Great British Insulation Scheme (GBIS) Problems: What Homeowners Need to Know
The Great British Insulation Scheme ran from April 2023 until it closed on 31 March 2026. Official audits later found serious problems with wall insulation fitted under GBIS and ECO4. The scheme has ended, but faulty work can still be checked and put right. This guide explains what went wrong and where to go.
Insulation Crisis Help is an advice and introduction service run by Better Home Hub Ltd. We are not a government body, Ofgem, TrustMark or part of any government scheme.
What Was the Great British Insulation Scheme (GBIS)?
GBIS, formerly known as ECO+, was an obligation on energy suppliers to fund insulation, administered by Ofgem. It mostly delivered single insulation measures such as cavity wall and loft insulation, but it also funded external and internal wall insulation. It had broader eligibility than ECO4. It closed on 31 March 2026 with no extension, and the gov.uk eligibility checker has closed.
GBIS Key Facts
GBIS vs ECO4: What's the Difference?
Many homeowners confuse GBIS with ECO4 (Energy Company Obligation 4). Both were funded by energy suppliers and overlapped in time, but they had different eligibility and focus. For faulty wall insulation, the repair routes are the same under both.
| Feature | GBIS | ECO4 |
|---|---|---|
| Primary Focus | Mostly single insulation measures | Multi-measure retrofits, including heating |
| Eligibility | Low-income households, or homes rated EPC D to G in Council Tax bands A to D (England) or A to E (Scotland and Wales) | Mainly households on certain benefits, or referred by their council |
| Status | Closed 31 March 2026 | Ends 31 December 2026, winding down |
| External wall insulation | Funded; free TrustMark Find & Fix audit | Funded; free TrustMark Find & Fix audit |
| Internal wall insulation concerns | Ofgem ECO contact centre | Ofgem ECO contact centre |
What Went Wrong
1. Wall Insulation Audit Results
Ofgem commissioned audits of a representative sample of 758 homes with external or internal wall insulation fitted under GBIS and ECO4 before mid-January 2025. The results below cover both schemes together.
Source: National Audit Office, HC 1334 (14 October 2025).
2. Insulation Not Suited to the Building
Insulation that is not suited to a home, or is badly detailed, can trap moisture or let rain in. Under the retrofit standards that applied to the schemes (PAS 2035 and PAS 2030), the whole home should be assessed before work starts.
Homes Needing Extra Care
- Older homes with solid walls
- Homes with existing damp problems
- Homes with poor ventilation
- Walls exposed to driving rain
- Listed or conservation area buildings
What Should Happen
- A retrofit assessment of the whole home before work
- Moisture and ventilation considered in the design
- A retrofit coordinator overseeing the project
- A site visit by the retrofit coordinator on wall insulation jobs
- Handover paperwork and a 25-year guarantee certificate
3. Installer Quality and Oversight
By the end of January 2025, 38 installers had been suspended from government schemes — the department said this was 81% of the external wall insulation market — and 22 were later reinstated after fixing identified defects. When the Public Accounts Committee reported in January 2026, there was still no requirement for the retrofit coordinator to be independent of the installer.
4. Gaps in Consumer Protection
The Public Accounts Committee heard from households affected by poor-quality work. The problems it described include:
What Households Reported
Left Without Heating
Some people who used Ofgem's ECO helpline reported being left without central heating over winter, or having to find somewhere else to stay.
Damage Beyond the Walls
Households reported water damage to ceilings and paying hundreds of pounds to replace carpets and repair decoration.
Losses the Guarantees Do Not Cover
TrustMark confirmed the guarantees do not cover compensation for ill health or loss of earnings.
Slow Routes to a Fix
If the installer still trades but will not fix the work, you must go through TrustMark's dispute process to the ombudsman before a guarantee steps in. The Committee was concerned this takes too long.
How Problems Tend to Show
Cavity Wall Insulation and Penetrating Damp
Cavity wall insulation can carry rain across to the inner wall where walls face driving rain, the cavity is unsuitable, or the outer brickwork or pointing is in poor repair. Cavity wall insulation usually has a separate 25-year guarantee, often from CIGA or the Installation Assurance Authority — see our CIGA guarantee guide.
Signs worth reporting:
- Damp patches on internal walls, especially after rain
- Mould in corners or around windows
- Cracked, bulging or stained render on external wall insulation
- More condensation than before the work
- A musty smell or peeling wallpaper
Loft Insulation and Condensation
Loft insulation that blocks ventilation at the eaves can lead to condensation in the roof space. Check that vents have not been covered.
What to Do If Your GBIS Installation Has Failed
Step 1: Document Everything
- Take dated photos and videos of damp, mould or damage.
- Find all paperwork: contracts, guarantee certificates, Ofgem letters and assessment reports.
- Keep a diary of when problems appeared and how they have changed.
- Keep receipts for anything you have had to pay for because of the problem.
Step 2: Use the Free Route for Your Insulation Type
- External wall insulation: book TrustMark's free Find & Fix audit on 0333 555 1234 (option 1). See our guide to the free audit.
