A combi boiler provides both central heating and hot water directly from the mains, functioning much like a powerful, on-demand kettle.
In contrast, a system or regular boiler works by heating a larger volume of water that is stored in a separate hot water cylinder. This stored hot water can then be supplied to multiple outlets at the same time, for example, when more than one shower or taps are running simultaneously. While this setup provides a consistent flow of hot water to larger households, it does require additional space for the cylinder (and, in the case of a regular boiler, a cold-water storage tank too). As a result, system and regular boilers are generally more suited to homes with higher hot water demand and ample storage space.
System and regular boiler.
Usually natural gas or LPG. (can be electric, oil or biomass)
System and regular (or conventional) boilers are both heating systems with key differences in how they supply hot water and work with heating systems.
Here’s a breakdown:
System Boiler.
Components. System boilers have most of the essential components built-in, like the pump, diverter valves and expansion vessel, meaning they don’t need a separate tank to maintain water pressure. They do, however, require a hot water storage cylinder. Operation. System boilers heat water and then store it in a hot water cylinder, making it ready for when you require it. The built-in components make them relatively easier and quicker to install compared to regular boilers. Space. This setup requires less space than a regular boiler because there’s no need for a cold water tank in the loft. Efficiency. System boilers are energy-efficient and can provide hot water at multiple taps simultaneously, ideal for homes with more than one bathroom.
Regular (Conventional) Boiler.
Components. Regular boilers have fewer components within the unit itself. They require both a hot water cylinder (usually stored in an airing cupboard) and a cold water storage tank, typically located in the loft. Pumps and diverter valves are located externally and need to be designed correctly to prevent circulation problems. Operation. Cold water is stored in the loft tank, fed to the boiler, and then heated to supply hot water to the cylinder. This design may be more complex to install but can be better suited to homes with an older heating system that already has a water tank setup. Space. Requires more space overall, due to the need for both a cold water storage tank and a hot water cylinder. Efficiency. Regular boilers are reliable and can handle large volumes of hot water, ideal for larger homes. However, they may not be as energy-efficient due to heat losses from the cylinder and pipework, which should be fully insulated to improve the efficiency.
Handy notes. The hot water delivery rate for regular boilers is down to the head of pressure, this means how high up your cold water tank is, as this forces pressure down into the hot water tank. When water is drawn from the taps or shower, this will dictate the hot water flow (this can also depend on pipe diameters). Usually if you require a good power shower then stored hot water can usually supply.
The KW of system and regular boilers is down to the heating demand. Rule of thumb in the trade is treating each radiator as average 1.5kw, so 10 radiators would need a 15KW boiler! Then add 3kw for water heating.
A means of safely removing condensation from the boiler (soak away, drain etc). Condensate is acidic but not really dangerous (as acidic as lemon juice) but it can damage cement etc over time so it should terminate away from property walls.
External condensate pipework to be insulated with a class 0 insulation and off ground. Condensate pipes can freeze in the winter. Protection using a class 0 insulation (usually black and can be UV protective) prevents the insulation soaking up water and becoming a block of ice! Ideally the manufacturer will state size of condensate pipe to be used, if outside keep off ground and best practice is to terminate indoors. Condensate regulations here.
Benchmark to be competed by installer. This is in the manufacturer’s supplied service book. It needs to be filled in by the installer showing installers address, contact number, name, and business. It’s a tick box exercise to show the installer has signed off the installation. Flues should be at least 300 mm from openings into property (windows, doors etc). This is to stop products of combustion entering the property. A high level flue kit can be used in some circumstances to mitigate distance. Flues should be over 2m from ground. If not, then a flue guard is needed to protect from damage.
All combustion appliances must be installed by a competent person. Flues must be clear of openings to prevent products of combustion entering our dwellings. Below is a basic diagram showing flue clearances. Boiler manufacturer installation instructions will show correct clearances for each specific boiler and flueing arrangements (horizontal, vertical). The regulations sections has more information. Here is a link to a some Worcester literature which goes into more depth on flues.
Flue regulations.
All combustion appliances must be installed by a competent person. Flues must be clear of openings to prevent products of combustion entering our dwellings. Below is a basic diagram showing flue clearances. Boiler manufacturer installation instructions will show correct clearances for each specific boiler and flueing arrangements (horizontal, vertical). The regulations sections has more information.
Selecting a trustworthy installer for your heating, insulation, or renewable energy project requires careful research and due diligence.
Hiring the right professional ensures your home is safe, efficient, and compliant with regulations, and helps protect warranties, insurance, and grant eligibility.
Reputable installers are often accredited by recognised trade bodies or professional organisations. Accreditation confirms that the installer:
Meets industry standards
Has undergone proper training
Is legally authorised to perform specific types of work
NAPIT – Covers electrical and heating installations.
NICEIC – Approved contractor scheme for electrical work.
MCS – Microgeneration Certification Scheme – Required for heat pumps, solar PV, and renewable energy installations. Using accredited installers is essential for compliance, safety, and accessing grants or incentives, such as the UK Boiler Upgrade Scheme (BUS) or ECO4 funding.
Find a Qualified Retrofit Installer
Select the work you want carried out on your home.
This guide shows the qualifications, certifications and governing bodies
a competent installer should hold.
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Being registered with the above does not always mean the work is checked by the certification company, It usually shows competence within the field of current health & safety practices and current regulations. Remember that if you have any work carried out at your property either on a grant scheme or self financed you should be covered by consumer rights. The citizen’s advice is always a good place for information.
Some of the below will help with your journey in finding trades.
If you feel you are vulnerable.
Try to get a family member or neighbour to sit in with you when getting quote visits, also maybe designate someone else to deal with the process.
Ask for Recommendations.
Seek recommendations from friends, family, or colleagues who have recently had similar work done. Personal recommendations can be invaluable in finding trustworthy installers.
Read Reviews and Testimonials.
Check online reviews and testimonials on platforms like Trustpilot, Checkatrade, or Which? Trusted traders and google reviews. These platforms often provide insights into the quality of work and customer satisfaction, But please be aware that not all reviews can be genuine!
Obtain Multiple Quotes.
Don’t settle for the first installation company you find. Obtain quotes from multiple companies for comparison. Be wary of quotes that are significantly lower than others, as they may indicate subpar workmanship or the use of inferior materials. If you are applying down a grant funded route, then be weary of being promised the earth or pushed into signing up. Any decent installation company should keep you at ease and answer all your questions honestly.
Verify Insurance and Guarantees.
Ensure that the installation company/individual has adequate insurance coverage, including public liability insurance, to protect you and your property in case of accidents or damage. Also, inquire about any guarantees or warranties offered for the work they perform.
Check for Compliance with Regulations.
Certain types of work, such as electrical or gas installations, require compliance with specific regulations and safety standards. Verify that the installers you choose are appropriately qualified and registered to carry out such work.
Communicate Clearly.
Communicate your expectations clearly, including timelines, budget constraints, and any specific requirements you may have. Reputable installers will be transparent and be responsive to your needs.
Trust Your Instincts.
If something feels off during your interactions with installers or if they seem unwilling to provide necessary information or documentation, trust your instincts and consider looking elsewhere.
Get Everything in Writing.
Once you’ve decided on an installation company, make sure to get all agreements, including costs, timelines, replacement of fixings (window sills, skirting etc) redecorating and scope of work, in writing. This helps protect both parties and ensures clarity and accountability throughout the project.
External Wall Insulation can significantly change the look and function of your property, so it’s important to understand the process in detail before work begins. Confirm what insulation system will be used, its thickness, and the finish type (e.g. render, brick-slip, or cladding). Ask how the installers will deal with fixtures and features such as satellite dishes, alarm boxes, lights, air vents, overflow pipes, and external taps—these should all be properly removed, extended, and reinstated, not simply covered over.
