wall or roof U-value.A practical exampleBoard edges are detailed to avoid gaps that could bypass the insulation.Related termsThese are connected ideas, rather than always exact synonyms.Phenolic InsulationU-Value\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">PIR Insulation<\/span><span class=\"mwh-entry-short\">Polyisocyanurate insulation board.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Polyisocyanurate insulation board. A rigid foam board commonly used in walls, floors and roofs.<\/p><h3>In more detail<\/h3><p>A rigid polyisocyanurate foam product commonly supplied as boards. Facings, joint treatment, gaps and fixing methods influence the complete construction. A board&#039;s advertised conductivity does not by itself establish the wall or roof U-value.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Board edges are detailed to avoid gaps that could bypass the insulation.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-phenolic-insulation\" data-mwh-related=\"phenolic-insulation\">Phenolic Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-u-value\" data-mwh-related=\"u-value\">U-Value<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-pir-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-planning-permission\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"P\" data-categories=\"renewables-electricity\" data-search=\"Planning Permission   Formal consent that may be needed for some external changes, such as external wall insulation, solar panels in sensitive areas or alterations to listed buildings. Formal consent that may be needed for some external changes, such as external wall insulation, solar panels in sensitive areas or alterations to listed buildings.In more detailControls certain development and changes of use. Some work can fall within permitted development, but conditions, local restrictions and protected buildings can alter the position. Building-regulations approval and listed-building consent are separate questions.A practical exampleA homeowner checks local rules before installing external insulation on a street-facing elevation.Related termsThese are connected ideas, rather than always exact synonyms.Conservation AreaListed Building\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Planning Permission<\/span><span class=\"mwh-entry-short\">Formal consent that may be needed for some external changes, such as external wall insulation, solar panels in sensitive areas or alterations to listed buildings.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Formal consent that may be needed for some external changes, such as external wall insulation, solar panels in sensitive areas or alterations to listed buildings.<\/p><h3>In more detail<\/h3><p>Controls certain development and changes of use. Some work can fall within permitted development, but conditions, local restrictions and protected buildings can alter the position. Building-regulations approval and listed-building consent are separate questions.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A homeowner checks local rules before installing external insulation on a street-facing elevation.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-conservation-area\" data-mwh-related=\"conservation-area\">Conservation Area<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-listed-building\" data-mwh-related=\"listed-building\">Listed Building<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-planning-permission\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-pressure-relief-valve\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"P\" data-categories=\"heating-hot-water\" data-search=\"Pressure Relief Valve PRV PRV A safety valve that releases pressure if a heating or hot water system becomes over-pressurised. A safety valve that releases pressure if a heating or hot water system becomes over-pressurised.Also called: PRVIn more detailA safety device that discharges when pressure exceeds its set limit. A discharge can indicate a problem elsewhere in the system. It must not be blocked, capped or treated as a routine means of pressure control.A practical exampleWater repeatedly escaping through a discharge pipe prompts an installer to investigate pressure and expansion arrangements.Related termsThese are connected ideas, rather than always exact synonyms.Expansion VesselCommissioning\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Pressure Relief Valve <span class=\"mwh-entry-acronym\">PRV<\/span><\/span><span class=\"mwh-entry-short\">A safety valve that releases pressure if a heating or hot water system becomes over-pressurised.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A safety valve that releases pressure if a heating or hot water system becomes over-pressurised.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> PRV<\/p><h3>In more detail<\/h3><p>A safety device that discharges when pressure exceeds its set limit. A discharge can indicate a problem elsewhere in the system. It must not be blocked, capped or treated as a routine means of pressure control.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Water repeatedly escaping through a discharge pipe prompts an installer to investigate pressure and expansion arrangements.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-expansion-vessel\" data-mwh-related=\"expansion-vessel\">Expansion Vessel<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-commissioning\" data-mwh-related=\"commissioning\">Commissioning<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-pressure-relief-valve\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-primary-energy\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"P\" data-categories=\"energy-performance\" data-search=\"Primary Energy   Energy accounted for at source, including the upstream energy needed to produce and deliver the energy used in the home. Energy accounted for at source, including the upstream energy needed to produce and deliver the energy used in the home.In more detailAccounts for energy used upstream to produce and deliver the energy supplied to the building, using specified conversion factors. It differs from delivered energy shown on a meter. The calculation method and factors must be stated.A practical exampleTwo systems using the same metered electricity can be compared using a published primary-energy factor.Related termsThese are connected ideas, rather than always exact synonyms.Energy Performance CertificateEnergy Efficiency\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Primary Energy<\/span><span class=\"mwh-entry-short\">Energy accounted for at source, including the upstream energy needed to produce and deliver the energy used in the home.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Energy accounted for at source, including the upstream energy needed to produce and deliver the energy used in the home.<\/p><h3>In more detail<\/h3><p>Accounts for energy used upstream to produce and deliver the energy supplied to the building, using specified conversion factors. It differs from delivered energy shown on a meter. The calculation method and factors must be stated.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Two systems using the same metered electricity can be compared using a published primary-energy factor.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-energy-performance-certificate\" data-mwh-related=\"energy-performance-certificate\">Energy Performance Certificate<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-energy-efficiency\" data-mwh-related=\"energy-efficiency\">Energy Efficiency<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-primary-energy\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-psi-value\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"P\" data-categories=\"building-fabric-insulation\" data-search=\"Psi Value   A measure of heat loss at junctions between building elements, such as around windows or where walls meet floors. A measure of heat loss at junctions between building elements, such as around windows or where walls meet floors.In more detailQuantifies extra linear heat transfer at a junction, usually in W\/(m\u00b7K). It is used with junction length in heat-loss calculations. It differs from a U-value, which describes heat transfer through an area.A practical exampleA window-edge junction has a psi value and a length, both contributing to the calculated heat loss.Related termsThese are connected ideas, rather than always exact synonyms.Thermal BridgeU-Value\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Psi Value<\/span><span class=\"mwh-entry-short\">A measure of heat loss at junctions between building elements, such as around windows or where walls meet floors.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A measure of heat loss at junctions between building elements, such as around windows or where walls meet floors.<\/p><h3>In more detail<\/h3><p>Quantifies extra linear heat transfer at a junction, usually in W\/(m\u00b7K). It is used with junction length in heat-loss calculations. It differs from a U-value, which describes heat transfer through an area.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A window-edge junction has a psi value and a length, both contributing to the calculated heat loss.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-bridge\" data-mwh-related=\"thermal-bridge\">Thermal Bridge<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-u-value\" data-mwh-related=\"u-value\">U-Value<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-psi-value\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"Q\" aria-labelledby=\"mwh-letter-Q\"><h2 id=\"mwh-letter-Q\" class=\"mwh-dictionary-letter\">Q<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-quality-assurance\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"Q\" data-categories=\"retrofit-standards\" data-search=\"Quality Assurance QA QA Checks carried out to make sure retrofit work has been assessed, designed, installed and recorded correctly. Checks carried out to make sure retrofit work has been assessed, designed, installed and recorded correctly.Also called: QAIn more detailUses planned checks, evidence and corrective action throughout a project. A final photograph alone may not show hidden defects. Useful assurance includes appropriate inspections before work is covered and records of commissioning and handover.A practical exampleAn insulation inspection before plasterboard goes on can reveal gaps that would later be concealed.Related termsThese are connected ideas, rather than always exact synonyms.CommissioningSpecification\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Quality Assurance <span class=\"mwh-entry-acronym\">QA<\/span><\/span><span class=\"mwh-entry-short\">Checks carried out to make sure retrofit work has been assessed, designed, installed and recorded correctly.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Checks carried out to make sure retrofit work has been assessed, designed, installed and recorded correctly.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> QA<\/p><h3>In more detail<\/h3><p>Uses planned checks, evidence and corrective action throughout a project. A final photograph alone may not show hidden defects. Useful assurance includes appropriate inspections before work is covered and records of commissioning and handover.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An insulation inspection before plasterboard goes on can reveal gaps that would later be concealed.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-commissioning\" data-mwh-related=\"commissioning\">Commissioning<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-specification\" data-mwh-related=\"specification\">Specification<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-quality-assurance\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"R\" aria-labelledby=\"mwh-letter-R\"><h2 id=\"mwh-letter-R\" class=\"mwh-dictionary-letter\">R<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-r-value\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"building-fabric-insulation\" data-search=\"R-Value   A measure of thermal resistance. A measure of thermal resistance. Higher R-values mean better resistance to heat flow.In more detailThermal resistance depends on material thickness divided by thermal conductivity. Higher resistance means less heat flow through that layer. It does not describe a whole construction unless all relevant layers and effects are included.A practical exampleDoubling the thickness of the same insulation approximately doubles that layer&#039;s thermal resistance.Related termsThese are connected ideas, rather than always exact synonyms.Lambda ValueU-Value\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">R-Value<\/span><span class=\"mwh-entry-short\">A measure of thermal resistance.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A measure of thermal resistance. Higher R-values mean better resistance to heat flow.<\/p><h3>In more detail<\/h3><p>Thermal resistance depends on material thickness divided by thermal conductivity. Higher resistance means less heat flow through that layer. It does not describe a whole construction unless all relevant layers and effects are included.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Doubling the thickness of the same insulation approximately doubles that layer&#039;s thermal resistance.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-lambda-value\" data-mwh-related=\"lambda-value\">Lambda Value<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-u-value\" data-mwh-related=\"u-value\">U-Value<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-r-value\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-radiator\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"heating-hot-water\" data-search=\"Radiator   A heat emitter that transfers heat from hot water into a room. A heat emitter that transfers heat from hot water into a room.In more detailTransfers heat to a room through both convection and radiation. Its output depends strongly on the temperature difference between the water and room air. Catalogue ratings should be adjusted to the proposed system conditions.A practical exampleA radiator rated at boiler temperatures may provide much less heat at heat-pump temperatures.Related termsThese are connected ideas, rather than always exact synonyms.Emitter SizingFlow Temperature\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Radiator<\/span><span class=\"mwh-entry-short\">A heat emitter that transfers heat from hot water into a room.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A heat emitter that transfers heat from hot water into a room.<\/p><h3>In more detail<\/h3><p>Transfers heat to a room through both convection and radiation. Its output depends strongly on the temperature difference between the water and room air. Catalogue ratings should be adjusted to the proposed system conditions.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A radiator rated at boiler temperatures may provide much less heat at heat-pump temperatures.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-emitter-sizing\" data-mwh-related=\"emitter-sizing\">Emitter Sizing<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flow-temperature\" data-mwh-related=\"flow-temperature\">Flow Temperature<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-radiator\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-rdsap\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"retrofit-standards\" data-search=\"RdSAP   Reduced Data Standard Assessment Procedure. Reduced Data Standard Assessment Procedure. The method used to assess the energy performance of existing UK homes for EPCs.In more detailUses a site survey and prescribed conventions to assess existing dwellings where full construction data is unavailable. Some inputs may be assumed under evidence rules. The resulting EPC is a standard comparison, not a forecast of a particular household&#039;s bill.A practical exampleAcceptable evidence of concealed insulation may change how an assessor records a wall or roof.Related termsThese are connected ideas, rather than always exact synonyms.SAPEnergy Performance CertificateFurther reading: Government: SAP and RdSAP. Check current guidance for schemes and standards.\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">RdSAP<\/span><span class=\"mwh-entry-short\">Reduced Data Standard Assessment Procedure.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Reduced Data Standard Assessment Procedure. The method used to assess the energy performance of existing UK homes for EPCs.<\/p><h3>In more detail<\/h3><p>Uses a site survey and prescribed conventions to assess existing dwellings where full construction data is unavailable. Some inputs may be assumed under evidence rules. The resulting EPC is a standard comparison, not a forecast of a particular household&#039;s bill.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Acceptable evidence of concealed insulation may change how an assessor records a wall or roof.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-sap\" data-mwh-related=\"sap\">SAP<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-energy-performance-certificate\" data-mwh-related=\"energy-performance-certificate\">Energy Performance Certificate<\/a><\/div><\/nav><p class=\"mwh-entry-source\">Further reading: <a href=\"https:\/\/www.gov.uk\/guidance\/standard-assessment-procedure\">Government: SAP and RdSAP<\/a>. Check current guidance for schemes and standards.<\/p><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-rdsap\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-refrigerant\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"heating-hot-water\" data-search=\"Refrigerant   The working fluid inside a heat pump or refrigeration system. The working fluid inside a heat pump or refrigeration system. It absorbs and releases heat as it changes pressure and state.In more detailA working fluid that absorbs and releases heat as pressure and state change in a refrigeration cycle. It is normally separate from the radiator water. Refrigerant type affects equipment design, safety arrangements and environmental considerations.A practical exampleHeat passes from refrigerant to heating water through a heat exchanger.Related termsThese are connected ideas, rather than always exact synonyms.Refrigeration CycleF-Gas\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Refrigerant<\/span><span class=\"mwh-entry-short\">The working fluid inside a heat pump or refrigeration system.