- Internal wall insulation: contact Ofgem's ECO contact centre on 0808 169 4447 or ECOhelp@ofgem.gov.uk.
- Cavity wall, loft and other measures: complain in writing to the installer, then to its TrustMark Scheme Provider, then to the Dispute Resolution Ombudsman. For cavity wall insulation, you can also contact the guarantee provider.
You should not be asked to pay for repairs to faulty scheme work. Anyone contacting you about the audit should be able to quote the Unique Measure Reference Number from your Ofgem letter.
Step 3: Get Independent Advice if You Need It
You do not need to pay for a survey to use the free routes. If no free route covers you, or you want independent evidence, a surveyor who is independent of the installer can help. Get a fixed quote first.
Step 4: If the Free Routes Do Not Resolve It
The Citizens Advice consumer helpline (0808 223 1133) can advise and can refer complaints to Trading Standards. For anything beyond that, get independent legal advice.
Your Legal Rights
Consumer Rights Act 2015
For contracts from 1 October 2015, a trader must perform a service with reasonable care and skill. How this applies to scheme-funded work depends on your contract, so take advice.
Time Limits
TrustMark's complaints process cannot help with work more than 6 years old (5 in Scotland). Court time limits also apply: in England and Wales, generally 6 years for a contract claim; in Scotland, generally 5 years.
Small Claims
The small claims track covers claims up to £10,000 in England and Wales, and £5,000 in Scotland (simple procedure) and Northern Ireland.
Who Pays for Repairs
There is no government compensation scheme. The official position is that faulty scheme work should be repaired at no cost to the household. Responsibility runs in this order:
- The original installer, which is liable for fixing the work
- The 25-year guarantee, if the installer has stopped trading or will not fix it: up to £20,000, or £25,000 for Installation Assurance Authority guarantees since 17 June 2026
- The National Energy Foundation, for some homes where the installer has gone and the guarantee was cancelled, fraudulent or missing
The guarantees do not cover ill health, damaged belongings or loss of earnings. For losses like these, get independent advice, for example from Citizens Advice.
If You Are Offered Insulation Now
Checks Before Agreeing to Work
- 1.Ask for a whole-home retrofit assessment before work starts, covering wall construction, moisture and ventilation.
- 2.Ask who will provide the guarantee and check the provider is on TrustMark's list of approved guarantee providers.
- 3.Check the installer yourself on the TrustMark register and Companies House, including how long it has traded.
- 4.Get the paperwork including the contract and guarantee details, and keep copies.
- 5.Ask about local jobs the installer has done, and speak to those households if you can.
- 6.Do not be rushed take time to read everything before you agree to any work.
Red Flags to Watch For
What Has Happened Since
- GBIS closed on 31 March 2026. ECO4 was extended to 31 December 2026 and no successor supplier obligation is planned.
- The Warm Homes Plan, published on 21 January 2026, sets out future government support for home upgrades.
- The Public Accounts Committee report (23 January 2026) called for no more external or internal wall insulation under government schemes unless independently supervised and checked.
- The government's response (Treasury Minutes, April 2026) disagreed with halting that work, but confirmed referrals to the Serious Fraud Office. It said TrustMark's Find & Fix programme reached full operation in late January 2026 and is intended to finish by May 2027.
- A consultation on reforming consumer protection for home upgrade schemes closed on 10 September 2026.
If No Free Route Covers You
Use the free routes above first. If none applies, tell us about your home and we can introduce you to a specialist through Better Home Hub. Sending an enquiry is free; any survey or work is agreed and paid for between you and the specialist, who may pay Better Home Hub a fee.
Tell us about your homeFrequently Asked Questions
Is GBIS the same as the Green Homes Grant?
No. The Green Homes Grant voucher scheme closed to applications on 31 March 2021. GBIS was a separate energy supplier obligation that ran from April 2023 until 31 March 2026.
Can I still apply for GBIS?
No. GBIS closed on 31 March 2026 with no extension. ECO4 ends on 31 December 2026 and is winding down. The Warm Homes Plan sets out future government support.
Who pays for GBIS remediation if it fails?
The original installer is liable. If it has stopped trading or will not fix the work, the 25-year guarantee should cover repairs up to its limit. There is no government compensation scheme, but households should not be asked to pay for repairs to faulty scheme work.
How long do GBIS guarantees last?
The government says all external and internal wall insulation under ECO4 and GBIS should have a 25-year guarantee. For cavity wall or loft insulation, check your guarantee certificate.
Sources
- Ofgem — Great British Insulation Scheme
- National Audit Office — Energy efficiency installations under the Energy Company Obligation (HC 1334, 14 October 2025)
- Public Accounts Committee — Faulty energy efficiency installations (HC 1229, 23 January 2026)
- HM Treasury — Treasury Minutes (April 2026)
- TrustMark — Free Find & Fix audit offer
- TrustMark — complaints process
- DESNZ — Greater protections to restore families' trust in home upgrades (17 June 2026)
- gov.uk — Warm Homes Plan
- HomeOwners Alliance — survey costs
Last reviewed September 2026.