Great British Insulation Scheme Failure: What Happens Next

The Great British Insulation Scheme failure has turned into one of the costliest lessons in recent UK energy policy. Government-backed programmes meant to cut fuel bills and keep vulnerable households warm have, in tens of thousands of cases, left homes damper and in need of expensive repairs. If your home had wall insulation fitted with public money between 2022 and early 2025, this story could be about your house.

Here is a plain-English guide to what went wrong, what the official watchdogs and MPs have found, how the repair effort is going, and what households can do right now.

Key facts at a glance

• Around 98% of external wall insulation jobs under ECO4 and the Great British Insulation Scheme (GBIS) need repair work, which could affect up to 23,000 homes.
• About 29% of internal wall insulation jobs are also affected, covering up to 13,000 homes.
• Repairs cost between £250 and £18,000 per home if tackled early, but the worst case found reached £250,000.
• Up to £165 million of ECO4 spending is suspected to have been claimed fraudulently.
• Only around 3,000 faulty homes had been found and fixed by autumn 2025, out of more than 30,000 estimated.

What the National Audit Office found

In October 2025 the National Audit Office (NAO) published a damning review of work carried out under the Energy Company Obligation (ECO4) and the Great British Insulation Scheme. Its report on faulty energy efficiency installations concluded that almost every external wall insulation job needed remedial work, and that nearly a third of internal wall jobs had serious problems too. A small share of the defects were judged to carry an immediate health and safety risk.

Damp, mould and rot were the most common consequences. Because the cost of a repair depends on how quickly it is carried out, delay is expensive. One home with faulty internal insulation needed £250,000 of work after damp, mould and dry rot took hold. Numbers like that show why the Great British Insulation Scheme failure is far more than a paperwork problem: it is a bill that grows with every winter a defective wall is left alone.

How did the Great British Insulation Scheme failure happen?

No single mistake explains it. The NAO pointed to a workforce that was too thin and too inexperienced, with jobs passed down to subcontractors who were not always competent or properly certified. There was also confusion over which technical standards applied to which properties, and some firms appear to have cut corners to hit volume targets. Only about 1% of external wall installations met the PAS 2035 retrofit standard.

The safety net failed to catch the problems in time. TrustMark, the quality scheme appointed by the government, did not warn the energy department about high levels of faulty external wall insulation until October 2024. By then ECO4 had been running for more than two years, since April 2022. Similar worries about internal wall insulation followed a month later. Many households had already lived through at least one winter with the consequences.

The design of the checks also mattered. The schemes tried to reduce risk by keeping the retrofit assessor and the retrofit coordinator as separate roles. In practice, the NAO found, both were often hired and paid by the installer, and sometimes worked for the same company. That undermined the independent scrutiny the system was supposed to provide.

Fraud made a bad situation worse

The audit also uncovered suspected fraud on a larger scale than in comparable retrofit schemes. Ofgem estimated that claims for work in as many as 16,500 homes may have been falsified, and that up to £165 million, around 3.9% of ECO4’s delivery cost, could have been claimed improperly. By contrast, annual fraud and error on the Renewable Heat Incentive and the Boiler Upgrade Scheme was put at roughly 1% and 2%.

Suspected fraud deepened the Great British Insulation Scheme failure because homes where work was done badly, or never done at all, are much harder to trace and put right. The NAO was also told of suspicions that installers claimed payment for households that were not eligible, and that some installations were used as part of wider criminal activity.

Find and Fix: how are repairs going?

After the report, ministers said no household should have to pay to fix botched work. The main tool is TrustMark’s “Find and Fix” programme, which arranges a free audit of affected homes and then requires the original installer to correct any faults. TrustMark and the certification bodies also suspended 38 installer businesses, which together accounted for 81% of the external wall insulation market. Some were later reinstated after promising to carry out repairs.

Progress has been slow. Nearly a year after the problems emerged, only about 3,000 defective homes had been found and fixed out of an estimated 30,000-plus, with around 20,000 external wall cases still outstanding in November 2025. In January 2026 the Public Accounts Committee published its own report on the scandal, calling for the programme to be scaled up and delivered in a much shorter timeframe. Some commentators went further and called for a Serious Fraud Office investigation.

Who pays for the Great British Insulation Scheme failure?

Legally, the installer that did the original job is responsible for putting it right. If that business has closed or refuses to act, a guarantee should step in, covering costs of up to £20,000. The catch is that MPs warned households do not yet have real assurance they will be protected, and that some company directors are closing firms and restarting under new names to avoid their duties. TrustMark itself reported that 27 of the 194 registered businesses with outstanding work were no longer registered.

There is one firm deadline to know about. TrustMark says it no longer accepts requests to extend the remediation period for ECO4 and GBIS measures inspected on or after 1 June 2026, and the standard repair window remains eight weeks.

Is your home affected? What to do next

You may be affected if you had insulation installed through ECO4 or the Great British Insulation Scheme between April 2022 and January 2025. If you think your home is caught up in the Great British Insulation Scheme failure, act sooner rather than later, because damage tends to worsen with time. Sensible steps include:

1. Check for warning signs. New damp patches, black mould, peeling paint, musty smells or rising heating bills can all point to a problem.
2. Find your paperwork. Look for the installer’s name, the guarantee and proof that the firm was registered with TrustMark.
3. Watch for contact from TrustMark. Letters offering a free audit are being sent to affected households.
4. Report problems in writing. Tell the installer first, and escalate to TrustMark or your local council if you get no response. Flag clearly if children, older people or anyone with a health condition lives in the home.
5. Do not pay up front. Faults should be fixed at no cost to you. Keep photos, emails and receipts.

Be careful about scams. TrustMark advises that anyone contacting you about an audit should be able to quote a Unique Measure Reference Number. If they cannot, share no personal details and do not let them into your home. Fraudsters trying to profit from the Great British Insulation Scheme failure rely on panic and confusion, so take your time and verify who you are speaking to.

Lessons for the Warm Homes Plan

ECO was due to close on 31 March 2026, and the Great British Insulation Scheme ran to the same month. The Department for Energy Security and Net Zero says it will apply the lessons to future programmes, including the forthcoming Warm Homes Plan. The NAO’s recommendations are straightforward: take full responsibility for schemes of this kind, set out clearly how faulty work will be repaired, rebuild consumer protection, and report every year on fraud and non-compliance.

The Great British Insulation Scheme failure also shows that volume and speed targets mean little without independent quality checks. Industry advisers stress that the problem is not insulation itself, which can cut bills and carbon when it is done properly. The trouble lies in poor installation, missing ventilation and non-compliance with building standards. A watchdog’s warning that the repair effort could shrink alongside the market is a reminder that skilled installers are needed to finish the clean-up even as the schemes close.

The bottom line

The Great British Insulation Scheme failure will take years to unwind. Tens of thousands of homes still need to be found, inspected and repaired, and the public has every right to ask how a programme meant to protect the most vulnerable households ended up putting some of them at risk.

For homeowners the message is simple: check your property, keep your paperwork, insist that any repair is free, and report problems early. For government, the Great British Insulation Scheme failure is a warning that green ambitions only deliver when quality, oversight and accountability are built in from day one.