Openings and Details.
Discuss how the system will accommodate windows, doors, and sills, as these may need to be extended or replaced to ensure proper sealing and to prevent water ingress. Check that drip beads, stop beads, and corner trims will be installed neatly and to specification for a high-quality, durable finish.
Ventilation and Airflow.
Make sure that ventilation and airbricks are not blocked or removed. Ask how they will be extended through the insulation system to maintain airflow and prevent damp or condensation. Obtain a clear ventilation specification, and ensure the finish matches or complements your property’s appearance. For homes with fireplaces or open flues, ask about spillage testing and combustion ventilation to ensure safety and compliance.
Groundworks and Damp-Proof Course.
Confirm that the insulation will finish above the damp-proof course (DPC) and that appropriate base trims and drainage channels will be installed. The system should not bridge the DPC unless designed to do so, as this can lead to moisture problems. Ensure that any existing damp or drainage issues—including blocked gutters or damaged downpipes—are addressed before insulation begins.
Aesthetics and Boundaries.
If your home is part of a terrace, semi-detached, or adjoins another property, ask how the system will terminate at party walls, fences, or neighbouring structures. Ensure that detailing will be neat and watertight. For listed buildings or properties in conservation areas, confirm that planning permission or building consent is in place. Regulations change so what may of been permitted last year may not be now, and visa versa!.
Safety and Compliance.
For homes with chimneys, fireplaces, or combustion appliances, ask about spillage tests and combustion ventilation to ensure safety after the installation.
Documentation and Clean-Up.
Request written details of all materials, fixings, and finishes, including manufacturer names and warranty information. Confirm that all waste and debris will be removed and agree on a timeline for completion and clean-up.
Finally, ensure you have full contact information for everyone involved in the project, including the installation team, project or site manager, and—if installed through a UK grant scheme, the Retrofit Coordinator responsible for oversight and compliance.
Internal Wall Insulation (IWI) and Room-in-Roof Considerations.
Disruption and Reinstatement.
Internal Wall Insulation can be highly disruptive, often requiring the removal of features such as skirting boards, window sills, coving, door frames, electrical sockets, light fittings, and radiators. Confirm that your installer will reinstate all removed items and specify whether they will be restored or replaced. Ensure that qualified tradespeople—such as joiners for woodwork and plumbers for wet work—will carry out these tasks, and get this commitment in writing.
System and Detailing.
Ask which insulation system will be used and how the installer plans to treat complex areas such as coving, cupboards, or meter locations. For room-in-roof spaces, confirm that any loft or eaves hatches will be properly insulated and professionally fitted, not simply boarded over. If you use roof storage, ensure this area remains accessible and structurally suitable for use once insulated.
Check that all electrical, alarm, TV, satellite, and internet cables will be correctly routed through the insulation and fully reinstated afterwards.
Ventilation and Safety.
A ventilation system should be installed as part of the works. Obtain a detailed specification to confirm it meets high standards of performance and finish. For homes with fireplaces or open flues, ask about spillage testing and combustion ventilation to ensure safety and compliance.
Pre-Installation Checks and Documentation.
Before work begins, inspect the external walls, damp-proof course, gutters, and downpipes. Any existing issues must be identified and either rectified by the installer or formally agreed with you in writing, as they can compromise insulation performance and cause long-term problems.
Finally, confirm that all debris will be cleared and agree on a timeline for completion and cleanup. Request full contact details for everyone involved, including the office manager, installation team (noting if subcontractors are used), and—if the work is part of a UK grant scheme—the Retrofit Coordinator overseeing the project.
Cavity Wall Insulation considerations.
Scope and Drilling.
Confirm that all suitable wall areas will be insulated, which may involve internal drilling. Discuss in advance where drilling will occur and what materials will be used to fill and finish the holes afterwards to ensure a neat appearance.
Garages and External Finishes.
For attached but unheated garages, talk through insulation options—particularly if shelving, cupboards, or other fixtures will need to be removed or adjusted. When drilling into external walls, ask what colour of mortar will be used to fill the holes, especially on rendered or painted surfaces. Confirm whether installers will repaint or touch up the finish to match the existing façade.
Material and Clean-Up.
Find out exactly which insulation material is being used and take the time to research its properties and suitability for your home. Clarify whether the installation team will be responsible for cleaning up spills, dust, or debris, and have this commitment documented in writing. If you have outdoor features such as ponds or livestock areas, inform the installers so they can take precautions against overspill.
Ventilation and Safety.
If new ventilation is required, request a clear specification and ensure all installations are completed to a high standard of finish. For homes with fireplaces or open flues, ask about spillage tests and combustion ventilation to maintain safety and compliance.
Pre-Installation Checks and Aftercare.
Inspect external walls, damp-proof courses, gutters, and downpipes before work begins. Any existing damp or drainage issues must be resolved first, as they can undermine the effectiveness of the insulation and lead to long-term problems. Finally, confirm that all debris will be removed and agree on a clear timeline for completion and cleanup—especially important for removal and refill projects.
It can be challenging to assess conditions beneath the floor unless you have a basement. Confirm the type, thickness, and support method of insulation being installed, and ensure all accessible areas will be covered. If floorboards need to be lifted, be aware this can cause damage—ask whether replacements will match the original boards to maintain appearance and consistency. Take pre-installation photographs for reference.
Cross Ventilation.
Adequate underfloor ventilation is essential. Make sure any existing vents or decorative grilles are retained or replaced with alternatives that are both functional and visually appropriate. Request written confirmation of how cross-flow ventilation will be maintained or improved, including details of the units being installed. The system should allow sufficient airflow to prevent moisture buildup and stop water ingress.
Basement Insulation.
If a basement is being insulated, ask about fire safety compliance and verify that all work adheres to current building regulations. It’s worth doing your own research for added assurance.
Ventilation and Safety.
If a ventilation system is included, obtain a detailed specification and confirm it will be installed to a high standard. For properties with fireplaces, request information on spillage tests and combustion ventilation to ensure safety and compliance.
Pre-Installation Checks and Cleanup.
Inspect external walls, damp-proof courses, subfloor ventilation, and rainwater systems (gutters, downpipes, etc.) before work begins. Any existing damp or drainage issues must be resolved first, as they could compromise the insulation and cause long-term damage. Finally, confirm that all debris and waste materials will be removed and agree on a clear timeline for completion and cleanup.
Ask which insulation materials will be used—such as spray foam, mineral wool, or PIR boards—and make sure you understand their limitations and how they may affect your property’s insurance or mortgage eligibility.
Access and Storage.
Discuss how the installation will impact access to essential services in the loft, such as boilers or solar inverters, and whether storage areas will still be usable or need adjustment.
Electrical Safety.
If you have recessed down lights, these must be properly protected to prevent air leakage and potential overheating. Suitable covers or fire-rated caps should be used. For electric showers or other circuits with cables running through the loft, ensure proof is provided that the cables are not buried within insulation, as this can cause overheating.
Pipework and Loft Hatches.
All exposed water pipes should be fully insulated. The loft hatch should also be insulated and drought-proofed to a professional standard—avoid makeshift solutions like loosely stapled insulation.
Ventilation and Timber Protection.
Adequate airflow in the loft is essential to prevent condensation and protect the roof timbers. Confirm that ventilation will be maintained or improved as part of the work.
Whole-Home Ventilation and Safety.
If a new ventilation system is being installed, request a clear specification to ensure it meets high-quality standards and finishes. For homes with open fireplaces, ask about spillage tests and combustion ventilation to ensure safety and compliance.
Most combination boilers need a larger gas supply pipe than older systems, often requiring an upgrade from the meter. Before installation, confirm the planned gas pipe route to avoid unnecessary external runs if an internal route is possible. If the pipe must run outside, ensure it’s properly clipped and installed in line with regulations.
