If you had internal or external wall insulation fitted through ECO4 or the Great British Insulation Scheme, there is now an official route for checking affected work.

The important first step is not to assume that a crack, patch of mould or cold room proves your insulation is defective. Solid-wall problems can have several causes, and the government's remediation programme is specifically concerned with work installed through ECO4 and GBIS.

Here is how to work out whether your home falls within that process, what happens next and how to avoid paying for remediation that the official scheme says should be free.

The government guidance applies to internal wall insulation (IWI) or external wall insulation (EWI) fitted through ECO4 or the Great British Insulation Scheme. ECO4 installations are relevant from the scheme's start in April 2022.

These schemes operate in England, Scotland and Wales, not Northern Ireland.

If you are unsure how the work was funded, start with the paperwork you were given when it was installed. Look for references to ECO4, GBIS, the energy supplier involved, TrustMark, the installer, any guarantee provider and a Unique Measure Reference.

Ofgem has been sending letters to affected properties setting out the next steps.

Do not assume that because your home has solid-wall insulation it is automatically part of this programme. Privately funded work, older schemes and other insulation measures may follow different complaint or guarantee routes.

The clearest official instruction concerns external wall insulation.

GOV.UK says all properties that had EWI installed under ECO4 or GBIS will be offered a home check. Qualified professionals will inspect the insulation, and households may be contacted by Ofgem, TrustMark or the certification body that oversees the installer.

If faults are found, the original installer is expected to put them right. The government guidance is explicit that the household should not be asked to pay for this remediation.

That makes the official contact trail important.

Organisations involved in the process are expected to use the Unique Measure Reference shown in the Ofgem letter. If someone contacts you claiming to arrange a scheme inspection but cannot establish the official reference or you are uncertain who they are, do not hand over money or sensitive information. Verify the contact through Ofgem or TrustMark using details obtained independently from their official websites.

If you have already had a home check since January 2025, current government guidance says no further action is required through this particular process.

Internal wall insulation is not being treated in exactly the same way.

GOV.UK currently says that if you had IWI fitted, no action should be required. The government's statistical audit found substantially fewer major issues with internal wall insulation than with external wall insulation.

That does not mean every IWI installation is guaranteed to be fault-free.

If you have a specific concern — for example persistent damp, visible defects or a problem identified by a professional — the official guidance says you can contact Ofgem. A separate complaint can also be pursued through the relevant TrustMark process.

The distinction matters because headlines about the audit can easily make every insulated homeowner think they need an emergency survey. The current official route is universal checking for scheme-funded EWI; it is not a universal instruction to rip open or independently investigate every IWI installation.

The 2025 statistical audit was based on randomised samples of solid-wall insulation installed through ECO4 and GBIS in England, Scotland and Wales.

It found that 92% of the external wall insulation installations sampled had at least one major technical non-compliance that would affect system performance. The updated result for internal wall insulation was 27%.

Those are serious findings, but the scope needs to stay attached to the numbers. They describe the audited population of scheme-funded installations, not all external or internal wall insulation in Britain and certainly not all insulation as a building method.

A technical non-compliance also does not tell a homeowner, on its own, what repair their specific property needs. That is the purpose of the inspection and remediation process.

The detailed inspection belongs with the qualified people carrying out the scheme audit, not with the homeowner.

Your useful role is to make the visit easier to verify and document.

Before the appointment, gather:

- the Ofgem letter and Unique Measure Reference;
- original installation paperwork and dates;
- the installer's name;
- any TrustMark or certification information;
- the guarantee documents;
- photographs taken before, during or soon after the work, if you have them;
- a simple dated record of any problems you have noticed.

If there is damp or mould, record where it appears and when it is worst, but do not try to diagnose the cause yourself. Moisture can relate to rain penetration, plumbing leaks, ventilation, condensation, existing defects or the interaction between several parts of the building.

Similarly, do not start removing render, insulation boards or internal linings to “see what's behind them”. Destructive opening-up can create new weatherproofing, fire-safety or warranty problems and may interfere with the evidence needed for an official inspection.

The simple version of the policy is that the original installer is responsible for correcting defective work.

Real life is not always that tidy.

In a written parliamentary answer on 8 June 2026, the Department for Energy Security and Net Zero said that where an installer ceases trading or fails to rectify issues, solid-wall insulation measures have a guarantee covering up to £20,000. A later answer in June said a separate National Energy Foundation route exists for a small group of homes where there is non-compliant ECO4/GBIS solid-wall insulation and the original installer cannot rectify it while a valid guarantee is missing, fraudulent or cancelled.

That does not mean every household automatically receives £20,000. It describes the protection and fallback routes that may apply according to the circumstances of the installation.

If your installer has disappeared, do not assume you are stuck — but do not appoint a replacement at your own cost before checking the official route and your guarantee position.

Ofgem administers ECO but says it does not directly resolve ordinary complaints about ECO installations.

For installation complaints, its current guidance points homeowners towards TrustMark, the installer, the relevant scheme provider and, where applicable, an ombudsman. The special wall-insulation guidance should be followed first where ECO4/GBIS IWI or EWI is involved.

Keep a written chronology. Save emails and letters. Photograph visible changes. Ask for inspection findings and proposed remedial work in writing.

If a contractor proposes a repair, ask what defect has been identified, what standard the repair is intended to meet, what parts of the wall system will be disturbed and how weatherproofing, ventilation, fire performance and finishes will be reinstated.

You are not expected to become a retrofit specialist. You are entitled to know what is being corrected and why.

The official EWI remediation process is supposed to be free to the affected household.

That makes an unexpected demand for money a clear reason to stop and verify.

GOV.UK says Ofgem, TrustMark and relevant certification bodies may contact households and that the Unique Measure Reference should be used in those contacts. If you are unsure, contact Ofgem yourself rather than relying on a number or link supplied by the caller.

The current government contact details for wall-insulation queries include an Ofgem webform and the freephone number 0808 169 4447. Check the official GOV.UK page before using contact details because helplines and processes can change.

If your wall insulation was funded through ECO4 or GBIS:

For external wall insulation, look for the Ofgem letter and official home-check process. If you have not heard anything, or you are unsure, contact Ofgem through the official wall-insulation guidance.

For internal wall insulation, current guidance says no action should generally be required, but contact Ofgem if you have concerns.

If you have already had the scheme home check since January 2025, GOV.UK says no further action is required through that check programme.

If a separate problem exists, keep records and use the official complaint route rather than diagnosing or dismantling the insulation yourself.

And if someone asks you to pay for an ECO4/GBIS EWI remediation visit or repair, verify the approach before agreeing to anything.

The audit findings are serious. The most useful response for a homeowner is not panic; it is to make sure the right property enters the right official process and that any remedial work is properly documented.