On 17 July the Government updated the House on widespread, systemic issues in the delivery of solid wall insulation under the energy company obligation 4 scheme and the Great British insulation scheme1. The statement, published in Hansard on 13 October 2025, set out the results of an independent audit programme and the actions being taken in response1.
Around 65,000 households have received solid wall insulation installed under those schemes, which place obligations on large and medium-sized energy suppliers to install energy efficiency improvements, typically delivered through contractors. ECO4 commenced in 2022 and GBIS in 20231. The audit found that 92% of external wall insulation installations and 27% of internal wall insulation installations audited under these schemes had at least one major technical non-compliance, defined as an issue that compromises the effectiveness of the insulation rather than posing a direct risk to safety. A further 6% of EWI and 3% of IWI installations audited were categorised as posing potential risks to health or safety; where such risks are identified, installers are required to make them safe within 24 hours1.
| Measure audited | Major technical non-compliance | Potential health or safety risk |
|---|---|---|
| External wall insulation (EWI) | 92% | 6% |
| Internal wall insulation (IWI) | 27% | 3% |
The statement said the issues resulted from "unacceptably poor standards of work from a number of contractors, enabled by a flawed oversight and protection system established by the previous Government", and that in the most severe cases this had led to damage to homes, including serious problems with mould and damp1. TrustMark, the independent body overseeing retrofit work quality, identified significant levels of poor-quality solid wall insulation in routine audits in October 2024 and began suspending installers, after which the Department commissioned a fuller audit1.
"Results show that 92% of external wall insulation installations and 27% of internal wall insulation installations of those audited under these schemes were found to have at least one major technical non-compliance."
The Government said 38 installers have been suspended, with a process for reinstatement following remediation of all issues in identified properties, alongside enhanced checks by energy suppliers, greater departmental oversight of TrustMark, restrictions preventing installers from operating through multiple certification bodies, and updated standards requiring site visits from retrofit co-ordinators1. Audits of the social housing decarbonisation fund, home upgrade grant and local authority delivery schemes showed no widespread problem, which the statement attributed in part to greater oversight and scrutiny1.
Why it matters for households
Solid wall insulation is one of the more consequential insulation measures for a home's heat loss, and the audit results mean a large share of externally insulated homes under these schemes may not be performing as intended. A major non-compliance compromises effectiveness rather than safety, so a household may see less benefit to bills and warmth than expected without any obvious sign of a fault. The smaller proportion flagged for potential health or safety risk, including the mould and damp problems described, bears directly on how safe and habitable a home is1. Installers are responsible for putting right issues found with their work, and the statement said no household should be asked to pay any money to put things right1. Where an original installer is no longer trading, works under ECO4 and GBIS must be covered by guarantees, and householders can contact their guarantee provider1. The statement also said the failures point to oversight gaps rather than to the principle of the schemes, and that retaining public confidence in home upgrades is treated as necessary to cutting bills and delivering warmer homes1.
What happens next
The Government is offering comprehensive on-site audits to every household with external wall insulation installed under the two schemes, at no cost to the consumer, with affected households initially contacted by Ofgem1. Ofgem's contact centre is available on 0808 169 4447, Monday to Friday excluding bank holidays, from 9.30 am to 4.30 pm, by email at ECOhelD@ofgem.gov.uk, and through a webform on gov.uk pages1. The Department will consult on proposals for a single system of oversight for retrofit work early next year, with further detail to be provided in the warm homes plan1.
Sources1 cited
- Retrofit Measures: ECO4 and GBIS - Hansard - UK Parliament, hansard.parliament.uk