Heating Controls.
Discuss your heating controls and where the thermostat will be located. It should be positioned in a room without a thermostatic radiator valve (TRV) or any secondary heat source such as a fire or cooker, to ensure accurate temperature readings.
Condensate Drainage.
All condensing boilers produce condensate that must be drained safely. Ideally, this drainage point should be located indoors. If the condensate pipe must run externally, it needs to be insulated with Class 0 lagging. Confirm the type of insulation being used and how it will be secured and supported.
System Clean and Preparation.
Ensure all debris will be removed during installation and clarify when this will happen. Most boiler manufacturers require a full system flush before fitting the new unit—this is essential. Make sure the installer carries it out, and ideally, observe the process. The correct use of cleaning and inhibitor chemicals is vital for system health, and their use should be recorded in the Benchmark log (the boiler’s installation and service record). Ask for a copy for your files.
Warranty and Guarantees.
Confirm both the manufacturer’s warranty and the installer’s guarantee, particularly regarding leaks and workmanship. Once the boiler is installed, it’s a good idea to call the manufacturer directly after a few weeks to confirm that your warranty is fully registered and active.
You may already know the direction your property faces, but installers might suggest positioning the panels differently. This could be due to access issues, roof condition, or other practical constraints. However, the optimum orientation delivers the best performance, so make sure your installer prioritises efficiency over convenience.
Inverter Location.
The inverter should be installed somewhere easy to access for inspection, servicing, and maintenance, while also being protected from the elements. Some models are suitable for outdoor installation, provided they’re shielded from direct sunlight and rain. If you live near the coast, ask about corrosion resistance and whether additional protection is needed.
Monitoring Meter.
The generation meter (monitoring meter) should be positioned where it can be easily read and checked regularly. Make sure it’s visible enough to monitor energy production and detect early signs of faults (for example, if it isn’t blinking in daylight). Some installers may say it has to go in loft if inverter is also installed there, but dont allow, have it somewhere you can read and check.
Paperwork and Certification.
Confirm the expected timescales for all necessary documentation, including MCS certification, DNO approval, and any paperwork your energy supplier may require.
Warranties and Guarantees.
Clarify the warranty terms and guarantee lengths for all equipment. Make sure you know who to contact in case of faults or system failure.
Get Everything in Writing.
Once you’ve decided on a installation company, make sure to get all agreements, including costs, timelines, and scope of works, in writing. This helps protect both parties and ensures clarity and accountability throughout the project.
Ask your installer to explain which make, model of heat pump is being fitted and why it’s suitable for your property. Confirm that the system has been properly sized for your home, an undersized or oversized unit can reduce efficiency and increase running costs. Request a full design calculation (MCS or equivalent) showing heat loss per room, flow temperatures, and emitter sizing. Ask what refrigirant is used within the pump (R32, R290 etc). Ask about hybrid systems to help in the winter months.
Outdoor Unit Location.
The external unit should be positioned where airflow is unrestricted, but noise and vibration will not affect you or neighbours. It must sit on a stable, level base (often a concrete pad with anti-vibration plinth) and be clear of obstructions such as fences or foliage. If located near boundaries, confirm it meets local noise regulations and planning guidance. It should meet manufactures clearances for optimum airflow. For coastal or exposed locations, ask about corrosion-resistant finishes and protective coatings. (if within 2000m from the coast this is a must)
Internal Components.
Confirm where the indoor cylinder, buffer tank, and controls will be located. These should be easily accessible for servicing and maintenance, with pipework neatly installed and insulated. Discuss how existing systems—such as radiators or underfloor heating will be adapted or replaced, and ensure the flow and return pipe sizes are appropriate for the new system.
Condensate and Drainage.
Heat pumps produce condensate water, particularly in colder weather. This must be drained safely away from the base unit, ideally into a proper soakaway or drain. The pipework must not freeze, so confirm that suitable insulation and gradients are in place. The condensate produced is not the same a a combustion boiler so it is not acidic.
Electrical and Controls.
Ensure the electrical supply is adequate and compliant with regulations, with a dedicated isolator switch. Ask about the control system whether it will use smart thermostats, weather compensation, or load compensation and how to use these features for maximum efficiency.
Groundworks and Protection.
If installing a ground source heat pump, confirm the ground loop layout (horizontal trenches or boreholes), and request documentation of where pipes are buried for future reference. For air source units, confirm that rainwater runoff from roofs won’t drip onto the unit and that the area around the base remains well-drained and clear of standing water.
Warranties, Maintenance, and Support.
Ask for details of warranties and service agreements for both the equipment and installation. Heat pumps require annual servicing to maintain performance and warranty validity, so ensure you receive a maintenance schedule and the installer’s or manufacturer’s contact details.
Paperwork and Certification.
Ensure you receive all necessary documentation, including MCS certificates,DNO notifications, and user manuals. These are essential for warranty registration, grant schemes (such as the Boiler Upgrade Scheme), and resale value.
Cleanup and Completion.
Confirm that all debris and packaging will be removed and agree on a clear completion timeline. Obtain written contact details for the installation company, lead installer, and if installed through a UK grant scheme the Retrofit Coordinator responsible for the project.
Improving your EPC rating isn’t just a “box-ticking exercise” it brings real financial, comfort, legal, and long-term benefits.
Improving your EPC rating isn’t just a “box-ticking exercise” — it brings real financial, comfort, legal, and long-term benefits. It matters because, as we progress through life, our habits, and priorities tend to shift. The carefree 20-year-old who stayed up all night and partied eventually becomes someone more conscious of energy use, the environment, and personal finances. Taking small steps to look after both the planet and our own future becomes part of that natural transition. Its not only landlords and developers who are being targeted to improve energy performance of where we live but it surly come to all of us as regulations tighten.
Improving an EPC (Energy Performance Certificate) rating usually means reducing heat loss, increasing efficiency of heating systems, and incorporating low-carbon technologies. Here’s a clear, practical list of the most effective ways to improve an EPC rating in UK homes: If you NEED to improve the EPC for rental or other purposes then I would always suggest getting a qualified and experienced DEA or Retrofit assessor to perform a Pre EPC to highlight the improvements (modelling).
1. Improve Insulation (Biggest, most cost-effective wins)
Can be applied to suspended timber floors and solid floors
Reduces draughts and cold spots. Sometimes the installation method can be in a very small crawlspace.
Draught-proofing.
Low-cost, fast EPC improvement that can easily be done on a DIY level.
2. Upgrade Heating Systems.
Replace the old gas boiler with a modern condensing boiler.
Increases efficiency to 90%+. This will be getting phased out as the UK moves away from gas boilers. Each elected government always changes the goal posts, so it’s always checking current legislation if replacing a fossil fuel heating source.
Modern cylinders have better insulation and can hold the temperature of stored water for longer periods.
Replace with a heat battery, which removes standby losses and improves SAP scores (great with heat pumps and Solar)
4. Replace Windows & Doors.
Replacing old windows, especially wooden single glazed, to a more modern double/triple glazed unit can improve the EPC and also add value to the property through aesthetics and performance. Double and triple glazing can be very little difference on a EPC. You can usually tell the age of your glazing by looking for a date in the double-glazed gap or by the gap its self. Typically, the larger the gap, the newer the glazing. A good quality unit will typically have date stamped in the gap!
The light energy frees electrons, creating a Direct Current (DC) flow of electricity.
A photovoltaic system consists of PV cells, which are grouped into modules (solar panels) and arranged into arrays.
They contain cells, usually made of silicon, that release electrons when hit by sunlight, creating a flow of electricity. An inverter converts this power into the standard electricity used for appliances, helping lower energy bills
Solar PV basics.