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The working fluid inside a heat pump or refrigeration system. It absorbs and releases heat as it changes pressure and state.<\/p><h3>In more detail<\/h3><p>A working fluid that absorbs and releases heat as pressure and state change in a refrigeration cycle. It is normally separate from the radiator water. Refrigerant type affects equipment design, safety arrangements and environmental considerations.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Heat passes from refrigerant to heating water through a heat exchanger.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-refrigeration-cycle\" data-mwh-related=\"refrigeration-cycle\">Refrigeration Cycle<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-f-gas\" data-mwh-related=\"f-gas\">F-Gas<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-refrigerant\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-refrigeration-cycle\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"moisture-damp\" data-search=\"Refrigeration Cycle   The process used by heat pumps, fridges and air conditioners to move heat. The process used by heat pumps, fridges and air conditioners to move heat. The main stages are compression, condensation, expansion and evaporation.In more detailMoves heat through compression, heat release, expansion and heat absorption. A heat pump uses the useful heat released on the warm side. Individual components operate together, so faults cannot reliably be diagnosed from one temperature reading.A practical exampleA fridge cools its interior while releasing heat into the room behind it.Related termsThese are connected ideas, rather than always exact synonyms.CondenserExpansion Valve\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Refrigeration Cycle<\/span><span class=\"mwh-entry-short\">The process used by heat pumps, fridges and air conditioners to move heat.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The process used by heat pumps, fridges and air conditioners to move heat. The main stages are compression, condensation, expansion and evaporation.<\/p><h3>In more detail<\/h3><p>Moves heat through compression, heat release, expansion and heat absorption. A heat pump uses the useful heat released on the warm side. Individual components operate together, so faults cannot reliably be diagnosed from one temperature reading.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A fridge cools its interior while releasing heat into the room behind it.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-condenser\" data-mwh-related=\"condenser\">Condenser<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-expansion-valve\" data-mwh-related=\"expansion-valve\">Expansion Valve<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-refrigeration-cycle\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-relative-humidity\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"moisture-damp\" data-search=\"Relative Humidity RH RH The amount of water vapour present compared with saturation at the same temperature, expressed as a percentage. The amount of water vapour present compared with saturation at the same temperature, expressed as a percentage.Also called: RHIn more detailThe ratio of actual water-vapour pressure to saturation pressure at the same temperature, expressed as a percentage. Cooling air without removing moisture raises its relative humidity. A room reading does not reveal moisture conditions inside a wall.A practical exampleA cold corner can have a high local relative humidity even when a room-centre monitor looks acceptable.Related termsThese are connected ideas, rather than always exact synonyms.Dew PointCondensation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Relative Humidity <span class=\"mwh-entry-acronym\">RH<\/span><\/span><span class=\"mwh-entry-short\">The amount of water vapour present compared with saturation at the same temperature, expressed as a percentage.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The amount of water vapour present compared with saturation at the same temperature, expressed as a percentage.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> RH<\/p><h3>In more detail<\/h3><p>The ratio of actual water-vapour pressure to saturation pressure at the same temperature, expressed as a percentage. Cooling air without removing moisture raises its relative humidity. A room reading does not reveal moisture conditions inside a wall.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A cold corner can have a high local relative humidity even when a room-centre monitor looks acceptable.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-dew-point\" data-mwh-related=\"dew-point\">Dew Point<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-condensation\" data-mwh-related=\"condensation\">Condensation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-relative-humidity\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-render\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"building-fabric-insulation\" data-search=\"Render   An external finish applied to walls. An external finish applied to walls. It may be used as part of an external wall insulation system.In more detailA protective or decorative coating applied to an outside wall or insulation system. The correct mix, reinforcement and details depend on the substrate. Cracking, poor junctions or unsuitable coatings can allow rain in or impede drying.A practical exampleA crack below a sill may admit rain behind an otherwise sound-looking finish.Related termsThese are connected ideas, rather than always exact synonyms.WeatherproofingExternal Wall Insulation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Render<\/span><span class=\"mwh-entry-short\">An external finish applied to walls.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">An external finish applied to walls. It may be used as part of an external wall insulation system.<\/p><h3>In more detail<\/h3><p>A protective or decorative coating applied to an outside wall or insulation system. The correct mix, reinforcement and details depend on the substrate. Cracking, poor junctions or unsuitable coatings can allow rain in or impede drying.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A crack below a sill may admit rain behind an otherwise sound-looking finish.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-weatherproofing\" data-mwh-related=\"weatherproofing\">Weatherproofing<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-external-wall-insulation\" data-mwh-related=\"external-wall-insulation\">External Wall Insulation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-render\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-renewable-energy\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"renewables-electricity\" data-search=\"Renewable Energy   Energy from sources that naturally replenish, such as sunlight, wind, water and ambient heat. Energy from sources that naturally replenish, such as sunlight, wind, water and ambient heat.In more detailComes from sources replenished by natural processes. It does not mean every installation has zero environmental impact. Equipment manufacture, operation, fuel supply and the energy system still matter when comparing options.A practical exampleSolar panels generate renewable electricity but need suitable roof space and electrical design.Related termsThese are connected ideas, rather than always exact synonyms.Solar PVLow Carbon Heating\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Renewable Energy<\/span><span class=\"mwh-entry-short\">Energy from sources that naturally replenish, such as sunlight, wind, water and ambient heat.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Energy from sources that naturally replenish, such as sunlight, wind, water and ambient heat.<\/p><h3>In more detail<\/h3><p>Comes from sources replenished by natural processes. It does not mean every installation has zero environmental impact. Equipment manufacture, operation, fuel supply and the energy system still matter when comparing options.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Solar panels generate renewable electricity but need suitable roof space and electrical design.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solar-pv\" data-mwh-related=\"solar-pv\">Solar PV<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-low-carbon-heating\" data-mwh-related=\"low-carbon-heating\">Low Carbon Heating<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-renewable-energy\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-retrofit\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"retrofit-standards\" data-search=\"Retrofit   Improving an existing building to make it more energy efficient, comfortable, healthy and lower carbon. Improving an existing building to make it more energy efficient, comfortable, healthy and lower carbon.In more detailImproves an existing building rather than constructing a new one. Successful work balances energy, comfort, health, moisture and durability. A coordinated sequence avoids one improvement making a later measure harder or causing unintended problems.A practical examplePlanning ventilation alongside new windows can avoid reducing fresh air when draughts are sealed.Related termsThese are connected ideas, rather than always exact synonyms.Whole-House ApproachRetrofit Plan\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Retrofit<\/span><span class=\"mwh-entry-short\">Improving an existing building to make it more energy efficient, comfortable, healthy and lower carbon.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Improving an existing building to make it more energy efficient, comfortable, healthy and lower carbon.<\/p><h3>In more detail<\/h3><p>Improves an existing building rather than constructing a new one. Successful work balances energy, comfort, health, moisture and durability. A coordinated sequence avoids one improvement making a later measure harder or causing unintended problems.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Planning ventilation alongside new windows can avoid reducing fresh air when draughts are sealed.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-whole-house-approach\" data-mwh-related=\"whole-house-approach\">Whole-House Approach<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-plan\" data-mwh-related=\"retrofit-plan\">Retrofit Plan<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-retrofit-assessment\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"ventilation-air-quality\" data-search=\"Retrofit Assessment   A property assessment that looks at the building condition, occupancy, energy use, ventilation, heritage issues and suitability for improvement measures. A property assessment that looks at the building condition, occupancy, energy use, ventilation, heritage issues and suitability for improvement measures.In more detailCollects information needed to plan improvements, including condition, construction, occupancy and ventilation. It should identify uncertainties and further investigations. It is broader than simply listing the EPC&#039;s recommendations or measuring room sizes.A practical exampleSigns of damp may trigger additional investigation before wall insulation is proposed.Related termsThese are connected ideas, rather than always exact synonyms.AssessmentRetrofit Assessor\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Retrofit Assessment<\/span><span class=\"mwh-entry-short\">A property assessment that looks at the building condition, occupancy, energy use, ventilation, heritage issues and suitability for improvement measures.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A property assessment that looks at the building condition, occupancy, energy use, ventilation, heritage issues and suitability for improvement measures.<\/p><h3>In more detail<\/h3><p>Collects information needed to plan improvements, including condition, construction, occupancy and ventilation. It should identify uncertainties and further investigations. It is broader than simply listing the EPC&#039;s recommendations or measuring room sizes.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Signs of damp may trigger additional investigation before wall insulation is proposed.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-assessment\" data-mwh-related=\"assessment\">Assessment<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-assessor\" data-mwh-related=\"retrofit-assessor\">Retrofit Assessor<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-assessment\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-retrofit-assessor\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"retrofit-standards\" data-search=\"Retrofit Assessor   A qualified person who gathers the property information needed for a retrofit project. A qualified person who gathers the property information needed for a retrofit project.In more detailSurveys and records the information used by the wider retrofit team. The assessor&#039;s scope and competence should match the building. Gathering information does not make the assessor the designer or coordinator of every measure.A practical exampleThe assessor records an existing ventilation system and flags defects for the project team.Related termsThese are connected ideas, rather than always exact synonyms.Retrofit AssessmentRetrofit Coordinator\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Retrofit Assessor<\/span><span class=\"mwh-entry-short\">A qualified person who gathers the property information needed for a retrofit project.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A qualified person who gathers the property information needed for a retrofit project.<\/p><h3>In more detail<\/h3><p>Surveys and records the information used by the wider retrofit team. The assessor&#039;s scope and competence should match the building. Gathering information does not make the assessor the designer or coordinator of every measure.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>The assessor records an existing ventilation system and flags defects for the project team.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-assessment\" data-mwh-related=\"retrofit-assessment\">Retrofit Assessment<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-coordinator\" data-mwh-related=\"retrofit-coordinator\">Retrofit Coordinator<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-assessor\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-retrofit-coordinator\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"retrofit-standards\" data-search=\"Retrofit Coordinator   A qualified person responsible for overseeing the retrofit process under PAS 2035, including risk management and coordination. A qualified person responsible for overseeing the retrofit process under PAS 2035, including risk management and coordination.In more detailCoordinates the retrofit process and relevant risk management under the applicable project framework. The role brings assessments, designs, installation information and evaluation together. It does not remove the responsibilities of designers or installers.A practical exampleThe coordinator checks that a ventilation upgrade is considered alongside planned insulation.Related termsThese are connected ideas, rather than always exact synonyms.PAS 2035Retrofit Design\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Retrofit Coordinator<\/span><span class=\"mwh-entry-short\">A qualified person responsible for overseeing the retrofit process under PAS 2035, including risk management and coordination.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A qualified person responsible for overseeing the retrofit process under PAS 2035, including risk management and coordination.<\/p><h3>In more detail<\/h3><p>Coordinates the retrofit process and relevant risk management under the applicable project framework. The role brings assessments, designs, installation information and evaluation together. It does not remove the responsibilities of designers or installers.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>The coordinator checks that a ventilation upgrade is considered alongside planned insulation.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-pas-2035\" data-mwh-related=\"pas-2035\">PAS 2035<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-design\" data-mwh-related=\"retrofit-design\">Retrofit Design<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-coordinator\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-retrofit-design\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"ventilation-air-quality\" data-search=\"Retrofit Design   The technical design of energy-efficiency measures, including specifications, drawings, moisture risk and ventilation requirements. The technical design of energy-efficiency measures, including specifications, drawings, moisture risk and ventilation requirements.In more detailTurns survey findings and objectives into construction and system details. It should specify interfaces, moisture control, ventilation and performance requirements. A sales quotation naming a product is not necessarily a complete retrofit design.A practical exampleA design shows how wall insulation meets roof edges, window sills and ground level.Related termsThese are connected ideas, rather than always exact synonyms.SpecificationJunction\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Retrofit Design<\/span><span class=\"mwh-entry-short\">The technical design of energy-efficiency measures, including specifications, drawings, moisture risk and ventilation requirements.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The technical design of energy-efficiency measures, including specifications, drawings, moisture risk and ventilation requirements.<\/p><h3>In more detail<\/h3><p>Turns survey findings and objectives into construction and system details. It should specify interfaces, moisture control, ventilation and performance requirements. A sales quotation naming a product is not necessarily a complete retrofit design.