Faulty energy efficiency installations

Status / emerging findings

• Between 22,000–23,000 homes (98% of external cladding installed to January 2025) have defects requiring remediation; a further 9,000–13,000 homes need major repairs for internal insulation failures.
• Defects emerged in October 2024, nearly two years after installations began in 2022. By November 2025 (one year later), only ~3,000 homes had been repaired—a rate the Chair called 'the worst failure' in 12 years on the Committee.
• TrustMark failed to recognise that the transition from single-measure to multi-measure ECO4 installations created higher risks; operational meetings between TrustMark and the Department were informal Teams calls without minutes, hampering escalation.
• UKAS's risk-based surveillance model placed new installers at the lowest risk level initially, when they should have been at the highest—a design flaw UKAS acknowledged only in October 2024.
• Data analytics systems that could have identified defects systematically were not implemented until late 2023–2024 due to lack of funding, leaving the Department unable to monitor quality at scale.

Why it matters

Over 30,000 UK homes are at risk of water ingress, mould, and condensation from faulty insulation installed via a government-backed fuel poverty scheme; understanding what went wrong is essential for preventing similar failures in future retrofit programmes.

Tone arc

Started procedural and accountability-focused; became increasingly adversarial in the November 2025 evidence session as witnesses conceded systemic failures and the Committee pressed on why early warning signs were ignored for two years.

Key witnesses

Jeremy Pocklington CB (Department for Energy Security & Net Zero), Clive Maxwell CB CBE (Department for Energy Security & Net Zero), Simon Ayers (TrustMark), Jonathan Brearley (Ofgem), Deborah Chittenden (UKAS/accreditation body), Matt Gantley (Installation Assurance Authority Federation)