Solar panels provide an eco-friendly and sustainable method for power generation, as they harness sunlight and produce no direct greenhouse gas emissions during use. They are utilized globally to lower electricity costs, reduce dependence on fossil fuels, and minimize the carbon footprint associated with energy production.
Over the past 20 years, solar power has seen significant advancements in both affordability and technology, including improved energy transfer and storage capabilities. For solar energy to be truly beneficial in the UK, it is essential to either store the generated energy using batteries or feed the excess power back into the grid through energy providers.The system gathers that heat, boosts it, and releases it indoors.
Sunlight (photons) hits the solar panel cells, which are made of special materials (semiconductors).
Different types of solar panels.
Solar PV (Photovoltaics). This is the technology that converts sunlight directly into electricity using photovoltaic cells. These cells are typically made from semiconductor materials, such as silicon, which absorb photons from sunlight and release electrons. This flow of electrons generates direct current (DC) electricity, which can be converted to alternating current (AC) using an inverter for use in homes. Solar PV systems can vary in scale from small residential rooftop installations to large solar farms. They are a key component of renewable energy strategies, helping to reduce reliance on fossil fuels and decrease greenhouse gas emissions.
Solar thermal. This is the technology that harnesses sunlight to produce heat, which can be used directly for heating our water, it can be used commercially to generate steam for industry, but we are looking at domestic systems here. Solar thermal technology is valued for its efficiency in directly using the sun’s energy for heating applications, contributing to lower energy bills and reduced reliance on conventional fuel sources. The panels used either have a dark absorbing surface made from polymers or evacuated tubes which look like fluorescent tubes. The evacuated tubes are more efficient in cold climates but can overheat if too hot.
For any renewable heating or solar project, whether funded privately or through a UK grant scheme, the current best practices, manufacturer’s instructions and relevant building regulations should be strictly adhered to. If installed on a UK grant scheme then a quality assurance program that certifies small-scale renewable energy systems and installers need to be followed, currently this is supplied by MCS.
It is also advised to use MCS installers to mitigate any problems with planning and safety compliance.
Other companies like the IAA offer microgeneration guarantees too. Most of the time when applying for renewable funding the installation company usually has the mechanism to set up the funding and this should be explained from the start.
You should NOT have to pay anything upfront or post install unless extras are quoted and agreed.
These extras could be, for instance, extra panels, battery connected inverter’s, batteries and possibly EV chargers. Get your installers to confirm the process of connecting to your grid supply, which is detailed below.
Currently, there are various funding streams, but are typically means tested. Have a look at the funding area of the site for more information.
To achieve effective solar panel installation in line with best practices, MCS standards, and building regulations, please review the following installation and operation guidelines.
DC LabelGround ArrayRoof Array
Pre-install.
Before connecting a solar power system, you must submit a DNO application to the relevant distribution network operator. This ensures they can assess and manage the required *electricity capacity. The documentation needed depends on the system’s size, larger systems generally require more paperwork before installation. For solar power systems, the standard threshold is 16 amps per phase, determined by the inverter’s AC output. If you’re unsure of the amp rating, consult the installation company’s electricians for guidance.
Labels/shut offInverter ErrorSchematic Diagram
*Electrical capacity, measured in amps (amperage), is the maximum amount of electricity a circuit can handle, so the DNO needs to make sure the generated power can be pushed back down the cables safely!
“phase” refers to the distribution of electrical load within a circuit, with “single phase” meaning there’s only one live wire supplying power to a household. Most UK homes are single phase.
Systems with an AC output under 16 amps per phase (less than 3.68kw) can be registered with a G98 form, usually allowing immediate installation. Systems exceeding 16 amps per phase (more than 3.68kw)are classified as large and require prior approval and a G99 form from the DNO before installation.
Informing your supplier.
If you’re trying to set up a Smart Export Guarantee with a supplier, they will require documentation like a DNO letter, they may also want a G98 or G99 approval and MCS certificate, They will require an export MPAN (they can usually request this from your DNO). Email your electricity supplier to inform them of the solar installation, give them the exact date of installation even if you have not received your MCS or other documentation. They will then confirm in return and hopefully guide you with the process.
What is an export MPAN? An export Meter Point Administrator Number (MPAN) is an industry reference for a unique 12 or 13-digit reference number to identify where electricity is fed into the grid. It helps to ensure exported electricity is measured accurately and payments/credits owed are assigned to the correct account. This can take your supplier many weeks to retrieve from your DNO. This number is different from your standard MPAN 21-digit number on your bill. We have a section in the blog to explain more. More details here.
Post-install.
All DC and AC solar cables and isolators Should be labelled throughout the installation. This is a MCS guideline, which we know is not a regulation, but any good installer should complete all the tasks mentioned. Ask the installers if your supplier is being informed. The installers may inform your supplier and pass on the necessary documentation but personally contact your energy supplier by email to confirm. PV cables under the panels. These should be secured, so the wiring is not touching the roof. This is to prevent failure, snagging and build up of debris. Safe lockable isolation at inverter. DC (black) and AC (red) Correct fixing of inverter. Manufactures will state surface mount requirements (fireproof etc). Clear diagrams of system to be placed near inverter (schematic diagram). This shows the setup of the system for maintenance and electrical circuits. Solar on roof label to be close to main fuse. This is mainly to inform emergency services that DC exists on the roof. Monitor meter. Should be installed in a location for ease of access and allow the occupier to be able to monitor the system to check for generation and faults (can be installed into consumer unit). The generation meter light should be blinking in the daylight, if not could be failure, check for warning on inverter. Some inverters are remotely monitored for failure, this should be explained and monitoring contact information left on site. Check that your meter is suitable for selling on excess energy. This usually has to be a smart meter and your energy supplier can guide you. Panel position. Solar panels should be installed to optimize daylight and eliminate shading, this is typically at a 35° angle facing south. Panels should not extend more than 200 mm from the roof surface and be minimum 400mm from the edge to prevent uplift, latest regulations, MCS guidance and manufacturer installation information should be followed. Flat roofs and pitched roofs have different installation techniques and parameters. Solar wizard, a good place to start to check orientation. Panel Type. Ask what configuration panels are. They could be in series or parallel. Protection. Panels may need to be protected from nesting birds or vermin. Labels. Cables should be labelled with DC warnings, and this should ideally be visible on each internal and external run. All meters and isolation switches should be labelled. Ground Panels. If panels are ground mounted, then cables to inverters should be safely and securely routed and labelled. Typically, in ground trenches at a minimum 500 mm. Ground mounted panels should be secured to prevent wind lift. Weighted and secured. Earth wires (bonding). Should be fitted to gas meters and water stopcocks. To prevent any electrical current moving to uninsulated pipework in case of failure or damage to the system. Planning permission. Typically, not required for domestic solar panel installations. However, planning permission may be required for listed buildings and conservation areas. If using an MCS registered installer, this should be verified for you.
Generation MeterGeneration MeterEarth Bonding
Series or Parallel.
Series connection.
Increases voltage, but keeps amperage the same
Suitable for high-voltage applications
Optimal output at the beginning and end of the day
Easier to work on, and requires less expensive wire
Sensitive to shading
A disruption in a series connection affects the entire system
Parallel connection.
Increases amperage, but keeps voltage the same
Suitable for systems with high current requirements
Better shading tolerance
Panels continue to work independently of each other
May require larger cables and additional equipment
May increase upfront costs for materials and installation
Micro InverterHybrid InverterInverter
Batteries.