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A design shows how wall insulation meets roof edges, window sills and ground level.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-specification\" data-mwh-related=\"specification\">Specification<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-junction\" data-mwh-related=\"junction\">Junction<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-design\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-retrofit-installer\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"ventilation-air-quality\" data-search=\"Retrofit Installer   A contractor who installs energy-efficiency measures such as insulation, heating, ventilation or renewables. A contractor who installs energy-efficiency measures such as insulation, heating, ventilation or renewables.In more detailCarries out the specified work using suitable competence and project procedures. Product knowledge alone is not enough where building defects or complex interfaces are involved. Evidence, commissioning and a clear handover are part of good delivery.A practical exampleAn installer records hidden insulation details before covering them with the final finish.Related termsThese are connected ideas, rather than always exact synonyms.PAS 2030Quality Assurance\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Retrofit Installer<\/span><span class=\"mwh-entry-short\">A contractor who installs energy-efficiency measures such as insulation, heating, ventilation or renewables.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A contractor who installs energy-efficiency measures such as insulation, heating, ventilation or renewables.<\/p><h3>In more detail<\/h3><p>Carries out the specified work using suitable competence and project procedures. Product knowledge alone is not enough where building defects or complex interfaces are involved. Evidence, commissioning and a clear handover are part of good delivery.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An installer records hidden insulation details before covering them with the final finish.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-pas-2030\" data-mwh-related=\"pas-2030\">PAS 2030<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-quality-assurance\" data-mwh-related=\"quality-assurance\">Quality Assurance<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-installer\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-retrofit-plan\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"ventilation-air-quality\" data-search=\"Retrofit Plan   A staged plan for improving a home over time, often following a whole-house approach. A staged plan for improving a home over time, often following a whole-house approach.In more detailSets out improvements and their sequence, including interactions and future work. It can be staged around budgets and maintenance opportunities. It should be based on the actual building, rather than a universal list of products.A practical exampleRoof repairs can be coordinated with insulation before the final heating system is sized.Related termsThese are connected ideas, rather than always exact synonyms.Whole-House Retrofit PlanFabric First\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Retrofit Plan<\/span><span class=\"mwh-entry-short\">A staged plan for improving a home over time, often following a whole-house approach.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A staged plan for improving a home over time, often following a whole-house approach.<\/p><h3>In more detail<\/h3><p>Sets out improvements and their sequence, including interactions and future work. It can be staged around budgets and maintenance opportunities. It should be based on the actual building, rather than a universal list of products.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Roof repairs can be coordinated with insulation before the final heating system is sized.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-whole-house-retrofit-plan\" data-mwh-related=\"whole-house-retrofit-plan\">Whole-House Retrofit Plan<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-fabric-first\" data-mwh-related=\"fabric-first\">Fabric First<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-plan\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-return-temperature\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"heating-hot-water\" data-search=\"Return Temperature   The temperature of water returning from radiators or underfloor heating back to the boiler or heat pump. The temperature of water returning from radiators or underfloor heating back to the boiler or heat pump.In more detailThe water temperature coming back from an emitter or circuit. The difference from flow temperature helps describe heat delivery and system operation. It should be interpreted with flow rate and the particular heat-source requirements.A practical exampleA boiler&#039;s ability to condense can be influenced by the returning water temperature.Related termsThese are connected ideas, rather than always exact synonyms.Flow TemperatureFlow Rate\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Return Temperature<\/span><span class=\"mwh-entry-short\">The temperature of water returning from radiators or underfloor heating back to the boiler or heat pump.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The temperature of water returning from radiators or underfloor heating back to the boiler or heat pump.<\/p><h3>In more detail<\/h3><p>The water temperature coming back from an emitter or circuit. The difference from flow temperature helps describe heat delivery and system operation. It should be interpreted with flow rate and the particular heat-source requirements.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A boiler&#039;s ability to condense can be influenced by the returning water temperature.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flow-temperature\" data-mwh-related=\"flow-temperature\">Flow Temperature<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flow-rate\" data-mwh-related=\"flow-rate\">Flow Rate<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-return-temperature\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-rising-damp\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"moisture-damp\" data-search=\"Rising Damp   Ground moisture drawn upwards through porous building materials. A low damp patch alone does not prove rising damp. Ground moisture drawn upwards through porous building materials. A low damp patch alone does not prove rising damp.In more detailDescribes liquid moisture moving upwards through porous materials in contact with the ground. It is often misdiagnosed. Ground levels, drainage, leaks, salts and other moisture routes need investigation before a remedial damp-proofing treatment is selected.A practical exampleA low damp patch is investigated rather than automatically treated with chemical injection. A leaking pipe might be the real source.Related termsThese are connected ideas, rather than always exact synonyms.Damp Proof CoursePenetrating Damp\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Rising Damp<\/span><span class=\"mwh-entry-short\">Ground moisture drawn upwards through porous building materials. A low damp patch alone does not prove rising damp.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Ground moisture drawn upwards through porous building materials. A low damp patch alone does not prove rising damp.<\/p><h3>In more detail<\/h3><p>Describes liquid moisture moving upwards through porous materials in contact with the ground. It is often misdiagnosed. Ground levels, drainage, leaks, salts and other moisture routes need investigation before a remedial damp-proofing treatment is selected.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A low damp patch is investigated rather than automatically treated with chemical injection. A leaking pipe might be the real source.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-damp-proof-course\" data-mwh-related=\"damp-proof-course\">Damp Proof Course<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-penetrating-damp\" data-mwh-related=\"penetrating-damp\">Penetrating Damp<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-rising-damp\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-room-by-room-heat-loss\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"R\" data-categories=\"ventilation-air-quality\" data-search=\"Room-by-Room Heat Loss   A detailed calculation of heat loss for each room, used to size radiators, underfloor heating and heat pumps. A detailed calculation of heat loss for each room, used to size radiators, underfloor heating and heat pumps.In more detailCalculates each room&#039;s design heating load using its size, surfaces, construction and ventilation assumptions. It helps distribute heat correctly rather than just estimating a total for the home. Survey assumptions and design temperatures should be documented.A practical exampleA room with two outside walls and large glazing may need more heat than a similar-sized internal room.Related termsThese are connected ideas, rather than always exact synonyms.Heat Loss CalculationEmitter Sizing\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Room-by-Room Heat Loss<\/span><span class=\"mwh-entry-short\">A detailed calculation of heat loss for each room, used to size radiators, underfloor heating and heat pumps.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A detailed calculation of heat loss for each room, used to size radiators, underfloor heating and heat pumps.<\/p><h3>In more detail<\/h3><p>Calculates each room&#039;s design heating load using its size, surfaces, construction and ventilation assumptions. It helps distribute heat correctly rather than just estimating a total for the home. Survey assumptions and design temperatures should be documented.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A room with two outside walls and large glazing may need more heat than a similar-sized internal room.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-loss-calculation\" data-mwh-related=\"heat-loss-calculation\">Heat Loss Calculation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-emitter-sizing\" data-mwh-related=\"emitter-sizing\">Emitter Sizing<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-room-by-room-heat-loss\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"S\" aria-labelledby=\"mwh-letter-S\"><h2 id=\"mwh-letter-S\" class=\"mwh-dictionary-letter\">S<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-sap\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"retrofit-standards\" data-search=\"SAP   Standard Assessment Procedure. Standard Assessment Procedure. The UK method for assessing the energy performance of new dwellings.In more detailThe Standard Assessment Procedure is a government methodology for modelling dwelling energy performance. It uses defined inputs and assumptions rather than actual bills. Full SAP is commonly used where detailed construction information is available; RdSAP adapts the approach for existing homes.A practical exampleA new dwelling&#039;s assessment uses its design specification, dimensions and systems.Related termsThese are connected ideas, rather than always exact synonyms.RdSAPEnergy Performance CertificateFurther reading: Government: SAP and RdSAP. Check current guidance for schemes and standards.\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">SAP<\/span><span class=\"mwh-entry-short\">Standard Assessment Procedure.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Standard Assessment Procedure. The UK method for assessing the energy performance of new dwellings.<\/p><h3>In more detail<\/h3><p>The Standard Assessment Procedure is a government methodology for modelling dwelling energy performance. It uses defined inputs and assumptions rather than actual bills. Full SAP is commonly used where detailed construction information is available; RdSAP adapts the approach for existing homes.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A new dwelling&#039;s assessment uses its design specification, dimensions and systems.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-rdsap\" data-mwh-related=\"rdsap\">RdSAP<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-energy-performance-certificate\" data-mwh-related=\"energy-performance-certificate\">Energy Performance Certificate<\/a><\/div><\/nav><p class=\"mwh-entry-source\">Further reading: <a href=\"https:\/\/www.gov.uk\/guidance\/standard-assessment-procedure\">Government: SAP and RdSAP<\/a>. Check current guidance for schemes and standards.<\/p><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-sap\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-seasonal-coefficient-of-performance\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"heating-hot-water\" data-search=\"Seasonal Coefficient of Performance SCOP SCOP A seasonal measure of heat pump efficiency over a period of heating operation. A seasonal measure of heat pump efficiency over a period of heating operation.Also called: SCOPIn more detailA standardised seasonal efficiency figure calculated under defined climate and operating conditions. It is useful for comparing products on a like-for-like basis, but is not a promise of the performance achieved in an individual home.A practical exampleCompare heat pumps at the same stated water-temperature and climate conditions.Related termsThese are connected ideas, rather than always exact synonyms.Coefficient of PerformanceSeasonal Performance Factor\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Seasonal Coefficient of Performance <span class=\"mwh-entry-acronym\">SCOP<\/span><\/span><span class=\"mwh-entry-short\">A seasonal measure of heat pump efficiency over a period of heating operation.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A seasonal measure of heat pump efficiency over a period of heating operation.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> SCOP<\/p><h3>In more detail<\/h3><p>A standardised seasonal efficiency figure calculated under defined climate and operating conditions. It is useful for comparing products on a like-for-like basis, but is not a promise of the performance achieved in an individual home.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Compare heat pumps at the same stated water-temperature and climate conditions.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-coefficient-of-performance\" data-mwh-related=\"coefficient-of-performance\">Coefficient of Performance<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-seasonal-performance-factor\" data-mwh-related=\"seasonal-performance-factor\">Seasonal Performance Factor<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-seasonal-coefficient-of-performance\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-seasonal-performance-factor\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"heating-hot-water\" data-search=\"Seasonal Performance Factor SPF SPF A measure of heat pump performance over time, comparing useful heat output to electricity input. A measure of heat pump performance over time, comparing useful heat output to electricity input.Also called: SPFIn more detailCompares useful heat supplied with electricity consumed over a stated period and measurement boundary. Ask whether pumps, immersion heating and other auxiliaries are included. Figures with different boundaries or weather conditions are not directly comparable.A practical exampleA year&#039;s monitored heating output is divided by the electricity used by the defined system.Related termsThese are connected ideas, rather than always exact synonyms.Seasonal Coefficient of PerformanceCoefficient of Performance\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Seasonal Performance Factor <span class=\"mwh-entry-acronym\">SPF<\/span><\/span><span class=\"mwh-entry-short\">A measure of heat pump performance over time, comparing useful heat output to electricity input.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A measure of heat pump performance over time, comparing useful heat output to electricity input.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> SPF<\/p><h3>In more detail<\/h3><p>Compares useful heat supplied with electricity consumed over a stated period and measurement boundary. Ask whether pumps, immersion heating and other auxiliaries are included. Figures with different boundaries or weather conditions are not directly comparable.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A year&#039;s monitored heating output is divided by the electricity used by the defined system.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-seasonal-coefficient-of-performance\" data-mwh-related=\"seasonal-coefficient-of-performance\">Seasonal Coefficient of Performance<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-coefficient-of-performance\" data-mwh-related=\"coefficient-of-performance\">Coefficient of Performance<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-seasonal-performance-factor\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-secondary-glazing\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"building-fabric-insulation\" data-search=\"Secondary Glazing   An additional pane or frame fitted inside an existing window to improve thermal performance, comfort and noise reduction. An additional pane or frame fitted inside an existing window to improve thermal performance, comfort and noise reduction.In more detailAdds a separate inner glazing layer while retaining the existing window. Performance depends on fit, seals, cavity and design. It can help where replacing original windows is unsuitable, but moisture and ventilation arrangements still need thought.A practical exampleAn internal secondary pane can reduce draughts behind a retained historic sash window.Related termsThese are connected ideas, rather than always exact synonyms.GlazingListed Building\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Secondary Glazing<\/span><span class=\"mwh-entry-short\">An additional pane or frame fitted inside an existing window to improve thermal performance, comfort and noise reduction.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">An additional pane or frame fitted inside an existing window to improve thermal performance, comfort and noise reduction.