Guide, Updated October 2026

Fitted With External Wall Insulation Under ECO4 or GBIS? What to Do Next

If external wall insulation was fitted to your home through a government-backed scheme, you may have heard that many of those installations have been found to have faults. Here is what has been reported, what the official check involves, and what you can sensibly do next.

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What has been reported

In October 2025 the National Audit Office (NAO) published its findings on installations under two government schemes: the Energy Company Obligation (ECO4) and the Great British Insulation Scheme (GBIS). In January 2026 the Public Accounts Committee followed up with its report, Faulty energy efficiency installations.

The audit was based on a sample of homes, and the figures relate to scheme-funded installations only. They do not describe every EWI job in the UK, and they say nothing about work paid for privately outside these schemes. We are an EWI specialist, not a government body, so for anything official always use the contact details on GOV.UK.

What the Committee says

32,000 to 35,000 homesBetween 32,000 and 35,000 homes with external or internal wall insulation are likely to be affected.

98% of EWI homes98% of homes with external wall insulation have major issues, which the Committee puts at between 22,000 and 23,000 homes.

Performance and safetyWithin that group, 92% have defects that will negatively affect the insulation's performance, and 6% have immediate health and safety risks, such as inadequate ventilation.

Probably higherThe estimates cover installations up to mid-January 2025. The Committee said the true total will be higher, because the Department for Energy Security and Net Zero has no estimate for later installations.

The official check

What the government is asking homeowners to do

GOV.UK's insulation check page sets out the process for homes with external wall insulation fitted under these schemes.

A home check

GOV.UK says all properties which had external wall insulation installed under these schemes will be offered a home check, and that the work will be quality checked by qualified professionals. If you have had a home check since January 2025, it says no further action is required.

Who may contact you

Ofgem, TrustMark or a certification body may contact you. They will refer to a Unique Measure Reference, which appears in your letter.

Is it genuine?

If you are unsure whether a caller or message is genuine, do not give details. Use the number on GOV.UK instead: 0808 169 4447, Monday to Friday, 9:30am to 4:30pm, except bank holidays, at the time of writing.

Who pays if faults are found?

GOV.UK states that if faults are found your installer will be asked to fix them, and that you should not be asked to pay any money for this work. The National Audit Office says the original installer is liable for the whole cost of repairing faulty installations.

The Committee also said ministers have stated that no household should have to pay, but it was not convinced every household would be protected. Figures on how many homes have been repaired differ by date and by what is counted, so check GOV.UK for the latest position.

If an installer stops trading or fails to fix the problems, a guarantee should cover remediation costs up to £20,000
Guarantee claims can involve TrustMark's dispute process first
The guarantees do not pay compensation for ill health or lost earnings caused by mould
TrustMark advises that correcting faulty installations should normally cost between £250 and £18,000 per home; the worst case the Committee is aware of cost over £250,000 to fix the defects and resulting damage

Signs worth looking out for

You do not need to be an expert to spot early warning signs. If you notice any of the following, photograph them and report them, whether or not your work was scheme-funded.

Cracks do not always mean a system has failed, but they are worth checking early, before water has a chance to cause damage. Our guide to EWI problems and fixes explains what each one can mean.

Damp patches or mouldOn internal walls, particularly on walls that have been insulated.

Cracks in the renderEspecially around windows, sills and corners.

Hollow-sounding renderRender that sounds hollow when tapped can mean it has come away from the system behind it.

Staining or gapsStaining beneath window sills, or gaps where the system meets pipes and vents.

Do I need an independent opinion?

The official check is the first step if your work was scheme-funded. Some homeowners also want a second opinion from someone with no connection to the original installer, for example if they are waiting for a check, if they are unsure what a report means, or if the work was done privately.

That is what our consultation service is for. Where a visual or technical look at the walls is useful, our inspection service can help. If a system does need repair, our remediation work covers fixing failed systems properly rather than patching over the symptoms.

A note on grantsWe advise on grant and scheme questions, but we do not deliver grant-funded work.

If you are thinking about EWI now

None of this means external wall insulation is a bad idea. The NAO's headline was about weak controls and oversight of scheme installations. A well-specified, properly detailed and independently checked system is a different proposition.

Our external wall insulation guide explains how a system is made up, and our costs and grants guide covers current funding routes. If you are planning a new installation, it is worth reading how we approach installation, including independent advice and a survey before any specification.

FAQ

ECO4 and GBIS insulation check questions

I had EWI fitted under ECO4 or GBIS. Do I have to do anything?+

GOV.UK says all properties with EWI installed under these schemes will be offered a home check, and that you may be contacted by Ofgem, TrustMark or a certification body. If you have not heard anything and are worried, use the contact details on GOV.UK.

Will I have to pay for repairs?+

GOV.UK states you should not be asked to pay any money for this work. The Public Accounts Committee says a guarantee should cover remediation costs up to £20,000 if an installer stops trading or fails to fix the problems, but it was not convinced every household would be fully protected.

How do I know if a call or letter about my insulation is genuine?+

Official contacts quote your Unique Measure Reference. If you are unsure, do not share personal details, and ring the freephone number on GOV.UK instead.

Is cracked render always a sign of faulty EWI?+

Not always. Hairline cracking can be cosmetic, but cracks around windows, sills and junctions can let water in. Have it looked at sooner rather than later.

Does this affect EWI that was paid for privately?+

The reported figures relate to ECO4 and GBIS installations. Privately funded work is not covered by those figures, but the same detailing principles apply, so a check is still sensible if you notice damp or cracking.

Can Andrra carry out my home check or fix grant-funded faults?+

The official checks are arranged through the scheme bodies, so start with GOV.UK. We can give independent advice, inspect the walls and, where appropriate, repair failed systems. We advise on grant questions but we do not deliver grant-funded work.