Research and analysis

Solid wall insulation installed under ECO4 and GBIS: Statistical audit results

Results of an audit of solid wall insulation installed through government schemes.

• From: Department for Energy Security and Net Zero and Ofgem
• Published: 13 October 2025
• Last updated: 3 November 2025 — See all updates

Applies to England, Scotland and Wales

Documents

Solid wall insulation installed under ECO4 and GBIS: Statistical audit results

HTML

Details

In 2024 TrustMark reported quality issues with some solid wall insulation installed through the following government schemes:

• Energy Company Obligation (ECO4)
• Great British Insulation Scheme (GBIS)

This report summarises the results of a randomised sample of audits, commissioned by Ofgem, to understand the extent of non-compliance in solid wall insulation measures installed under these schemes.

Published 13 October 2025

Last updated 3 November 2025 + show all updates

1. 3 November 2025

   The statistical audit results were updated to correct the percentage of Internal Wall Insulation (IWI) installations.

2. 13 October 2025

   First published.