Solar batteries store the extra electricity generated by solar panels, much like how car batteries hold the charge produced by alternators. These batteries allow homeowners to keep surplus energy for later use, increasing energy independence and reliability. They can power household appliances and charge electric vehicles, providing a convenient and sustainable energy solution. Batteries come in different sizes and make-ups. The most popular are lithium-ion, which uses lithium mined from countries like Argentina and Brazil. These batteries have a longer lifespan, store more power in a smaller space and are very efficient.
Tesla PowerwallEddi Power DiverterBattery and Inverter
Lead-acid batteries can be used, but due to size and poor efficiency, we don’t really see them now on UK systems. A new kid on the block is the saltwater batteries, which are an eco-friendly option but have lower power density compared to chemical batteries.
Benefits. When your solar panels produce more electricity than your home or building needs, the excess energy flows into the solar battery instead of being sent back to the grid. This stored energy can be drawn upon when the panels aren’t generating enough power. While the initial cost of solar batteries can be high, they can offer long-term savings by reducing the need to buy electricity from the grid, making them a worthwhile investment if within budget.
Solar battery systems are usually paired with hybrid inverters, which manage the flow of energy between the solar panels, batteries, and the grid. While initially more costly, they offer significant long-term savings and resilience, particularly valuable in areas prone to outages or with fluctuating energy cost.
Under the new P63100 standard regarding battery location, the basic premise is that the best place for storage batteries is outside the dwellings and away from habitable rooms. Where it is not practicable to locate batteries outdoors, some basic requirements are provided in P63100. Batteries shall not be installed in any of the following locations:
rooms in which persons are intended to sleep
routes used as a means of escape that are not defined as protected escape routes including landings, staircases, and corridors
corridors, shafts, stairs, or lobbies or protected escape routes
firefighting lobbies or staircases
storage cupboards, enclosures, or spaces opening into rooms which persons are intended to sleep;
outdoors within 1m of escape routes, doors, windows, or ventilation ports
voids, roof spaces or lofts
within 2m of stored flammable materials and fuel storage tanks or cylinders; and
cellars or basements that have no access to the outside of the building
Any battery storage in a place that is visited infrequently, then a fire alarm shall be installed to satisfy current regulations or standards.
Power diverters.
A power diverter is a device used in solar energy systems to redirect surplus electricity generated by solar panels to power specific appliances in your home, rather than sending it back to the grid. This allows you use of the solar power you generate by directing it to energy-intensive devices.
How it works. When your solar panels produce more electricity than your home is currently using, the power diverter detects this excess energy and automatically redirects it to a designated appliance (most commonly an immersion heater for hot water).
This prevents surplus energy from being exported to the grid, where compensation rates can be lower than the cost of grid electricity. Power diverters are usually affordable and easy to install compared to batteries, making them a popular choice for homeowners who want to improve their solar energy efficiency without a large upfront investment like batteries.
Heat is collected from outside (air, ground, or water).
That heat is compressed to raise its temperature.
The warmed heat is delivered to radiators, underfloor heating, blower units, or hot water.
The cycle repeats, quietly and continuously.
Electrical certificates.
The two types of electrical certificates you will come across as a customer who is having any electrical work as part of installing EEM’s (energy efficient measures)
Electrical Installation.
Minor Works Certificate.
Electrical Installation Certificate.
An electrical installation certificate is the type of certificate a customer receives after an electrician has installed one or more new circuits. Other examples include a complete rewire, a replacement consumer unit or an additional consumer unit. Generally, any time electrical work is done at the consumer unit, a new installation certificate will be issued.
Minor Works Certificate.
A minor works certificate is issued after an electrician has made an alteration to an existing circuit. Minor works certificates are often used to certify work such as adding additional sockets to an existing circuit or increasing the number of light fittings in a room. It can also be where a fused spur has been installed for an appliance or boiler connection.
You may need specialist advice from tradespeople and professionals regarding things like, Nesting. Bees, wasps, bats. Vermin. Rats, mice, squirrels Asbestos. Flues, guttering, facia boards etc. If squirrels, rats, or pigeons etc have the potential to nest or shelter under panels then protection will be required. Not only can they damage the panels, but they also tend to gnaw and pull on cables.
Some older houses may contain asbestos, which only a trained eye can recognise. Never disturb anything you’re unsure about. The health and safety section has more details.
Your property will have ladders and possibly scaffolding during installation of solar panels so it’s crucial for safety guidelines to be in place, warning signs, pavement ramps etc. Contractors should always explain the dangers and inform you of any changes. If you have close neighbours, then permissions may be needed for access and also approval for works in regard to noise and nuisance during installation (always polite anyway). Gas appliances and ventilation requirements should be carefully considered during the work, especially vertical flues and tile vents for loft ventilation.
Store or use, the supplier will pay less for the power return.
Having solar panels on our properties allows us to generate electricity when the British weather cooperates, of course! How we use that electricity depends on our needs and what we can afford to optimize. While batteries are an excellent way to store and use solar energy efficiently, they can be expensive, making them inaccessible to many.
For those without battery storage, making the most of solar energy means using appliances at the right time or selling excess electricity back to the grid. For example, if we generate 1.6 kW per hour on a sunny day and run a 1.4 kW washing machine, we get a free wash, avoiding the import cost of around 34p per kWh. If we don’t use the energy and instead sell it back via the Smart Export Guarantee (SEG), we might only receive 15p per kWh. That means using our own power saves us 19p per kWh. Since it’s not always feasible to perfectly match generation and usage, finding the right balance between importing and exporting electricity is key to maximizing savings and efficiency.
A heat battery is a device that stores heat energy and releases it when your home needs it.
As the UK moves towards cleaner and smarter ways to heat our homes, one technology is starting to make a name for itself: heat batteries.
You might have seen them mentioned alongside heat pumps in recent government home upgrade plans. But what exactly are they, and why are they becoming popular?
You’ve probably heard of old type electric storage heaters maybe you’ve even come across one before. They store heat inside metal cabinets using heavy bricks, using cheaper electricity at night when most people were asleep and demand was low.
Heat batteries work on a similar idea, but with modern materials and smarter design. They store energy as heat when electricity is cheaper or more available, and then release it later when you need hot water or heating. Below is a video from sunamp.Heating battery basics.
So what is a heat battery?.
A heat battery is a device that stores heat energy and releases it when your home needs it. Think of it as a modern alternative to a hot water cylinder, but smaller, faster, and far more efficient.
Instead of storing litres of hot water, a heat battery stores energy using materials like phase-change materials (PCMs) or ceramic blocks. These absorb and hold heat at high temperatures, then release it on demand to heat water or contribute to space heating.
How Does a Heat Battery Work?
A heat battery typically works in three simple steps:
Charge.
The battery is heated using electricity from your heat pump, solar PV, or the grid — often at off-peak times when energy is cheaper and cleaner.
Store.
The system holds that heat with minimal loss, often for many hours. Phase-change batteries “lock in” heat as they melt and solidify, similar to how ice packs work — just at much higher temperatures.
Delivery.
When you open a tap or your heating system calls for hot water, the battery releases stored heat instantly. You get quick, consistent hot water without waiting for a tank to warm up.
Why Are Heat Batteries Becoming Popular?
Smaller Footprint.
A heat battery can be up to 5–10 times smaller than a traditional hot-water cylinder. Great for flats, small homes, or anywhere space is tight.
Faster Recovery
They recharge quickly, making them ideal for busy households needing lots of hot water.
Works well With Heat Pumps.
Heat pumps run best at steady, low-demand times. Heat batteries let you store heat produced overnight or when your heat pump is running efficiently.
Perfect with Solar Panels.
Solar PV can charge the battery during the day, giving you almost-free hot water in the evening.
Lower Bills with Smart Charging.
Pairing a heat battery with:
off-peak tariffs
smart meters
solar generation can significantly cut running costs.
What Can a Heat Battery Replace?
