{"id":4887,"date":"2026-09-27T08:55:38","date_gmt":"2026-09-27T08:55:38","guid":{"rendered":"https:\/\/mywarmhome.co.uk\/stage\/?page_id=4887"},"modified":"2026-10-01T20:24:11","modified_gmt":"2026-10-01T20:24:11","slug":"external-wall-insulation-2","status":"publish","type":"page","link":"https:\/\/mywarmhome.co.uk\/stage\/external-wall-insulation-2\/","title":{"rendered":"External Wall Insulation"},"content":{"rendered":"\n
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INSULATION \/ MY WARM HOME<\/p>\n\n\n\n

External wall insulation.<\/h1>\n\n\n\n

A continuous thermal wrap \u2014 planned around the whole building, not simply the insulation board.<\/p>\n<\/div>\n<\/div><\/div>\n\n\n\n

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01<\/p>\n\n\n\n

Understand<\/h3>\n\n\n\n

How EWI reduces heat loss and changes the wall.<\/p>\n<\/div>\n\n\n\n

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02<\/p>\n\n\n\n

Detail<\/h3>\n\n\n\n

Openings, services, moisture and thermal bridges.<\/p>\n<\/div>\n\n\n\n

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03<\/p>\n\n\n\n

Materials<\/h3>\n\n\n\n

Compare insulation and finishing systems.<\/p>\n<\/div>\n\n\n\n

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04<\/p>\n\n\n\n

Check<\/h3>\n\n\n\n

Assessment, installation and building safety.<\/p>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n

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THE SHORT VERSION<\/p>\n\n\n\n

EWI is a complete system, not just boards on a wall.<\/h2>\n<\/div>\n\n\n\n
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External wall insulation (EWI) adds an insulating layer to the outside of a property to slow heat loss, improve comfort and reduce energy needed to keep rooms warm.<\/p>\n\n\n\n

Insulation, fixings, reinforcement, weatherproof finish, openings, ventilation, services and moisture management have to form one coordinated design.<\/p>\n\n\n\n

The wall type, condition, exposure and occupancy matter. A solution that suits one home may not suit another.<\/p>\n\n\n\n

Questions to ask an installer \u2192<\/a><\/p>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n

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01 \/ UNDERSTAND THE SYSTEM<\/p>\n\n\n\n

Four things that determine a successful EWI project.<\/h2>\n\n\n\n

A continuous layer can help prevent heat escaping through poorly insulated external walls, particularly where the building has several exposed elevations.<\/p>\n\n\n\n

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01<\/p>\n\n\n\n

Wrap the building<\/h3>\n\n\n\n

The insulation layer should continue across the outside of suitable external walls to reduce heat loss.<\/p>\n<\/div>\n<\/div>\n\n\n\n

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02<\/p>\n\n\n\n

Detail the junctions<\/h3>\n\n\n\n

Windows, doors, eaves, corners, plinths and services need a carefully planned interface.<\/p>\n<\/div>\n<\/div>\n\n\n\n

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03<\/p>\n\n\n\n

Manage moisture<\/h3>\n\n\n\n

Consider the existing wall, exposure, damp, ventilation and the moisture behaviour of the proposed system.<\/p>\n<\/div>\n<\/div>\n\n\n\n

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04<\/p>\n\n\n\n

Design first<\/h3>\n\n\n\n

The chosen insulation and finish must suit the building, rather than being selected solely by thermal value.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n

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BEFORE WORK STARTS<\/p>\n\n\n\n

Health and safety comes first.<\/h2>\n<\/div>\n\n\n\n
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An installation affects the whole outside of the building. Assess existing services, wildlife, materials, access and safety before work begins.<\/p>\n\n\n\n

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Electrical services<\/h3>\n\n\n\n

High-amperage cables and external electrical supplies may require specialist consideration.<\/p>\n<\/div>\n\n\n\n

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Nesting and wildlife<\/h3>\n\n\n\n

Bats, bees, wasps and other protected or hazardous nesting situations may need specialist advice.<\/p>\n<\/div>\n\n\n\n

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Vermin and hazardous materials<\/h3>\n\n\n\n

Address rats, mice and squirrels before creating inaccessible voids. Arrange competent assessment of suspected asbestos in flues, drainage, roofing or other elements.<\/p>\n<\/div>\n\n\n\n

