TrustMark and the certification bodies suspended 38 installer businesses from government retrofit schemes, representing 81% of the external wall insulation market, according to a Committee of Public Accounts report published on 23 January 20261. The suspensions followed TrustMark's notification to the Department for Energy Security and Net Zero in October 2024 of high levels of external wall insulation installations that were not compliant with quality standards, with similar issues flagged for internal wall insulation the following month1.
By the end of January 2025, 38 installers had been suspended1. As of November 2025, 22 installers had been fully reinstated after meeting requirements on TrustMark's "robust six-point plan", including full remediation of the problems identified1.
The committee found that 98% of external wall insulation and 29% of internal wall insulation installed under ECO4 and the Great British Insulation Scheme up to mid-January 2025 had major issues needing remediation, affecting between 32,000 and 35,000 homes1. Of these, 6% and 2% respectively had defects posing immediate health and safety risks, such as inadequate ventilation1. Nearly one year after the problems emerged, around 3,000 homes had been found and fixed1.
The Department accepted that the system was "too layered, fragmented and complicated and has not provided the protection that consumers deserve"1. The committee said the Department recorded a risk in November 2022 that TrustMark might not carry out compliance checks on time or to the correct standard, and identified a further risk in June 2023 that failures in wider compliance and assurance processes could limit installation quality1. Neither TrustMark nor the Department have been able to provide minutes of meetings which took place between 2022 and 20241.
"TrustMark and the certification bodies suspended 38 installer businesses, representing 81% of the external wall insulation market"
On remediation costs, the committee said it should normally cost between £250 and £18,000 per home to correct an installation, but in the worst case it was aware of a cost of over £250,000 to fix defects and resultant damage1. The original installer is liable for fixing the installation, and costs up to £20,000 should be covered by a guarantee when the installer has ceased to trade or fails to remediate1.
| Measure | Suspended | Reinstated by November 2025 |
|---|---|---|
| Installer businesses | 38 | 22 |
Why it matters for households
The suspensions removed a large share of the businesses able to carry out external wall insulation under these schemes, at a point when the committee says around 20,000 homes with faulty external wall insulation still needed to be found and fixed as of November 20251. For a household with an existing installation, the practical question is who is liable for repairs and whether a guarantee covers the cost. The committee said the original installer is liable, with guarantees covering costs up to £20,000 where the installer has ceased trading or failed to remediate, and that some remediation costs will exceed that cap1. It also said some company directors are closing and restarting their businesses to avoid remediation responsibilities1.
For households considering new work, the committee's finding that the Department accepted its consumer protection and quality assurance system was "too layered, fragmented and complicated" bears on how certification and redress operate in practice1. The committee recommended that no more external or internal wall insulation be installed through the Department's retrofit schemes unless every new project can be supervised and checked by someone independent, competent and accountable1. The Department has said no household should have to pay to fix the issues1.
What happens next
The government has announced it will end ECO, with no levies on consumer bills from April 2026, while continuing to invest in tackling fuel poverty through its Warm Homes Plan1. The Department is yet to confirm whether it will extend the period for suppliers to meet their existing ECO4 obligations beyond March 20261. The committee asked the Department to write within two weeks of the report with a plan for ensuring no household pays for repairs, and to confirm it is working with Companies House and The Insolvency Service to reduce the risk of directors closing and restarting businesses1. TrustMark expects to have audited all relevant homes for external wall insulation within 15 months of November 2025, providing access is granted1.
Sources1 cited
- Faulty energy efficiency installations, publications.parliament.uk