In many homes, a heat battery can replace:
Traditional hot water cylinder
An immersion heater
In some setups, parts of a boiler system
They are particularly useful in heat-pump-only homes or homes switching to low-carbon heating.
Are They Eligible for Grants?
Yes, the government recently confirmed that heat batteries now qualify for a £2,500 grant under the Boiler Upgrade Scheme. This brings their upfront cost down significantly and makes them competitive with traditional hot-water systems.
Should You Install One?
A heat battery is ideal if:
You have (or plan to install) a heat pump
You want to save space
You’re looking to manage energy costs using solar PV or off-peak tariffs
Your home has high hot-water demand
You want a future-proofed, low-maintenance system
You need to improve a EPC rating on a property using old storage types.
They’re less suited to very large households with extreme hot-water usage — a large cylinder may still be a better fit in those cases.
Final Thoughts.
Heat batteries are one of the most exciting upgrades currently available for UK homes. They’re compact, efficient, low carbon, and cost-effective — and with the new grant support, they’re more accessible than ever.
A Publicly Available Specification (PAS) is a document that defines good practice standards for a product, service, or process. PAS 2035/2030 are linked frameworks that outline best practices for retrofitting homes in the UK to enhance energy efficiency. While PAS 2030 focuses on the quality of the installation processes, PAS 2035 ensures that the retrofit is appropriate for the building as a whole. Current PAS documents can be downloaded here. It’s a crucial component of the UK government’s strategy to boost building efficiency and reduce carbon emissions. Adopting a “whole house” approach, PAS 2035 considers the home’s environment, occupancy, and the homeowner’s objectives, ensuring that retrofit projects address key aspects such as insulation, ventilation, occupancy, and building fabric to support long-term sustainability. Although not a regulation, PAS 2035 is a publicly available specification (PAS), developed to address shortcomings of previous schemes following the Each Home Counts Review.
PAS 2035 compliance is mandatory for all publicly funded projects, including those supported by the Energy Company Obligation (ECO), and Warm Home Fund. We also have a route called licence plus which is run by Trustmark which does not need coordination as part of its process!. This is mainly aimed at self funding retrofit but using installers that are roughly following the current PAS process. Whichever mechanism is to be used, the property occupier should request details of which route the process follows pre-install.
PAS 2035 has its strengths, but also notable limitations. If everyone in the supply chain, assessors, coordinators, designers, and installers adheres strictly to the process, the framework should work effectively. However, lapses in monitoring and inspection can lead to issues. Unfortunately, “technical monitoring” for most UK schemes is minimal, and no longer performed by Ofgem, meaning that failings can go unnoticed, leaving property occupiers unaware of potential problems. Hopefully this will change with future consultations.
The retrofit process involves a range of participants, including canvassers, lead generators, social marketeers, assessors, designers, coordinators, installers, and a limited number of technical monitoring agents. This complexity, along with regulations, updates to rules and red tape, can create confusion and drive up costs.
The standard will transition from PAS 2035:2019 to PAS 2035:2023 in March 2025.
Protecting the Property Occupier?
PAS 2035 outlines several requirements for both pre- and post-installation stages. One of its most valuable aspects is the involvement of a retrofit coordinator throughout the process. The coordinator’s primary role is to safeguard the interests of the property and its occupants, ensuring the retrofit is carried out effectively and sustainably. In an ideal scenario, the retrofit coordinator would operate independently, free from any conflicts of interest. However, this level of impartiality is often difficult to achieve in practice.
By understanding the processes outlined below, you’ll hopefully gain the knowledge needed to ask informed questions and engage with some confidence at various stages of your retrofit journey.
Successful retrofit process.
Social housing and councils may have their own ways of engagement, with separate routes for ECO funding. Within this sector, retrofit is usually done en-mass and with consultation with tenants and housing officers. The below is assuming you are not a social housing or council tenant, but the PAS should still be followed within these organisations to protect the property and the occupiers.
It will all start with a knock on the door, a social media campaign, a referral, or housing provider intervention (landlord). You may be offered funded insulation or heating upgrades, sometimes windows and doors. You may fill a form in from an advertised link you have followed, or you may enquire to see if you qualify from a canvasser.
This information is typically passed on to the installation companies (lead generation) or the installation companies are involved in the marketing campaign directly.
It’s always exciting to get something for free! However, while promises may seem grand, it’s important to remember that you are entering into a works contract with the installation company. To ensure you get what was offered, make sure everything aligns with current regulations, OFGEM guidance, and the latest PAS standards.
In practice.
If the property / occupants have met the requirements of a funded scheme, then the installation or funding company will arrange for a retrofit coordinator to instruct a visit from a retrofit assessor. The coordinator is the first in the process as this is the stage that the property classification is usually identified (traditional, non-traditional etc.)
The assessor should try to get a picture of what the typical energy use entails and also what is expected by improving the property. Lots of photographs will be taken as an EPR (energy performance report) will be produced at the end. This is basically a reference EPC (energy performance certificate) but does not get published on the central register. (when EEM work is completed, a new EPC should be produced, ideally the original assessor as they will have the original data)
Some quick guidance on what the assessment entails and why!
First things are age and condition. This is to allow a retrofit coordinator to classify the property and create a plan that allows a fabric first approach that works with the natural balance of the property and highlights all potential issues.
Existing Ventilation in wet rooms photographed and noted. This is because all insulation packages require moisture to be controlled post installation. Some insulation situations require upgrades due to the design and current regulations.
Existing background ventilation photographed and noted. This is because all insulation packages require the replenishment of air post installation. Some insulation situations require upgrades due to the design and current regulations. Installers may use a pulse or blower test may be performed to validate if upgrades to background ventilation are necessary.
Fuel burning appliances noted. This is especially relevant with open flued appliances like gas, wood/coal burning fires etc. Ventilation requirements for combustion may need to be installed or verified adequate.
Whole footprint of property measured, including all windows/glazed doors. This allows to distinguish what is a “heat loss area” in more detail, and also potential solar gains.
Plenty of images of outside. This is to show the condition of building elements, including damp course and drainage services (gutters, downpipes, soil pipes).
Access to all rooms are required as is the loft space, basements and visual inspections of all external walls and areas. All ventilation present will be recorded and door undercut measurements should be taken. The assessment can take longer if more than one installation is being carried out, i.e. wall insulation, loft, and heating.
A report is then generated to give a rating of the properties’ energy performance from “A (very good) to a (G) very poor”. Information is then made available to the retrofit coordinator. All data is uploaded to the *Trustmark data warehouse, which forms a property plan and can be accessed by involved parties.
The coordinator will then look at all the data to see if improvements need any special design attention and intervention due to condition, age of property and location. If all looks OK then a ventilation strategy will be put in place depending on installation requirements. Some other documents are required, like a medium term improvement plan, which will create future scenario’s for improvements.
A retrofit designer will need to be consulted to design the proposed installation measure(s) if deemed necessary. We can take designers of certain measures as being members of a trade body. For example, a Gas Safe engineer installing a gas boiler, a SWIP trained installer performing IWI to a traditional non-heritage building, MCS accredited installer for solar and heat pumps.
A professional member of a Chartered Institute will be required, especially on buildings with heritage values or interacting insulation systems (wall and floor insulation being installed together, for example). It is up to the retrofit coordinator to validate that the designers and installers are all suitably qualified.
* The TrustMark Data Warehouse was created to address several recommendations in the Each Home Counts review commissioned by the Government in 2015.
The retrofit plan is executed. This is what the installers are expected to perform to meet the current PAS. Each measure (installation or improvement) will have its own route and requirements, and brief information be found on each section within this site. The plan will provide steps for the current and potentially future improvements. A fabric first approach is always used, this means insulation before any heating works need to be carried out. Soft touches should also be part of the fabric first approach like heating controls, draught proofing and low energy lighting.