<\/p><h3>In more detail<\/h3><p>Adds a separate inner glazing layer while retaining the existing window. Performance depends on fit, seals, cavity and design. It can help where replacing original windows is unsuitable, but moisture and ventilation arrangements still need thought.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An internal secondary pane can reduce draughts behind a retained historic sash window.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-glazing\" data-mwh-related=\"glazing\">Glazing<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-listed-building\" data-mwh-related=\"listed-building\">Listed Building<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-secondary-glazing\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-service-penetration\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"building-fabric-insulation\" data-search=\"Service Penetration   A place where pipes, cables or ducts pass through the building fabric. A place where pipes, cables or ducts pass through the building fabric. Poorly sealed penetrations can cause draughts and heat loss.In more detailAn opening where a pipe, cable or duct passes through a building layer. It may need separate airtightness, fire, acoustic and weather seals. Filling a visible gap without understanding those requirements can be inappropriate.A practical exampleAn extractor duct passing through a wall needs a suitable seal and exterior termination.Related termsThese are connected ideas, rather than always exact synonyms.Air TightnessJunction\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Service Penetration<\/span><span class=\"mwh-entry-short\">A place where pipes, cables or ducts pass through the building fabric.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A place where pipes, cables or ducts pass through the building fabric. Poorly sealed penetrations can cause draughts and heat loss.<\/p><h3>In more detail<\/h3><p>An opening where a pipe, cable or duct passes through a building layer. It may need separate airtightness, fire, acoustic and weather seals. Filling a visible gap without understanding those requirements can be inappropriate.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An extractor duct passing through a wall needs a suitable seal and exterior termination.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-tightness\" data-mwh-related=\"air-tightness\">Air Tightness<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-junction\" data-mwh-related=\"junction\">Junction<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-service-penetration\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-smart-meter\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"energy-performance\" data-search=\"Smart Meter   A meter that records energy use and sends readings automatically to the supplier. A meter that records energy use and sends readings automatically to the supplier.In more detailRecords energy consumption and can send readings to the supplier using a communications system. An in-home display helps show usage but does not control every appliance. Tariffs and data arrangements should be checked with the supplier.A practical exampleThe display can show how electricity use rises when several appliances run together.Related termsThese are connected ideas, rather than always exact synonyms.Kilowatt HourEnergy Efficiency\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Smart Meter<\/span><span class=\"mwh-entry-short\">A meter that records energy use and sends readings automatically to the supplier.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A meter that records energy use and sends readings automatically to the supplier.<\/p><h3>In more detail<\/h3><p>Records energy consumption and can send readings to the supplier using a communications system. An in-home display helps show usage but does not control every appliance. Tariffs and data arrangements should be checked with the supplier.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>The display can show how electricity use rises when several appliances run together.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-kilowatt-hour\" data-mwh-related=\"kilowatt-hour\">Kilowatt Hour<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-energy-efficiency\" data-mwh-related=\"energy-efficiency\">Energy Efficiency<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-smart-meter\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-solar-gain\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"renewables-electricity\" data-search=\"Solar Gain   Heat gained from sunlight entering a building, especially through windows. Heat gained from sunlight entering a building, especially through windows.In more detailSunlight becomes useful heat when absorbed by the building or its contents. Window orientation, glass, shading and season affect the amount. Helpful winter gains can become unwanted summer heat, so design needs both considerations.A practical exampleA south-facing window can warm a room in winter but may benefit from summer shading.Related termsThese are connected ideas, rather than always exact synonyms.OverheatingGlazing\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Solar Gain<\/span><span class=\"mwh-entry-short\">Heat gained from sunlight entering a building, especially through windows.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Heat gained from sunlight entering a building, especially through windows.<\/p><h3>In more detail<\/h3><p>Sunlight becomes useful heat when absorbed by the building or its contents. Window orientation, glass, shading and season affect the amount. Helpful winter gains can become unwanted summer heat, so design needs both considerations.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A south-facing window can warm a room in winter but may benefit from summer shading.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-overheating\" data-mwh-related=\"overheating\">Overheating<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-glazing\" data-mwh-related=\"glazing\">Glazing<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solar-gain\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-solar-pv\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"renewables-electricity\" data-search=\"Solar PV   Solar photovoltaic panels that generate electricity. Solar photovoltaic panels that generate electricity.In more detailPhotovoltaic modules turn daylight into electricity, usually through an inverter supplying usable AC electricity. Generation varies with weather, orientation and shading. Panel peak capacity in kWp differs from energy generated over a year in kWh.A practical exampleA household uses some daytime generation immediately and exports or stores the remainder.Related termsThese are connected ideas, rather than always exact synonyms.PhotovoltaicsBattery Storage\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Solar PV<\/span><span class=\"mwh-entry-short\">Solar photovoltaic panels that generate electricity.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Solar photovoltaic panels that generate electricity.<\/p><h3>In more detail<\/h3><p>Photovoltaic modules turn daylight into electricity, usually through an inverter supplying usable AC electricity. Generation varies with weather, orientation and shading. Panel peak capacity in kWp differs from energy generated over a year in kWh.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A household uses some daytime generation immediately and exports or stores the remainder.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-photovoltaics\" data-mwh-related=\"photovoltaics\">Photovoltaics<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-battery-storage\" data-mwh-related=\"battery-storage\">Battery Storage<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solar-pv\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-solar-thermal\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"renewables-electricity\" data-search=\"Solar Thermal   Solar panels that use sunlight to heat water. Solar panels that use sunlight to heat water.In more detailUses collectors to transfer solar heat into a hot-water system, normally through a cylinder and heat exchanger. It produces heat rather than electricity. Design should consider storage, controls and backup water heating.A practical exampleSolar collectors can contribute to hot-water demand while another heat source covers periods of low sunshine.Related termsThese are connected ideas, rather than always exact synonyms.Solar PVHot Water Cylinder\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Solar Thermal<\/span><span class=\"mwh-entry-short\">Solar panels that use sunlight to heat water.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Solar panels that use sunlight to heat water.<\/p><h3>In more detail<\/h3><p>Uses collectors to transfer solar heat into a hot-water system, normally through a cylinder and heat exchanger. It produces heat rather than electricity. Design should consider storage, controls and backup water heating.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Solar collectors can contribute to hot-water demand while another heat source covers periods of low sunshine.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solar-pv\" data-mwh-related=\"solar-pv\">Solar PV<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-hot-water-cylinder\" data-mwh-related=\"hot-water-cylinder\">Hot Water Cylinder<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solar-thermal\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-solid-floor-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"building-fabric-insulation\" data-search=\"Solid Floor Insulation   Insulation added above or below a solid concrete floor. Insulation added above or below a solid concrete floor.In more detailMay be installed above an existing slab or as part of a rebuilt floor. Raising the floor affects doors, stairs and thresholds. Moisture protection, perimeter details and the load-bearing build-up need coordinated design.A practical exampleAdding insulation above a slab may require adjustments to door clearances and kitchen units.Related termsThese are connected ideas, rather than always exact synonyms.Floor InsulationPerimeter Insulation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Solid Floor Insulation<\/span><span class=\"mwh-entry-short\">Insulation added above or below a solid concrete floor.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Insulation added above or below a solid concrete floor.<\/p><h3>In more detail<\/h3><p>May be installed above an existing slab or as part of a rebuilt floor. Raising the floor affects doors, stairs and thresholds. Moisture protection, perimeter details and the load-bearing build-up need coordinated design.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Adding insulation above a slab may require adjustments to door clearances and kitchen units.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-floor-insulation\" data-mwh-related=\"floor-insulation\">Floor Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-perimeter-insulation\" data-mwh-related=\"perimeter-insulation\">Perimeter Insulation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solid-floor-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-solid-wall\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"building-fabric-insulation\" data-search=\"Solid Wall   A wall without a cavity, often found in older homes. A wall without a cavity, often found in older homes. Solid walls can be insulated internally or externally.In more detailHas no continuous cavity suitable for ordinary cavity-fill insulation. Brick, stone, earth and other constructions behave differently. Condition, rain exposure, finishes and drying ability must be considered before deciding on internal or external insulation.A practical exampleAn older stone wall may need a different moisture assessment from a solid brick wall.Related termsThese are connected ideas, rather than always exact synonyms.Internal Wall InsulationExternal Wall Insulation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Solid Wall<\/span><span class=\"mwh-entry-short\">A wall without a cavity, often found in older homes.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A wall without a cavity, often found in older homes. Solid walls can be insulated internally or externally.<\/p><h3>In more detail<\/h3><p>Has no continuous cavity suitable for ordinary cavity-fill insulation. Brick, stone, earth and other constructions behave differently. Condition, rain exposure, finishes and drying ability must be considered before deciding on internal or external insulation.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An older stone wall may need a different moisture assessment from a solid brick wall.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-internal-wall-insulation\" data-mwh-related=\"internal-wall-insulation\">Internal Wall Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-external-wall-insulation\" data-mwh-related=\"external-wall-insulation\">External Wall Insulation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solid-wall\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-space-heating\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"heating-hot-water\" data-search=\"Space Heating   Heating used to warm the rooms in a home. Heating used to warm the rooms in a home.In more detailHeat supplied to occupied rooms for comfort, separate from hot water used at taps. Its demand changes with weather and building performance. Separating the two helps explain bills and size or compare heating systems.A practical exampleA summer energy bill can still include hot-water energy even when room heating is off.Related termsThese are connected ideas, rather than always exact synonyms.Domestic Hot WaterHeat Demand\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Space Heating<\/span><span class=\"mwh-entry-short\">Heating used to warm the rooms in a home.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Heating used to warm the rooms in a home.<\/p><h3>In more detail<\/h3><p>Heat supplied to occupied rooms for comfort, separate from hot water used at taps. Its demand changes with weather and building performance. Separating the two helps explain bills and size or compare heating systems.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A summer energy bill can still include hot-water energy even when room heating is off.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-domestic-hot-water\" data-mwh-related=\"domestic-hot-water\">Domestic Hot Water<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-demand\" data-mwh-related=\"heat-demand\">Heat Demand<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-space-heating\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-specification\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"retrofit-standards\" data-search=\"Specification   The written technical detail describing how retrofit measures should be installed. The written technical detail describing how retrofit measures should be installed.In more detailSets out the required materials, workmanship, details and performance for the work. It should be specific enough to install and inspect against. A product brochure or short quotation does not describe every junction and interface.A practical exampleAn insulation specification identifies thickness, fixings, fire details and treatment around openings.Related termsThese are connected ideas, rather than always exact synonyms.Retrofit DesignQuality Assurance\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Specification<\/span><span class=\"mwh-entry-short\">The written technical detail describing how retrofit measures should be installed.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The written technical detail describing how retrofit measures should be installed.<\/p><h3>In more detail<\/h3><p>Sets out the required materials, workmanship, details and performance for the work. It should be specific enough to install and inspect against. A product brochure or short quotation does not describe every junction and interface.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An insulation specification identifies thickness, fixings, fire details and treatment around openings.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-design\" data-mwh-related=\"retrofit-design\">Retrofit Design<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-quality-assurance\" data-mwh-related=\"quality-assurance\">Quality Assurance<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-specification\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-split-system\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"\" data-search=\"Split System   A &quot;split&quot; system is divided into separate indoor and outdoor units. A &quot;split&quot; system is divided into separate indoor and outdoor units.In more detailSeparates heat-pump components between indoor and outdoor units, commonly with refrigerant connections between them in an air-to-water split arrangement. The exact configuration varies. Installation must follow the manufacturer&#039;s requirements and applicable competence rules.A practical exampleAn indoor hydrobox exchanges heat between refrigerant pipework and the heating-water circuit.Related termsThese are connected ideas, rather than always exact synonyms.MonoblocHydrobox\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Split System<\/span><span class=\"mwh-entry-short\">A &quot;split&quot; system is divided into separate indoor and outdoor units.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A &quot;split&quot; system is divided into separate indoor and outdoor units.<\/p><h3>In more detail<\/h3><p>Separates heat-pump components between indoor and outdoor units, commonly with refrigerant connections between them in an air-to-water split arrangement. The exact configuration varies. Installation must follow the manufacturer&#039;s requirements and applicable competence rules.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An indoor hydrobox exchanges heat between refrigerant pipework and the heating-water circuit.