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Gas, flues and combustion<\/h3>\n\n\n\n

Do not compromise flues or combustion ventilation. Changes need checking by appropriately competent people.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n

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WHOLE-HOUSE THINKING<\/p>\n\n\n\n

Insulation and ventilation belong together.<\/h2>\n<\/div>\n\n\n\n
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Insulation and airtightness alter the way heat and air move through the property. The ventilation strategy therefore needs to be reviewed alongside the proposed EWI.<\/p>\n\n\n\n

Background and transfer air<\/h3>\n\n\n\n

Check whether suitable background ventilation is provided. Where needed, correctly sized trickle or wall vents and internal transfer routes such as door undercuts help air move between rooms.<\/p>\n\n\n\n

Extract ventilation<\/h3>\n\n\n\n

Kitchens, bathrooms, WCs and utility rooms require suitable extract. Existing fans should be checked against the relevant design or measured extract duty.<\/p>\n\n\n\n

An early design question<\/h3>\n\n\n\n

Do not improve the walls and forget the air. Moisture control involves insulation continuity, heating, background ventilation and extract working together.<\/p>\n\n\n\n

Explore the ventilation guide \u2192<\/a><\/p>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n

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02 \/ DETAILING MATTERS<\/p>\n\n\n\n

Thermal bridges can undo otherwise good insulation.<\/h2>\n\n\n\n

Thermal bridges are places where heat can bypass the insulating layer. EWI offers an opportunity to create continuity, provided the awkward junctions are designed.<\/p>\n\n\n\n

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01<\/p>\n\n\n\n

Reveals and openings<\/h3>\n\n\n\n

Window and door reveals, sills and frames need suitable insulation, weathering and sealing details.<\/p>\n<\/div>\n<\/div>\n\n\n\n

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02<\/p>\n\n\n\n

Roof and eaves<\/h3>\n\n\n\n

The new wall thickness must meet roof edges, verge and eaves without leaving exposed gaps.<\/p>\n<\/div>\n<\/div>\n\n\n\n

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03<\/p>\n\n\n\n

Plinth and ground<\/h3>\n\n\n\n

The DPC, splash zone and relationship to the ground require the correct product and detailing.<\/p>\n<\/div>\n<\/div>\n\n\n\n

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04<\/p>\n\n\n\n

Fixings and services<\/h3>\n\n\n\n

Fixtures and pipework need compatible extensions, thermal-break fixings or planned relocation.<\/p>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n

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\"Thermal\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Thermal continuity needs to be considered at every junction.<\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n
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\"Example
Poor detailing<\/figcaption><\/figure>\n<\/div>\n\n\n\n
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\"Example
Poor detailing<\/figcaption><\/figure>\n<\/div>\n\n\n\n
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\"Example
Good detailing<\/figcaption><\/figure>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n
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THE INSTALLATION<\/p>\n\n\n\n

How an EWI system is put together.<\/h2>\n<\/div>\n\n\n\n
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EWI is a set of compatible components installed to a complete specification. Product substitutions and improvised details need proper design approval.<\/p>\n\n\n\n

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01 \/ Assess and prepare<\/h3>\n\n\n\n

Examine the wall or substrate and complete the required repairs and preparation.<\/p>\n<\/div>\n\n\n\n

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02 \/ Fix insulation<\/h3>\n\n\n\n

Install the specified insulation boards using the system-approved adhesive and mechanical fixings.<\/p>\n<\/div>\n\n\n\n

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03 \/ Reinforce<\/h3>\n\n\n\n

Apply the designed base coat and reinforcement mesh.<\/p>\n<\/div>\n\n\n\n

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04 \/ Detail junctions<\/h3>\n\n\n\n

Finish openings, edges, corners, penetrations and roof or ground junctions correctly.<\/p>\n<\/div>\n\n\n\n

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05 \/ Protect the system<\/h3>\n\n\n\n

Apply compatible render, coating or cladding suitable for the property and exposure.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n

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DESIGN BEFORE PRODUCT<\/p>\n\n\n\n

Assess the building first. Select the system second.<\/h2>\n<\/div>\n\n\n\n
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A small modern flat and an older solid-wall family home will not respond to insulation in the same way. Construction, condition, exposure, moisture and how the property is used all affect the design.<\/p>\n\n\n\n

A competent assessment should cover these checks before a specification is finalised:<\/p>\n\n\n\n