The occupants should be informed of all work. It should be the co-ordinator and installers who contact the occupiers to inform them of the process that the retrofit project will follow. Dates, times, and conditions required will need to be discussed and agreed upon. This may include removal of furniture to prevent damage or the arrangement of alternative living arrangements throughout the works (especially on internal wall insulation). It may include preinstall remedial works to the property structure or minor repairs like broken windows, failing of rainwater removal (poor guttering) and wall pointing.
Get all this information in writing or in an email to reference at a later date if required. Make notes of Installers contact details, coordinators, and assessors names and numbers. This can be invaluable if you need to contact anyone involved in the process. You can do research on installers, co-ordinators, assessors and designers here as they all need to be Trustmark registered.
The Installation.
Once agreed and a plan has been discussed, the installation will begin. If an insulation measure is being installed, then validation is required that either the current ventilation is sufficient or insufficient. The assessment would have highlighted any shortfalls, and the installers may ask to perform an air tightness test. This can be carried out using a pulse test, this may be performed to allow installers a way of emitting undercuts and background ventilation from the installation, but controlled ventilation is always a good way to control moisture. The ventilation should always be installed or upgraded first, or at least core vents and wiring set in place if wall insulation being installed. The *retrofit coordinator should make a site visit if the measure is deemed high risk which includes IWI, EWI, UFI, FRI, PHI and RIR. (*this will be a mandatory requirement from early 2025) The next stage will be the installation phase of the main improvements.
*Due to time and location factors, the retrofit co-ordinator may employ a remote coordinator to feedback information after or during site visit.
The Handover.
Depending on the complexity of the installation, the duration can range from a single day to several weeks. This timeline should have been discussed and documented during the early planning stages. Before signing off on the work completed by the installation company, ensure you are fully satisfied that all agreed tasks have been completed to your expectations. Additionally, verify that any damages have been repaired or compensated. Make sure you have received all necessary handover documents, including warranties, guarantees, compliance certificates, insurance policies, gas certificates, and electrical certificates. Some certificates and warranties may come via post or email after the installation, if this is the case then ask for written clarification that they will be provided. All these documents are part of the works and may be needed if selling the property or for insurance purposes.
Insurance Backed.
To be PAS 2030 certified, installers must have an Insurance Backed Guarantee provider to ensure their customers are protected. They must also have adequate insurance coverage, including liability insurance, to protect homeowners.
What is an insurance backed guarantee? Installers will provide their own written workmanship guarantee (this is very important to get a copy of in case of any poor installations). This will outline a guarantee period, during which the installer will return and fix any faults resulting from faulty workmanship. The insurance backed guarantee only comes into effect if the original installation company ceases trading through lets say bankruptcy!. Ask for details of the company providing the guarantee, and then do your research.
All Insulation installed under PAS.
Each insulation installation will follow the same route as regards with ventilation on PAS. This should be explained by the retrofit coordinator and the installers. The basics are that background ventilation (usually trickle vents) will be provided unless an air permeability test is performed and validates the need to omit from the installation. Wet room ventilation is always required, but can vary with different insulation situations. (see below) If PIV (positive input ventilation) is being installed, then request details of why this choice is being taken, installers or retrofit coordinator will be able to guide you. (PIV will need maintenance, and it is placed in your loft space).
Some insulation situations like the property not being 100% insulated (bathrooms and kitchens being omitted due to fixture removal difficulty) then the extract ventilation may need to be a dMEV system to mitigate risks of condensation.
Pre-installation building inspection (PIBI)
The Retrofit Installer should undertake a pre-installation inspection using a competent person, this means a person or persons who have relevant industry qualifications. The inspection shall be undertaken at a level of detail sufficient to confirm that the specified energy efficient measure can be safely and effectively installed at the designated location. Particular attention shall be given to potential moisture build up as a result of the installation and taking into account the fire safety of the dwelling and the functionality and/or safety of installed services (gas, electricity, water, telecommunications, etc.)
Technical Monitoring.
Technical monitoring is a form of auditing that highlights a set of given questions on compliance. This is not performed by the installation company, but they may have their own regime of quality control. The funders (energy companies) will use these reports to highlight and hopefully rectify failing. Sadly, this shows that even with all the rules and hierarchy within the process of PAS, failing still arise. More on technical monitoring here.
When we insulate or upgrade a property, the original construction is just as important as the finished result.
Trying to achieve the unachievable often leads to failure and when it comes to improving our homes, that’s especially true if we ignore how they were originally built.
When we insulate or upgrade a property, the original construction is just as important as the finished result. Over the years, insulation has been added to homes that should never have been insulated, or where the wrong type of insulation was used entirely.
Old Homes Were Built to Breathe.
A typical Victorian house built around 1900 was designed very differently to the homes we build today.
Foundations were modest, often sitting on clay or mixed ground.
Damp courses were made from slate, bitumen, or engineering brick.
Mortars, plasters, and paints were lime-based, fully breathable.
Windows were single glazed timber-framed, and floors were usually suspended timber.
Each room had a fireplace, creating natural airflow through the chimneys.
And there were gaps, many gaps around windows, doors, floors etc.
Back then, heating revolved around open fireplaces burning solid fuels like coal and wood. Fireplaces not only warmed the room but also provided essential ventilation, drawing moisture and stale air out of the house.
Many homes even shared a single heat source, cooking in the kitchen typically provided much of the warmth and recreation. These homes were designed to breathe naturally, to dry out during warmer months and absorb some moisture during winter.
When we insulate or upgrade a property, the original construction is just as important as the finished result. Over the years, I’ve seen insulation added to homes that should never have been insulated, or where the wrong type of insulation was used entirely.
Today, the market is flooded with products, installers, and most of all funding. It’s easy to get swept up in the promise of “free” home upgrades, especially when companies that once specialised in one trade now offer everything from solar panels to external wall insulation. But not every measure suits every home.
Modern Living, Modern Heating.
Fast-forward over a century, and everything has changed. We’ve sealed, insulated, and upgraded our homes with new materials, plastic membranes, synthetic renders, dense boards, foams, and chemical coatings. We’ve replaced original windows with double/triple glazing, blocked up chimneys, and paved over soak aways (front gardens) for parking.
All of these change how our homes manage the movement of heat and moisture. We’ve also changed how we heat our homes:
Gas boilers became the norm through the mid to late 20th century, offering central heating at the touch of a thermostat.
Electric heating followed, from storage heaters to modern infrared panels.
Renewable systems are now taking the stage — air source and ground source heat pumps, solar PV, and hybrid systems.
Each of these heating methods interacts differently with the building fabric. For older homes, especially those built before 1930, installing insulation or modern heating without considering breathability can lead to damp, mould, and even structural damage.
Why Every Home Needs a Tailored Approach.
Before adding insulation or changing your heating system, it’s essential to understand how your home was meant to perform. A Victorian solid wall house behaves very differently from a modern cavity wall home, and what works brilliantly for one can cause real problems for the other.
The Key to a Warm, Healthy, Efficient Home.
When upgrading, the goal isn’t just efficiency, it’s balance. We need to make homes warmer and greener without disrupting how they naturally manage moisture and airflow.
By respecting your home’s original design, using the right materials, and combining insulation with proper ventilation, you can achieve comfort, efficiency, and longevity.
Meters need to be equipped with a unique reference to allow the collection of bills.
MPAN (Meter Point Administration Number) sometimes called an “Electricity Supply Number” is a unique 12-digit number that identifies the specific electricity supply point for a property in the UK. It’s used by electricity suppliers and network operators to ensure energy is correctly tracked and billed.