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-monobloc\" data-mwh-related=\"monobloc\">Monobloc<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-hydrobox\" data-mwh-related=\"hydrobox\">Hydrobox<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-split-system\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-suspended-timber-floor\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"ventilation-air-quality\" data-search=\"Suspended Timber Floor   A timber floor with a ventilated void underneath. A timber floor with a ventilated void underneath. It can often be insulated between the joists.In more detailFloorboards and joists sit above a void rather than directly on the ground. Moisture, timber condition and underfloor ventilation need assessment. Insulation should reduce heat loss without creating damp or blocking required air paths.A practical exampleAir bricks should continue ventilating the floor void after insulation is installed.Related termsThese are connected ideas, rather than always exact synonyms.Floor InsulationMoisture Balance\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Suspended Timber Floor<\/span><span class=\"mwh-entry-short\">A timber floor with a ventilated void underneath.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A timber floor with a ventilated void underneath. It can often be insulated between the joists.<\/p><h3>In more detail<\/h3><p>Floorboards and joists sit above a void rather than directly on the ground. Moisture, timber condition and underfloor ventilation need assessment. Insulation should reduce heat loss without creating damp or blocking required air paths.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Air bricks should continue ventilating the floor void after insulation is installed.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-floor-insulation\" data-mwh-related=\"floor-insulation\">Floor Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-moisture-balance\" data-mwh-related=\"moisture-balance\">Moisture Balance<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-suspended-timber-floor\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-system-boiler\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"S\" data-categories=\"heating-hot-water\" data-search=\"System Boiler   A boiler that works with a hot water cylinder but has many components built into the boiler unit. A boiler that works with a hot water cylinder but has many components built into the boiler unit.In more detailSupplies a wet heating system and usually a separate hot-water cylinder, with certain system components built into the appliance. The exact layout varies. Cylinder capacity and reheating performance remain important hot-water considerations.A practical exampleA family home can store hot water in a cylinder supplied by a system boiler.Related termsThese are connected ideas, rather than always exact synonyms.Combi BoilerHot Water Cylinder\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">System Boiler<\/span><span class=\"mwh-entry-short\">A boiler that works with a hot water cylinder but has many components built into the boiler unit.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A boiler that works with a hot water cylinder but has many components built into the boiler unit.<\/p><h3>In more detail<\/h3><p>Supplies a wet heating system and usually a separate hot-water cylinder, with certain system components built into the appliance. The exact layout varies. Cylinder capacity and reheating performance remain important hot-water considerations.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A family home can store hot water in a cylinder supplied by a system boiler.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-combi-boiler\" data-mwh-related=\"combi-boiler\">Combi Boiler<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-hot-water-cylinder\" data-mwh-related=\"hot-water-cylinder\">Hot Water Cylinder<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-system-boiler\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"T\" aria-labelledby=\"mwh-letter-T\"><h2 id=\"mwh-letter-T\" class=\"mwh-dictionary-letter\">T<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-thermal-bridge\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"T\" data-categories=\"building-fabric-insulation\" data-search=\"Thermal Bridge   An area where heat passes through the building fabric more easily, often at junctions, steelwork, lintels or gaps in insulation. An area where heat passes through the building fabric more easily, often at junctions, steelwork, lintels or gaps in insulation.In more detailA local route where heat flows more readily because of geometry, materials or gaps in insulation. It can increase heat loss and lower nearby surface temperatures. Continuous insulation and careful junction design help reduce its effects.A practical exampleAn uninsulated lintel above a window can create a colder patch inside.Related termsThese are connected ideas, rather than always exact synonyms.Cold BridgePsi Value\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Thermal Bridge<\/span><span class=\"mwh-entry-short\">An area where heat passes through the building fabric more easily, often at junctions, steelwork, lintels or gaps in insulation.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">An area where heat passes through the building fabric more easily, often at junctions, steelwork, lintels or gaps in insulation.<\/p><h3>In more detail<\/h3><p>A local route where heat flows more readily because of geometry, materials or gaps in insulation. It can increase heat loss and lower nearby surface temperatures. Continuous insulation and careful junction design help reduce its effects.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An uninsulated lintel above a window can create a colder patch inside.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-cold-bridge\" data-mwh-related=\"cold-bridge\">Cold Bridge<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-psi-value\" data-mwh-related=\"psi-value\">Psi Value<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-bridge\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-thermal-conductivity\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"T\" data-categories=\"building-fabric-insulation\" data-search=\"Thermal Conductivity   How easily heat passes through a material. How easily heat passes through a material. Lower conductivity means better insulation performance.In more detailA material property describing how readily heat is conducted, commonly in W\/(m\u00b7K). Lower values resist heat flow better for equal thickness. Moisture and test conditions can influence values; whole-element performance also depends on thickness and construction.A practical exampleA low-conductivity insulation layer can provide substantial resistance without being exceptionally thick.Related termsThese are connected ideas, rather than always exact synonyms.Lambda ValueR-Value\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Thermal Conductivity<\/span><span class=\"mwh-entry-short\">How easily heat passes through a material.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">How easily heat passes through a material. Lower conductivity means better insulation performance.<\/p><h3>In more detail<\/h3><p>A material property describing how readily heat is conducted, commonly in W\/(m\u00b7K). Lower values resist heat flow better for equal thickness. Moisture and test conditions can influence values; whole-element performance also depends on thickness and construction.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A low-conductivity insulation layer can provide substantial resistance without being exceptionally thick.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-lambda-value\" data-mwh-related=\"lambda-value\">Lambda Value<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-r-value\" data-mwh-related=\"r-value\">R-Value<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-conductivity\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-thermal-envelope\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"T\" data-categories=\"energy-performance\" data-search=\"Thermal Envelope   The parts of the building that separate heated spaces from unheated spaces or outside air. The parts of the building that separate heated spaces from unheated spaces or outside air.In more detailThe boundary around the heated part of the building, which may not follow the outside walls everywhere. Identifying it helps place insulation and airtightness layers consistently. Unheated lofts and attached garages can sit outside it.A practical exampleWith ceiling-level loft insulation, the ceiling forms the upper thermal boundary rather than the roof tiles.Related termsThese are connected ideas, rather than always exact synonyms.Building FabricUnheated Space\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Thermal Envelope<\/span><span class=\"mwh-entry-short\">The parts of the building that separate heated spaces from unheated spaces or outside air.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The parts of the building that separate heated spaces from unheated spaces or outside air.<\/p><h3>In more detail<\/h3><p>The boundary around the heated part of the building, which may not follow the outside walls everywhere. Identifying it helps place insulation and airtightness layers consistently. Unheated lofts and attached garages can sit outside it.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>With ceiling-level loft insulation, the ceiling forms the upper thermal boundary rather than the roof tiles.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-building-fabric\" data-mwh-related=\"building-fabric\">Building Fabric<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-unheated-space\" data-mwh-related=\"unheated-space\">Unheated Space<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-envelope\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-thermal-imaging\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"T\" data-categories=\"building-fabric-insulation\" data-search=\"Thermal Imaging   Using an infrared camera to examine surface-temperature patterns as part of a building investigation. Using an infrared camera to examine surface-temperature patterns as part of a building investigation.In more detailShows surface-temperature patterns, not a direct view through walls. Weather, heating, reflections and surface finishes affect interpretation. It can support an investigation but cannot by itself prove the presence of damp or quantify every heat loss.A practical exampleA cold line on an internal image may suggest a junction worth checking with other evidence.Related termsThese are connected ideas, rather than always exact synonyms.Thermal BridgeAssessment\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Thermal Imaging<\/span><span class=\"mwh-entry-short\">Using an infrared camera to examine surface-temperature patterns as part of a building investigation.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Using an infrared camera to examine surface-temperature patterns as part of a building investigation.<\/p><h3>In more detail<\/h3><p>Shows surface-temperature patterns, not a direct view through walls. Weather, heating, reflections and surface finishes affect interpretation. It can support an investigation but cannot by itself prove the presence of damp or quantify every heat loss.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A cold line on an internal image may suggest a junction worth checking with other evidence.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-bridge\" data-mwh-related=\"thermal-bridge\">Thermal Bridge<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-assessment\" data-mwh-related=\"assessment\">Assessment<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-imaging\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-thermal-mass\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"T\" data-categories=\"building-fabric-insulation\" data-search=\"Thermal Mass   The ability of materials such as brick, concrete or stone to absorb, store and release heat. The ability of materials such as brick, concrete or stone to absorb, store and release heat.In more detailDescribes the ability to absorb and release heat, rather than resist heat flow. Its usefulness depends on exposure, temperatures and timing. Heavy materials can moderate temperature swings but do not replace insulation or a summer ventilation strategy.A practical exampleAn exposed masonry floor can absorb daytime heat and release it when the room becomes cooler.Related termsThese are connected ideas, rather than always exact synonyms.InsulationOverheating\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Thermal Mass<\/span><span class=\"mwh-entry-short\">The ability of materials such as brick, concrete or stone to absorb, store and release heat.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The ability of materials such as brick, concrete or stone to absorb, store and release heat.<\/p><h3>In more detail<\/h3><p>Describes the ability to absorb and release heat, rather than resist heat flow. Its usefulness depends on exposure, temperatures and timing. Heavy materials can moderate temperature swings but do not replace insulation or a summer ventilation strategy.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An exposed masonry floor can absorb daytime heat and release it when the room becomes cooler.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-insulation\" data-mwh-related=\"insulation\">Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-overheating\" data-mwh-related=\"overheating\">Overheating<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-mass\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-thermostat\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"T\" data-categories=\"controls\" data-search=\"Thermostat   A control that turns heating on or off, or modulates it, based on temperature. A control that turns heating on or off, or modulates it, based on temperature.In more detailMeasures temperature at its position and signals a control system. Location matters: sunlight, draughts and nearby heat sources can distort its view of room comfort. A room thermostat differs from a boiler water-temperature setting.A practical exampleA thermostat beside a radiator may stop heating before the rest of the room is comfortable.Related termsThese are connected ideas, rather than always exact synonyms.Heating ControlsThermostatic Radiator Valve\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Thermostat<\/span><span class=\"mwh-entry-short\">A control that turns heating on or off, or modulates it, based on temperature.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A control that turns heating on or off, or modulates it, based on temperature.<\/p><h3>In more detail<\/h3><p>Measures temperature at its position and signals a control system. Location matters: sunlight, draughts and nearby heat sources can distort its view of room comfort. A room thermostat differs from a boiler water-temperature setting.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A thermostat beside a radiator may stop heating before the rest of the room is comfortable.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heating-controls\" data-mwh-related=\"heating-controls\">Heating Controls<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermostatic-radiator-valve\" data-mwh-related=\"thermostatic-radiator-valve\">Thermostatic Radiator Valve<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermostat\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-thermostatic-radiator-valve\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"T\" data-categories=\"controls\" data-search=\"Thermostatic Radiator Valve TRV TRV A valve fitted to a radiator that helps control the temperature in an individual room. A valve fitted to a radiator that helps control the temperature in an individual room.Also called: TRVIn more detailRegulates water through an individual radiator in response to nearby air temperature. It does not normally set the boiler&#039;s water temperature. Valve arrangements need coordination with the main thermostat and the system&#039;s minimum-flow requirements.A practical exampleTurning a TRV down can limit a bedroom temperature while other rooms continue heating.Related termsThese are connected ideas, rather than always exact synonyms.ThermostatHeating Controls\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Thermostatic Radiator Valve <span class=\"mwh-entry-acronym\">TRV<\/span><\/span><span class=\"mwh-entry-short\">A valve fitted to a radiator that helps control the temperature in an individual room.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A valve fitted to a radiator that helps control the temperature in an individual room.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> TRV<\/p><h3>In more detail<\/h3><p>Regulates water through an individual radiator in response to nearby air temperature. It does not normally set the boiler&#039;s water temperature. Valve arrangements need coordination with the main thermostat and the system&#039;s minimum-flow requirements.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Turning a TRV down can limit a bedroom temperature while other rooms continue heating.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermostat\" data-mwh-related=\"thermostat\">Thermostat<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heating-controls\" data-mwh-related=\"heating-controls\">Heating Controls<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermostatic-radiator-valve\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-timber-frame\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"T\" data-categories=\"building-fabric-insulation\" data-search=\"Timber Frame   A construction type where the main structural frame is made from timber. A construction type where the main structural frame is made from timber.In more detailUses a timber structural frame, with sheathing, insulation and finishes forming a layered wall or roof. The outside appearance may resemble masonry construction. Moisture management, ventilation cavities and fire details must suit the actual build-up.A practical exampleA brick-clad timber-frame wall should not be assumed to be an ordinary masonry cavity wall suitable for filling.Related termsThese are connected ideas, rather than always exact synonyms.Non-Traditional ConstructionVapour Control Layer\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Timber Frame<\/span><span class=\"mwh-entry-short\">A construction type where the main structural frame is made from timber.