Cavity wall insulation cuts a typical home’s heat loss through walls by a third or more, and ECO4 funds it fully for eligible households. The gatekeeper is the pre-install suitability survey — the step that separates good CWI from the horror stories.
Follow the funded route before the December 2026 deadline — packages are surveyed, funded and installed at no or low cost.
Check CWI eligibility →You still have strong routes: Warm Homes: Local Grant (England), £7,500 BUS, 0% VAT to Mar 2027 and competitive private installation with one matched installer.
Check My Home →Good CWI requires: a genuine cavity of adequate width (typically 50mm+), sound external walls without failed pointing or persistent damp, and acceptable wind-driven-rain exposure for the property’s location. ECO4 surveys check construction (post-1930s builds usually cavity; verify via brick pattern and wall thickness), borescope the cavity, and assess exposure zones. Homes that fail get different measures — that’s the system working, not a rejection to argue with.
Same doors as all ECO4: the benefits route or council Flex, EPC D–G. CWI scores strongly in whole-house packages and pairs naturally with loft insulation in the classic two-measure project that lifts a D/E home substantially.
Historic problems came overwhelmingly from insulating unsuitable walls — exposed coastal properties, narrow or rubble-filled cavities, pre-existing damp. Modern scheme installation carries the survey discipline plus CIGA-backed guarantees (typically 25 years). Unsuitable wall? The right answers become solid-wall systems or targeted repairs first — and ECO4’s assessment routes you accordingly.
Survey, council declarations (Flex), and installation scheduling all consume weeks — against a hard scheme close of 31 December 2026 and no successor. Post-ECO4, funded CWI narrows to WH:LG eligibility in England; privately it runs around £2,700 for a typical semi (EST, May 2026) at 0% VAT.
Facts checked 21 August 2026. We link to official sources and show when facts were last verified. If a scheme changes, we update the page.
Free, independent, 60 seconds. We compare every option, check Government scheme eligibility and match you with one trusted local installer if you want one.
Check My Home →