DNO (Distribution Network operator) Is a company that owns and manages the local infrastructurelike power lines, underground cables, and substations that deliver electricity to homes and businesses. Unlike your energy supplier, which sends your bill, the DNO is responsible for maintaining the physical network, fixing power outages, and handling new connections.
What an MPAN number does.
It tells energy companies exactly where electricity is delivered, similar to an address for your power connection. It will appear on your electricity bill and will usually be found in a box labelled “MPAN” or “Supply Number,” typically in the bottom section of your bill. This number is issued by your local Distribution Network Operator (DNO) Each DNO manages supply points in its region.
What is a DNO?
Across the UK, the electricity network is separated into individual regional areas, with each regional electricity grid controlled by the local Distribution Network Operator (DNO). Each regional grid is connected to the main National Grid. Within their respective areas, each DNO controls and operates substations that transmit electrical power to all users, including homes and businesses. When we generate power through solar, or we are taking from the network with the likes of heat pumps, the DNO needs to make sure we are not sucking too much power or pushing too much power back down the power lines.
Who are the UK’s DNOs?
Energy Networks Association, highlights how the UK’s electricity network is divided. The seven DNOs are as follows:
Over the years, many homes have been layered with materials like non-breathable paints, renders, pebble dashing.
Homes built in the UK before the 1980s often lack adequate insulation or have none at all. While building regulations at the time may have included some insulation standards, they were typically not enforced in practice. When planning insulation upgrades, it’s crucial to consider a range of “what if” scenarios and apply the latest insights (both scientific and lessons learned), as the field has advanced significantly. Any retrofit project should begin with a data-driven approach, starting with the property’s age and condition, which can offer valuable insights into how the process is likely to progress.
Over the years, many homes have been layered with materials like non-breathable paints, renders, pebble dashing, modern plaster finishes, and wallpapers. These additions can interfere with how the property breathes and manages moisture throughout the seasons. Addressing these complexities is essential when planning an insulation retrofit to ensure a balanced and effective outcome.
1300-1700 (Tudor era).
Timber-framed houses with thatched or tiled roofs were common in the early days (13/17th century), especially in rural areas. Vernacular techniques used local materials like timber, stone, or brick, varying by region.
Wealthier homes, particularly during the late 15th to early 17th centuries, featured brick, stone, steep gable roofs, and large chimneys. These types of properties need specialist insight when looking at a retrofit plan, as in most cases they will be of a significant interest and need an organic way to control moisture. The National Trust and English Heritage have some great information on the Tudor era.
1714-1837 (Georgian era).
Georgian architecture emphasised symmetry, proportion, and classical features, with terraced town houses becoming widespread in urban areas. Influenced by Palladian design (think the Royal Crescent in Bath), homes often had brick exteriors, sash windows, and decorative cornices. Rooms had high ceilings on 1st and 2nd floors and were also spacious. These properties like earlier techniques again need special attention and greater understanding when proposing a retrofit plan.
1837-1901 (Victorian era).
Rapid industrialization in the Victorian days led to mass construction of red-brick terraced housing for workers, particularly near factories. Middle-class homes were often larger, with ornate detailing like bay windows, plaster coving and decorative gables, reflecting Gothic Revival and Italianate influences. A lot of properties had cellars and coal chutes.
Advances in building materials like cast iron allowed for more elaborate designs.
The first cavity walls were constructed in Roman times, but it was in the Victorian era that cavity walls began to be used again, especially along the coast where properties would have high exposure to the elements.
1901-1914 (Edwardian era).
The Edwardian period followed, presenting larger, more spacious houses especially in suburbia reflecting the growing middle classes who wanted space and front gardens. These properties were more in line with the arts and craft movement and had a mix of cavity walls, possibly solid wall, timber framing and bay windows.
1914 and beyond (entering the modern era).
After the first world war, the government promoted the “homes fit for heroes” campaign and the Addison act was introduced. This act amended the law related to the housing of the working classes, town planning and the acquisition by local authorities of small dwellings. The Act imposed a duty on every local authority to survey housing needs and to make and carry out plans. It also guaranteed a state subsidy. The Addison Act was the start of a long tradition in the UK of housing provided by the state for the people. Old maps research can help with dating. This era was the birth of council housing and a move from mass private rental. Properties up to the second world war were a mix of bow windowed (some metal framed), bay windowed, art deco and some extravagant.
1945-1970 (Modern era).
After the mass house building of the past 20 years, the second world war then destroyed over 2 million homes. Most of the homes destroyed, and those left standing, still had outside lavatories and were heated by solid fuel. The councils began to build large estates and prefabricated houses to provide social housing to alleviate the housing crisis. This developed into high rise blocks that were built with steel, blocks and poured concrete.
1970-Present.
As ownership was encouraged by the government at the time, a lot of the cavity wall built council houses were now moving to private ownership. At the same time large out-of-town estates were being built by private developers and these too were mainly cavity wall (with no insulation). In recent years, there has been renewed focus on sustainable building and the development of high-density housing in urban areas due to rising property prices, population and environmental concerns. Mixed-use developments and flats have become more common in city centres.
Types of construction.
UK homes are typically classified into three different types of wall construction.
Solid Wall.
Cavity Wall.
Non-Standard Construction (System-Built).
Identifying the type of construction is essential for determining the best approach to installing insulation and controlling moisture.
Solid Wall.
Usually found in homes built before the 1920s. No cavity between the walls. Construction pattern (Flemish, English, common). Can vary in wall thickness from single brick at 150mm, to stone up to 500mm or more! Insulation Approach. Internal Wall Insulation (IWI). Insulation boards or stud walls filled with insulation material are installed on the inside of the external walls. More detail in the relevant insulation section. External Wall Insulation (EWI). Insulation material is fixed to the outside of the property and then covered with a protective render or cladding. More detail in the relevant insulation section.
Cavity Wall.
A cavity wall construction property has a cavity between the inner and outer walls. Common in homes built from the 1920s onwards. Consists of two parallel walls (inner and outer leaves) with a gap (cavity) in between. Originally, the cavity was designed to prevent moisture penetration, not for insulation. Cavity ties (what join the two leaves together) were either stone or later made of metal.
Insulation Approach. Cavity Wall Insulation (CWI). The cavity can be filled with insulation materials such as polystyrene beads, foam, or mineral wool. This is done by drilling small holes in the external wall and injecting the insulation. More detail in the relevant insulation section.
Non-Standard Construction Houses (System).
A non-standard construction house is any house that is not built of traditional materials such as brick or stone. These properties use alternative materials and construction methods.
Timber Frame.
Houses with a wooden structural framework, often with external cladding.
Advantages. Quick to construct, flexible design. Considerations. Potential issues with moisture and decay if not properly maintained.
Concrete Construction.
Houses with block concrete or poured, typically with external cladding.
Precast Concrete. Large concrete panels or blocks assembled on-site. In-Situ Concrete. Concrete is poured into frameworks directly on-site.
Advantages. Strong and durable. Considerations. Potential for thermal bridging, can be difficult to insulate.
Steel Frame.
Structural framework made of steel. Advantages. Strong and lightweight, allowing for large open spaces within the building. Considerations. Can be prone to corrosion if not properly protected.
Prefab (Prefabricated) Housing.
Sections of the house are manufactured off-site and then assembled on-site. Advantages. Rapid construction, consistent quality. Considerations. Joint integrity and insulation can be challenging.
Airey Houses.
Prefabricated concrete post-war homes were named after Sir Edwin Airey, who designed them.
Advantages. Quick to construct. Considerations. Many have since deteriorated and require significant maintenance or replacement.
Wimpey No-Fines.
Constructed with concrete made from large aggregates and no fine particles, designed by the construction company Wimpey. Advantages. Strong and provides good thermal mass. Considerations. Difficult to retrofit with insulation.