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A construction type where the main structural frame is made from timber.<\/p><h3>In more detail<\/h3><p>Uses a timber structural frame, with sheathing, insulation and finishes forming a layered wall or roof. The outside appearance may resemble masonry construction. Moisture management, ventilation cavities and fire details must suit the actual build-up.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A brick-clad timber-frame wall should not be assumed to be an ordinary masonry cavity wall suitable for filling.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-non-traditional-construction\" data-mwh-related=\"non-traditional-construction\">Non-Traditional Construction<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-vapour-control-layer\" data-mwh-related=\"vapour-control-layer\">Vapour Control Layer<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-timber-frame\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-trickle-vent\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"T\" data-categories=\"controls\" data-search=\"Trickle Vent   A small controllable vent, usually in a window frame, that provides background ventilation. A small controllable vent, usually in a window frame, that provides background ventilation.In more detailA small controlled opening normally providing background air to a room. It needs to be considered with extraction elsewhere and air-transfer paths. It is not a substitute for all ventilation needs or a defect to seal during draught-proofing.A practical exampleA window replacement should retain or provide the ventilation required by the dwelling&#039;s strategy.Related termsThese are connected ideas, rather than always exact synonyms.Background VentilationVentilation Strategy\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Trickle Vent<\/span><span class=\"mwh-entry-short\">A small controllable vent, usually in a window frame, that provides background ventilation.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A small controllable vent, usually in a window frame, that provides background ventilation.<\/p><h3>In more detail<\/h3><p>A small controlled opening normally providing background air to a room. It needs to be considered with extraction elsewhere and air-transfer paths. It is not a substitute for all ventilation needs or a defect to seal during draught-proofing.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A window replacement should retain or provide the ventilation required by the dwelling&#039;s strategy.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-background-ventilation\" data-mwh-related=\"background-ventilation\">Background Ventilation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ventilation-strategy\" data-mwh-related=\"ventilation-strategy\">Ventilation Strategy<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-trickle-vent\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-trustmark\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"T\" data-categories=\"retrofit-standards\" data-search=\"TrustMark   A UK government-endorsed quality scheme used for many retrofit and energy-efficiency works. A UK government-endorsed quality scheme used for many retrofit and energy-efficiency works.In more detailA government-endorsed quality scheme covering registered businesses within defined work categories. Check current registration and scope, not just a badge on an advert. Registration does not remove the need for a suitable design, contract and project evidence.A practical exampleA homeowner checks that the business is registered for the particular work being proposed.Related termsThese are connected ideas, rather than always exact synonyms.Quality AssuranceRetrofit Installer\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">TrustMark<\/span><span class=\"mwh-entry-short\">A UK government-endorsed quality scheme used for many retrofit and energy-efficiency works.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A UK government-endorsed quality scheme used for many retrofit and energy-efficiency works.<\/p><h3>In more detail<\/h3><p>A government-endorsed quality scheme covering registered businesses within defined work categories. Check current registration and scope, not just a badge on an advert. Registration does not remove the need for a suitable design, contract and project evidence.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A homeowner checks that the business is registered for the particular work being proposed.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-quality-assurance\" data-mwh-related=\"quality-assurance\">Quality Assurance<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-installer\" data-mwh-related=\"retrofit-installer\">Retrofit Installer<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-trustmark\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"U\" aria-labelledby=\"mwh-letter-U\"><h2 id=\"mwh-letter-U\" class=\"mwh-dictionary-letter\">U<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-u-value\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"U\" data-categories=\"building-fabric-insulation\" data-search=\"U-Value   A measure of how much heat passes through a building element, such as a wall, roof, floor, window or door. A measure of how much heat passes through a building element, such as a wall, roof, floor, window or door. The lower the U-value, the better the insulation performance.In more detailDescribes heat flow through an area of a complete building element per degree of temperature difference, normally in W\/(m\u00b2\u00b7K). Lower values mean less heat transfer. It differs from conductivity, which describes a material rather than the whole element.A practical exampleA wall U-value includes the effect of its layers, not just the insulation product&#039;s conductivity.Related termsThese are connected ideas, rather than always exact synonyms.R-ValueThermal Conductivity\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">U-Value<\/span><span class=\"mwh-entry-short\">A measure of how much heat passes through a building element, such as a wall, roof, floor, window or door.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A measure of how much heat passes through a building element, such as a wall, roof, floor, window or door. The lower the U-value, the better the insulation performance.<\/p><h3>In more detail<\/h3><p>Describes heat flow through an area of a complete building element per degree of temperature difference, normally in W\/(m\u00b2\u00b7K). Lower values mean less heat transfer. It differs from conductivity, which describes a material rather than the whole element.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A wall U-value includes the effect of its layers, not just the insulation product&#039;s conductivity.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-r-value\" data-mwh-related=\"r-value\">R-Value<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-conductivity\" data-mwh-related=\"thermal-conductivity\">Thermal Conductivity<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-u-value\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-underfloor-heating\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"U\" data-categories=\"heating-hot-water\" data-search=\"Underfloor Heating UFH UFH A heating system with pipes or electric elements installed in or under the floor. A heating system with pipes or electric elements installed in or under the floor. Wet underfloor heating can work well with heat pumps because it can run at low temperatures.Also called: UFHIn more detailCan use circulating water in pipes or electric resistance elements. These systems have different running characteristics. Output depends on floor construction, coverings, available area and temperatures; suitability should be checked against each room&#039;s heat loss.A practical exampleA thick carpet can restrict heat delivery compared with a suitable low-resistance floor finish.Related termsThese are connected ideas, rather than always exact synonyms.Emitter SizingLow Temperature Heating\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Underfloor Heating <span class=\"mwh-entry-acronym\">UFH<\/span><\/span><span class=\"mwh-entry-short\">A heating system with pipes or electric elements installed in or under the floor.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A heating system with pipes or electric elements installed in or under the floor. Wet underfloor heating can work well with heat pumps because it can run at low temperatures.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> UFH<\/p><h3>In more detail<\/h3><p>Can use circulating water in pipes or electric resistance elements. These systems have different running characteristics. Output depends on floor construction, coverings, available area and temperatures; suitability should be checked against each room&#039;s heat loss.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A thick carpet can restrict heat delivery compared with a suitable low-resistance floor finish.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-emitter-sizing\" data-mwh-related=\"emitter-sizing\">Emitter Sizing<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-low-temperature-heating\" data-mwh-related=\"low-temperature-heating\">Low Temperature Heating<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-underfloor-heating\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-underfloor-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"U\" data-categories=\"building-fabric-insulation\" data-search=\"Underfloor Insulation UFI UFI Insulation installed below a floor, commonly between suspended timber floor joists. Insulation installed below a floor, commonly between suspended timber floor joists.Also called: UFIIn more detailDescribes insulation placed below a floor surface, often between or beneath suspended timber joists. Support, wind washing, services and moisture behaviour need attention. It should not obstruct the ventilation required to keep the floor structure healthy.A practical exampleInsulation is supported under boards while a clear ventilated void remains below.Related termsThese are connected ideas, rather than always exact synonyms.Suspended Timber FloorFloor Insulation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Underfloor Insulation <span class=\"mwh-entry-acronym\">UFI<\/span><\/span><span class=\"mwh-entry-short\">Insulation installed below a floor, commonly between suspended timber floor joists.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Insulation installed below a floor, commonly between suspended timber floor joists.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> UFI<\/p><h3>In more detail<\/h3><p>Describes insulation placed below a floor surface, often between or beneath suspended timber joists. Support, wind washing, services and moisture behaviour need attention. It should not obstruct the ventilation required to keep the floor structure healthy.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Insulation is supported under boards while a clear ventilated void remains below.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-suspended-timber-floor\" data-mwh-related=\"suspended-timber-floor\">Suspended Timber Floor<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-floor-insulation\" data-mwh-related=\"floor-insulation\">Floor Insulation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-underfloor-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-unheated-space\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"U\" data-categories=\"energy-performance\" data-search=\"Unheated Space   An area such as a loft, garage, cellar or porch that is not normally heated. An area such as a loft, garage, cellar or porch that is not normally heated.In more detailA space not normally maintained at the dwelling&#039;s comfort temperature. Heat can still flow into it from neighbouring rooms. Whether it belongs inside or outside the thermal envelope affects insulation and heating calculations.A practical exampleA room above an unheated garage may need an insulated floor between the two spaces.Related termsThese are connected ideas, rather than always exact synonyms.Thermal EnvelopeHeat Loss Calculation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Unheated Space<\/span><span class=\"mwh-entry-short\">An area such as a loft, garage, cellar or porch that is not normally heated.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">An area such as a loft, garage, cellar or porch that is not normally heated.<\/p><h3>In more detail<\/h3><p>A space not normally maintained at the dwelling&#039;s comfort temperature. Heat can still flow into it from neighbouring rooms. Whether it belongs inside or outside the thermal envelope affects insulation and heating calculations.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A room above an unheated garage may need an insulated floor between the two spaces.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-envelope\" data-mwh-related=\"thermal-envelope\">Thermal Envelope<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-loss-calculation\" data-mwh-related=\"heat-loss-calculation\">Heat Loss Calculation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-unheated-space\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"V\" aria-labelledby=\"mwh-letter-V\"><h2 id=\"mwh-letter-V\" class=\"mwh-dictionary-letter\">V<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-vapour-barrier\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"V\" data-categories=\"moisture-damp\" data-search=\"Vapour Barrier   A layer designed to stop or reduce water vapour passing through a building element. A layer designed to stop or reduce water vapour passing through a building element.In more detailAn informal name for a layer with high resistance to water-vapour diffusion. The specified resistance and installation details matter more than the label. It is not automatically the same as an airtightness layer or a waterproof covering.A practical exampleAn unsuitable high-resistance layer can restrict drying if placed in the wrong construction.Related termsThese are connected ideas, rather than always exact synonyms.Vapour Control LayerBreathability\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Vapour Barrier<\/span><span class=\"mwh-entry-short\">A layer designed to stop or reduce water vapour passing through a building element.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A layer designed to stop or reduce water vapour passing through a building element.<\/p><h3>In more detail<\/h3><p>An informal name for a layer with high resistance to water-vapour diffusion. The specified resistance and installation details matter more than the label. It is not automatically the same as an airtightness layer or a waterproof covering.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An unsuitable high-resistance layer can restrict drying if placed in the wrong construction.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-vapour-control-layer\" data-mwh-related=\"vapour-control-layer\">Vapour Control Layer<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-breathability\" data-mwh-related=\"breathability\">Breathability<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-vapour-barrier\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-vapour-control-layer\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"V\" data-categories=\"controls\" data-search=\"Vapour Control Layer VCL VCL A material used to control the movement of moisture vapour through walls, roofs or floors. A material used to control the movement of moisture vapour through walls, roofs or floors.Also called: VCLIn more detailLimits vapour movement according to the design, rather than necessarily blocking it completely. Continuity at joints and penetrations matters. Its position and resistance should suit climate, materials and drying paths; it is not universally correct to add one everywhere.A practical exampleA roof design may specify a carefully sealed control layer on the room side of the insulation.Related termsThese are connected ideas, rather than always exact synonyms.Vapour Barrierhygrothermal assessment\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Vapour Control Layer <span class=\"mwh-entry-acronym\">VCL<\/span><\/span><span class=\"mwh-entry-short\">A material used to control the movement of moisture vapour through walls, roofs or floors.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A material used to control the movement of moisture vapour through walls, roofs or floors.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> VCL<\/p><h3>In more detail<\/h3><p>Limits vapour movement according to the design, rather than necessarily blocking it completely. Continuity at joints and penetrations matters. Its position and resistance should suit climate, materials and drying paths; it is not universally correct to add one everywhere.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A roof design may specify a carefully sealed control layer on the room side of the insulation.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-vapour-barrier\" data-mwh-related=\"vapour-barrier\">Vapour Barrier<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-hygrothermal-assessment\" data-mwh-related=\"hygrothermal-assessment\">hygrothermal assessment<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-vapour-control-layer\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-ventilation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"V\" data-categories=\"controls\" data-search=\"Ventilation   The controlled supply and removal of air from a home. The controlled supply and removal of air from a home. Ventilation helps manage moisture, odours, pollutants and indoor air quality.In more detailDeliberately replaces indoor air to manage moisture and pollutants. Supply, extraction and transfer routes must work together. Reducing uncontrolled leakage should not reduce the fresh-air provision needed for occupants or safe appliance operation.A practical exampleA ventilation strategy may combine bedroom air inlets with continuous bathroom extraction.Related termsThese are connected ideas, rather than always exact synonyms.Background VentilationMechanical Extract Ventilation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Ventilation<\/span><span class=\"mwh-entry-short\">The controlled supply and removal of air from a home.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The controlled supply and removal of air from a home. Ventilation helps manage moisture, odours, pollutants and indoor air quality.<\/p><h3>In more detail<\/h3><p>Deliberately replaces indoor air to manage moisture and pollutants. Supply, extraction and transfer routes must work together. Reducing uncontrolled leakage should not reduce the fresh-air provision needed for occupants or safe appliance operation.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A ventilation strategy may combine bedroom air inlets with continuous bathroom extraction.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-background-ventilation\" data-mwh-related=\"background-ventilation\">Background Ventilation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-mechanical-extract-ventilation\" data-mwh-related=\"mechanical-extract-ventilation\">Mechanical Extract Ventilation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ventilation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-ventilation-heat-loss\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"V\" data-categories=\"ventilation-air-quality\" data-search=\"Ventilation Heat Loss   Heat lost when warm indoor air is replaced by colder outside air. Heat lost when warm indoor air is replaced by colder outside air.In more detailHeat carried away when indoor air is replaced by cooler outdoor air. Both necessary ventilation and uncontrolled leakage can contribute. Heat recovery may reduce some losses, but maintaining suitable air quality remains essential.A practical exampleAn MVHR heat exchanger transfers some outgoing heat to incoming air while still replacing stale air.Related termsThese are connected ideas, rather than always exact synonyms.Mechanical Ventilation with Heat RecoveryAir Tightness\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Ventilation Heat Loss<\/span><span class=\"mwh-entry-short\">Heat lost when warm indoor air is replaced by colder outside air.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Heat lost when warm indoor air is replaced by colder outside air.<\/p><h3>In more detail<\/h3><p>Heat carried away when indoor air is replaced by cooler outdoor air. Both necessary ventilation and uncontrolled leakage can contribute. Heat recovery may reduce some losses, but maintaining suitable air quality remains essential.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An MVHR heat exchanger transfers some outgoing heat to incoming air while still replacing stale air.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-mechanical-ventilation-with-heat-recovery\" data-mwh-related=\"mechanical-ventilation-with-heat-recovery\">Mechanical Ventilation with Heat Recovery<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-tightness\" data-mwh-related=\"air-tightness\">Air Tightness<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ventilation-heat-loss\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-ventilation-rate\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"V\" data-categories=\"ventilation-air-quality\" data-search=\"Ventilation Rate   The amount of air supplied to or removed from a building over time. The amount of air supplied to or removed from a building over time.In more detailQuantifies airflow, often in litres per second, cubic metres per hour or air changes per hour. These units describe different comparisons. Check whether a figure is a design requirement, a measured airflow or a pressure-test result.A practical exampleAn installer measures an extract point in litres per second during commissioning.Related termsThese are connected ideas, rather than always exact synonyms.Air Changes per HourCommissioning\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Ventilation Rate<\/span><span class=\"mwh-entry-short\">The amount of air supplied to or removed from a building over time.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The amount of air supplied to or removed from a building over time.<\/p><h3>In more detail<\/h3><p>Quantifies airflow, often in litres per second, cubic metres per hour or air changes per hour. These units describe different comparisons. Check whether a figure is a design requirement, a measured airflow or a pressure-test result.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An installer measures an extract point in litres per second during commissioning.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-air-changes-per-hour\" data-mwh-related=\"air-changes-per-hour\">Air Changes per Hour<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-commissioning\" data-mwh-related=\"commissioning\">Commissioning<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ventilation-rate\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-ventilation-strategy\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"V\" data-categories=\"ventilation-air-quality\" data-search=\"Ventilation Strategy   A planned approach to providing enough fresh air before and after retrofit works. A planned approach to providing enough fresh air before and after retrofit works.In more detailA coordinated plan for outdoor air supply, extraction, transfer routes, controls and maintenance. It should consider occupancy and the completed building after improvements. Buying one fan does not automatically establish a suitable whole-dwelling strategy.A practical exampleNew windows and insulation are planned alongside the air inlets and extraction the renovated home needs.Related termsThese are connected ideas, rather than always exact synonyms.VentilationWhole-House Approach\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Ventilation Strategy<\/span><span class=\"mwh-entry-short\">A planned approach to providing enough fresh air before and after retrofit works.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A planned approach to providing enough fresh air before and after retrofit works.<\/p><h3>In more detail<\/h3><p>A coordinated plan for outdoor air supply, extraction, transfer routes, controls and maintenance. It should consider occupancy and the completed building after improvements. Buying one fan does not automatically establish a suitable whole-dwelling strategy.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>New windows and insulation are planned alongside the air inlets and extraction the renovated home needs.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ventilation\" data-mwh-related=\"ventilation\">Ventilation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-whole-house-approach\" data-mwh-related=\"whole-house-approach\">Whole-House Approach<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-ventilation-strategy\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-volumiser\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"V\" data-categories=\"heating-hot-water\" data-search=\"Volumiser   A vessel used in some heat pump systems to increase system water volume and help stable operation. A vessel used in some heat pump systems to increase system water volume and help stable operation.In more detailAdds water volume to a heating circuit, helping meet a heat pump&#039;s minimum volume requirements. It is not necessarily a hydraulic separator or hot-water store. Whether it is needed depends on the manufacturer&#039;s requirements and system design.A practical exampleA designer adds a vessel where a small radiator circuit otherwise contains insufficient water volume.Related termsThese are connected ideas, rather than always exact synonyms.Inverter CompressorHeat Pump\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Volumiser<\/span><span class=\"mwh-entry-short\">A vessel used in some heat pump systems to increase system water volume and help stable operation.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A vessel used in some heat pump systems to increase system water volume and help stable operation.<\/p><h3>In more detail<\/h3><p>Adds water volume to a heating circuit, helping meet a heat pump&#039;s minimum volume requirements. It is not necessarily a hydraulic separator or hot-water store. Whether it is needed depends on the manufacturer&#039;s requirements and system design.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A designer adds a vessel where a small radiator circuit otherwise contains insufficient water volume.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-inverter-compressor\" data-mwh-related=\"inverter-compressor\">Inverter Compressor<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-pump\" data-mwh-related=\"heat-pump\">Heat Pump<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-volumiser\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"W\" aria-labelledby=\"mwh-letter-W\"><h2 id=\"mwh-letter-W\" class=\"mwh-dictionary-letter\">W<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-warm-roof\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"W\" data-categories=\"building-fabric-insulation\" data-search=\"Warm Roof   A roof construction where insulation is installed above the roof deck, helping keep the structure warm. A roof construction where insulation is installed above the roof deck, helping keep the structure warm.In more detailUsually places insulation above the structural deck or supporting roof structure in the relevant roof design. The full build-up includes moisture control and weather protection. The phrase does not simply mean a roof that feels warm indoors.A practical exampleA flat-roof refurbishment can put insulation above the deck beneath an appropriate waterproofing system.Related termsThese are connected ideas, rather than always exact synonyms.Flat Roof InsulationVapour Control Layer\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Warm Roof<\/span><span class=\"mwh-entry-short\">A roof construction where insulation is installed above the roof deck, helping keep the structure warm.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A roof construction where insulation is installed above the roof deck, helping keep the structure warm.<\/p><h3>In more detail<\/h3><p>Usually places insulation above the structural deck or supporting roof structure in the relevant roof design. The full build-up includes moisture control and weather protection. The phrase does not simply mean a roof that feels warm indoors.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A flat-roof refurbishment can put insulation above the deck beneath an appropriate waterproofing system.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flat-roof-insulation\" data-mwh-related=\"flat-roof-insulation\">Flat Roof Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-vapour-control-layer\" data-mwh-related=\"vapour-control-layer\">Vapour Control Layer<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-warm-roof\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-water-source-heat-pump\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"W\" data-categories=\"heating-hot-water\" data-search=\"Water Source Heat Pump WSHP WSHP A heat pump that collects heat from a water source such as a lake, river, pond, well or open-loop system. A heat pump that collects heat from a water source such as a lake, river, pond, well or open-loop system.Also called: WSHPIn more detailCollects heat from water using an appropriate open-loop or closed-loop arrangement. Source temperature, flow, water quality and permissions can affect feasibility. Specialist environmental and system-design advice is normally needed.A practical exampleA closed collector submerged in suitable water transfers heat through pipework without taking the source water indoors.Related termsThese are connected ideas, rather than always exact synonyms.Heat PumpHeat Exchanger\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Water Source Heat Pump <span class=\"mwh-entry-acronym\">WSHP<\/span><\/span><span class=\"mwh-entry-short\">A heat pump that collects heat from a water source such as a lake, river, pond, well or open-loop system.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A heat pump that collects heat from a water source such as a lake, river, pond, well or open-loop system.<\/p><p class=\"mwh-entry-aliases\"><strong>Also called:<\/strong> WSHP<\/p><h3>In more detail<\/h3><p>Collects heat from water using an appropriate open-loop or closed-loop arrangement. Source temperature, flow, water quality and permissions can affect feasibility. Specialist environmental and system-design advice is normally needed.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A closed collector submerged in suitable water transfers heat through pipework without taking the source water indoors.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-pump\" data-mwh-related=\"heat-pump\">Heat Pump<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heat-exchanger\" data-mwh-related=\"heat-exchanger\">Heat Exchanger<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-water-source-heat-pump\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-weather-compensation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"W\" data-categories=\"controls\" data-search=\"Weather Compensation   A control method that adjusts heating flow temperature based on the outside temperature. A control method that adjusts heating flow temperature based on the outside temperature.In more detailUses outdoor temperature to adjust the target heating-water temperature. It needs an appropriate heating curve and system setup. It differs from merely turning heating on when the weather forecast predicts a cold day.A practical exampleThe controller gradually raises flow temperature as the outside temperature falls.Related termsThese are connected ideas, rather than always exact synonyms.Heating CurveCompensation Controls\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Weather Compensation<\/span><span class=\"mwh-entry-short\">A control method that adjusts heating flow temperature based on the outside temperature.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A control method that adjusts heating flow temperature based on the outside temperature.<\/p><h3>In more detail<\/h3><p>Uses outdoor temperature to adjust the target heating-water temperature. It needs an appropriate heating curve and system setup. It differs from merely turning heating on when the weather forecast predicts a cold day.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>The controller gradually raises flow temperature as the outside temperature falls.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heating-curve\" data-mwh-related=\"heating-curve\">Heating Curve<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-compensation-controls\" data-mwh-related=\"compensation-controls\">Compensation Controls<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-weather-compensation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-weatherproofing\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"W\" data-categories=\"moisture-damp\" data-search=\"Weatherproofing   Protecting a building from rain, wind and external moisture. Protecting a building from rain, wind and external moisture.In more detailControls rain and wind at roofs, walls, openings and joints. It should allow the complete construction to manage moisture appropriately. Applying an impermeable coating without diagnosing water entry can conceal defects or hinder drying.A practical exampleRepairing a gutter or flashing can be more relevant than treating an internal damp stain.Related termsThese are connected ideas, rather than always exact synonyms.Penetrating DampRender\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Weatherproofing<\/span><span class=\"mwh-entry-short\">Protecting a building from rain, wind and external moisture.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Protecting a building from rain, wind and external moisture.<\/p><h3>In more detail<\/h3><p>Controls rain and wind at roofs, walls, openings and joints. It should allow the complete construction to manage moisture appropriately. Applying an impermeable coating without diagnosing water entry can conceal defects or hinder drying.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Repairing a gutter or flashing can be more relevant than treating an internal damp stain.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-penetrating-damp\" data-mwh-related=\"penetrating-damp\">Penetrating Damp<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-render\" data-mwh-related=\"render\">Render<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-weatherproofing\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-wet-room-extract\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"W\" data-categories=\"ventilation-air-quality\" data-search=\"Wet Room Extract   Ventilation that extracts moist air from bathrooms, shower rooms, kitchens and utility rooms. Ventilation that extracts moist air from bathrooms, shower rooms, kitchens and utility rooms.In more detailExtracts air from rooms with concentrated moisture or pollutants. Here, wet room means spaces such as kitchens and bathrooms, not only a level-access shower room. Ducting, replacement air and measured flow determine effectiveness.A practical exampleBathroom extraction removes moisture close to the shower before it spreads to bedrooms.Related termsThese are connected ideas, rather than always exact synonyms.Extractor FanMechanical Extract Ventilation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Wet Room Extract<\/span><span class=\"mwh-entry-short\">Ventilation that extracts moist air from bathrooms, shower rooms, kitchens and utility rooms.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Ventilation that extracts moist air from bathrooms, shower rooms, kitchens and utility rooms.<\/p><h3>In more detail<\/h3><p>Extracts air from rooms with concentrated moisture or pollutants. Here, wet room means spaces such as kitchens and bathrooms, not only a level-access shower room. Ducting, replacement air and measured flow determine effectiveness.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Bathroom extraction removes moisture close to the shower before it spreads to bedrooms.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-extractor-fan\" data-mwh-related=\"extractor-fan\">Extractor Fan<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-mechanical-extract-ventilation\" data-mwh-related=\"mechanical-extract-ventilation\">Mechanical Extract Ventilation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-wet-room-extract\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-whole-house-approach\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"W\" data-categories=\"ventilation-air-quality\" data-search=\"Whole-House Approach   A retrofit method that considers the whole property rather than installing individual measures in isolation. A retrofit method that considers the whole property rather than installing individual measures in isolation.In more detailConsiders the home as interacting construction, services and people. It avoids choosing isolated measures without checking their combined effect. Ventilation, moisture, energy, comfort, heritage and future maintenance should be considered together.A practical exampleMaking windows more airtight prompts a review of fresh-air supply rather than treating glazing as a standalone purchase.Related termsThese are connected ideas, rather than always exact synonyms.RetrofitRetrofit Plan\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Whole-House Approach<\/span><span class=\"mwh-entry-short\">A retrofit method that considers the whole property rather than installing individual measures in isolation.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A retrofit method that considers the whole property rather than installing individual measures in isolation.<\/p><h3>In more detail<\/h3><p>Considers the home as interacting construction, services and people. It avoids choosing isolated measures without checking their combined effect. Ventilation, moisture, energy, comfort, heritage and future maintenance should be considered together.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Making windows more airtight prompts a review of fresh-air supply rather than treating glazing as a standalone purchase.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit\" data-mwh-related=\"retrofit\">Retrofit<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-plan\" data-mwh-related=\"retrofit-plan\">Retrofit Plan<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-whole-house-approach\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-whole-house-retrofit-plan\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"W\" data-categories=\"ventilation-air-quality\" data-search=\"Whole-House Retrofit Plan   A staged improvement plan that considers insulation, heating, ventilation, moisture, comfort, cost and future works. A staged improvement plan that considers insulation, heating, ventilation, moisture, comfort, cost and future works.In more detailRecords a coordinated sequence of improvements tailored to the dwelling and household objectives. It can allow work in stages while anticipating interfaces and later measures. It should be updated when condition, budgets or planned work change.A practical exampleA wall-insulation detail allows for a future roof upgrade instead of creating a junction that must be rebuilt.Related termsThese are connected ideas, rather than always exact synonyms.Retrofit PlanWhole-House Approach\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Whole-House Retrofit Plan<\/span><span class=\"mwh-entry-short\">A staged improvement plan that considers insulation, heating, ventilation, moisture, comfort, cost and future works.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A staged improvement plan that considers insulation, heating, ventilation, moisture, comfort, cost and future works.<\/p><h3>In more detail<\/h3><p>Records a coordinated sequence of improvements tailored to the dwelling and household objectives. It can allow work in stages while anticipating interfaces and later measures. It should be updated when condition, budgets or planned work change.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A wall-insulation detail allows for a future roof upgrade instead of creating a junction that must be rebuilt.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-retrofit-plan\" data-mwh-related=\"retrofit-plan\">Retrofit Plan<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-whole-house-approach\" data-mwh-related=\"whole-house-approach\">Whole-House Approach<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-whole-house-retrofit-plan\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-window-reveal\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"W\" data-categories=\"building-fabric-insulation\" data-search=\"Window Reveal   The area around the window opening. The area around the window opening. Reveals are important because they can create thermal bridges if not insulated properly.In more detailThe sides, head and sill surfaces of a window opening. Insulation, weather seals and airtightness need to connect around them. A reveal left untreated can remain a local cold surface even after the main wall is improved.A practical exampleAn insulated wall design includes return insulation at a window where appropriate and practical.Related termsThese are connected ideas, rather than always exact synonyms.Thermal BridgeExternal Wall Insulation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Window Reveal<\/span><span class=\"mwh-entry-short\">The area around the window opening.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">The area around the window opening. Reveals are important because they can create thermal bridges if not insulated properly.<\/p><h3>In more detail<\/h3><p>The sides, head and sill surfaces of a window opening. Insulation, weather seals and airtightness need to connect around them. A reveal left untreated can remain a local cold surface even after the main wall is improved.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>An insulated wall design includes return insulation at a window where appropriate and practical.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-thermal-bridge\" data-mwh-related=\"thermal-bridge\">Thermal Bridge<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-external-wall-insulation\" data-mwh-related=\"external-wall-insulation\">External Wall Insulation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-window-reveal\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"X\" aria-labelledby=\"mwh-letter-X\"><h2 id=\"mwh-letter-X\" class=\"mwh-dictionary-letter\">X<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-xps-insulation\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"X\" data-categories=\"moisture-damp\" data-search=\"XPS Insulation   Extruded polystyrene insulation. Extruded polystyrene insulation. A rigid foam insulation often used where moisture resistance and compressive strength are needed.In more detailExtruded polystyrene is a rigid foam used where specified strength and moisture resistance are useful. Those properties do not make every XPS board suitable for every application. Fire, load, thickness and system requirements still need checking.A practical exampleA suitable floor specification may use XPS beneath a load-bearing finish.Related termsThese are connected ideas, rather than always exact synonyms.InsulationSolid Floor Insulation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">XPS Insulation<\/span><span class=\"mwh-entry-short\">Extruded polystyrene insulation.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Extruded polystyrene insulation. A rigid foam insulation often used where moisture resistance and compressive strength are needed.<\/p><h3>In more detail<\/h3><p>Extruded polystyrene is a rigid foam used where specified strength and moisture resistance are useful. Those properties do not make every XPS board suitable for every application. Fire, load, thickness and system requirements still need checking.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A suitable floor specification may use XPS beneath a load-bearing finish.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-insulation\" data-mwh-related=\"insulation\">Insulation<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-solid-floor-insulation\" data-mwh-related=\"solid-floor-insulation\">Solid Floor Insulation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-xps-insulation\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t\t\t<section class=\"mwh-dictionary-section\" data-letter-group=\"Z\" aria-labelledby=\"mwh-letter-Z\"><h2 id=\"mwh-letter-Z\" class=\"mwh-dictionary-letter\">Z<\/h2><div class=\"mwh-dictionary-list\">\n\t\t\t\t\t\t\t\t<article id=\"mwh-glossary-zero-carbon\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"Z\" data-categories=\"renewables-electricity\" data-search=\"Zero Carbon   A claim about carbon emissions that needs a clear boundary, time period and accounting method. A claim about carbon emissions that needs a clear boundary, time period and accounting method.In more detailA claim that needs a defined boundary, period and method. Direct fuel use, purchased energy, embodied emissions and offsets are different considerations. Without that explanation, it is impossible to compare the claim reliably.A practical exampleA home with no on-site fuel burning can still have emissions associated with its electricity and construction.Related termsThese are connected ideas, rather than always exact synonyms.Zero Direct Emissions HeatingDecarbonisation\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Zero Carbon<\/span><span class=\"mwh-entry-short\">A claim about carbon emissions that needs a clear boundary, time period and accounting method.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">A claim about carbon emissions that needs a clear boundary, time period and accounting method.<\/p><h3>In more detail<\/h3><p>A claim that needs a defined boundary, period and method. Direct fuel use, purchased energy, embodied emissions and offsets are different considerations. Without that explanation, it is impossible to compare the claim reliably.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A home with no on-site fuel burning can still have emissions associated with its electricity and construction.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-zero-direct-emissions-heating\" data-mwh-related=\"zero-direct-emissions-heating\">Zero Direct Emissions Heating<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-decarbonisation\" data-mwh-related=\"decarbonisation\">Decarbonisation<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-zero-carbon\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-zero-direct-emissions-heating\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"Z\" data-categories=\"heating-hot-water\" data-search=\"Zero Direct Emissions Heating   Heating with no combustion emissions at its point of use; electricity supply and equipment manufacture can still cause emissions. Heating with no combustion emissions at its point of use; electricity supply and equipment manufacture can still cause emissions.In more detailProduces no combustion emissions at the point of heating use, unlike an appliance burning fuel indoors or on site. It does not mean zero lifecycle or electricity-generation emissions. Efficiency still determines how much electricity the service requires.A practical exampleA heat pump and an electric panel heater both avoid on-site combustion but can use very different amounts of electricity.Related termsThese are connected ideas, rather than always exact synonyms.Low Carbon HeatingDirect Electric Heating\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Zero Direct Emissions Heating<\/span><span class=\"mwh-entry-short\">Heating with no combustion emissions at its point of use; electricity supply and equipment manufacture can still cause emissions.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Heating with no combustion emissions at its point of use; electricity supply and equipment manufacture can still cause emissions.<\/p><h3>In more detail<\/h3><p>Produces no combustion emissions at the point of heating use, unlike an appliance burning fuel indoors or on site. It does not mean zero lifecycle or electricity-generation emissions. Efficiency still determines how much electricity the service requires.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>A heat pump and an electric panel heater both avoid on-site combustion but can use very different amounts of electricity.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-low-carbon-heating\" data-mwh-related=\"low-carbon-heating\">Low Carbon Heating<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-direct-electric-heating\" data-mwh-related=\"direct-electric-heating\">Direct Electric Heating<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-zero-direct-emissions-heating\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t\t\t\t\t<article id=\"mwh-glossary-zoning\" class=\"mwh-dictionary-item\" data-mwh-glossary-entry data-letter=\"Z\" data-categories=\"controls\" data-search=\"Zoning   Dividing a heating system into separate areas that can be controlled independently, improving comfort and efficiency. Dividing a heating system into separate areas that can be controlled independently, improving comfort and efficiency.In more detailAllows different areas or circuits to respond to separate temperature or time demands. Zone design should maintain suitable flow and stable heat-source operation. Too many independently closing zones can be problematic for some systems.A practical exampleBedrooms may have different comfort requirements from the living room, within a coordinated control arrangement.Related termsThese are connected ideas, rather than always exact synonyms.Heating ControlsFlow Rate\">\n\t\t\t\t\t<details class=\"mwh-entry\"><summary><span class=\"mwh-entry-name\">Zoning<\/span><span class=\"mwh-entry-short\">Dividing a heating system into separate areas that can be controlled independently, improving comfort and efficiency.<\/span><span class=\"mwh-entry-prompt\">Read the explanation <span aria-hidden=\"true\">+<\/span><\/span><\/summary><div class=\"mwh-entry-body\"><p class=\"mwh-entry-lead\">Dividing a heating system into separate areas that can be controlled independently, improving comfort and efficiency.<\/p><h3>In more detail<\/h3><p>Allows different areas or circuits to respond to separate temperature or time demands. Zone design should maintain suitable flow and stable heat-source operation. Too many independently closing zones can be problematic for some systems.<\/p><div class=\"mwh-entry-example\"><h3>A practical example<\/h3><p>Bedrooms may have different comfort requirements from the living room, within a coordinated control arrangement.<\/p><\/div><nav class=\"mwh-entry-related\" aria-label=\"Related glossary terms\"><h3>Related terms<\/h3><p>These are connected ideas, rather than always exact synonyms.<\/p><div><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-heating-controls\" data-mwh-related=\"heating-controls\">Heating Controls<\/a><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-flow-rate\" data-mwh-related=\"flow-rate\">Flow Rate<\/a><\/div><\/nav><p class=\"mwh-entry-footer\"><a href=\"https:\/\/mywarmhome.co.uk\/stage\/glossary-2\/#mwh-glossary-zoning\" data-mwh-permalink>Link to this term<\/a><\/p><\/div><\/details>\n\t\t\t\t<\/article>\n\t\t\t<\/div><\/section>\t\t\t<\/div><div class=\"mwh-glossary__empty\" hidden><strong>No matching terms.<\/strong><p>Try a shorter word, another spelling or a different topic.<\/p><\/div>\n\t\t<\/section>\n\t\t\n<\/div>\n\n\n\n<div class=\"wp-block-group alignfull has-text-color has-background has-global-padding is-layout-constrained wp-container-core-group-is-layout-03f6d705 wp-block-group-is-layout-constrained\" style=\"color:#fffaf2;background-color:#134558;margin-top:0;margin-bottom:0;padding-top:clamp(48px,6vw,76px);padding-right:clamp(22px,5vw,80px);padding-bottom:clamp(48px,6vw,76px);padding-left:clamp(22px,5vw,80px)\">\n<h2 class=\"wp-block-heading has-text-align-center\" style=\"margin-top:0;margin-bottom:14px;font-size:clamp(30px,4vw,48px);font-weight:760;line-height:1.05\">Still sounds like jargon?<\/h2>\n\n\n\n<p class=\"has-text-align-center has-text-color wp-block-paragraph\" style=\"color:#ffffffd9;margin-bottom:0;font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.392), 18px);line-height:1.6\">That is useful feedback. The glossary should make retrofit easier to understand, not simply define one complicated phrase with another one.<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Plain English first Retrofit has enough acronyms already. Search a term, jump to a letter or choose a topic. Definitions are written for homeowners first, with the technical meaning kept intact. Look out for dotted terms around MyWarmHome. Hover with a mouse, tab to them with a keyboard, or tap on a phone for a [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"pagelayer_contact_templates":[],"_pagelayer_content":"","footnotes":""},"class_list":["post-4477","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/mywarmhome.co.uk\/stage\/wp-json\/wp\/v2\/pages\/4477","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mywarmhome.co.uk\/stage\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/mywarmhome.co.uk\/stage\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/mywarmhome.co.uk\/stage\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mywarmhome.co.uk\/stage\/wp-json\/wp\/v2\/comments?post=4477"}],"version-history":[{"count":5,"href":"https:\/\/mywarmhome.co.uk\/stage\/wp-json\/wp\/v2\/pages\/4477\/revisions"}],"predecessor-version":[{"id":4484,"href":"https:\/\/mywarmhome.co.uk\/stage\/wp-json\/wp\/v2\/pages\/4477\/revisions\/4484"}],"wp:attachment":[{"href":"https:\/\/mywarmhome.co.uk\/stage\/wp-json\/wp\/v2\/media?parent=4477"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}