Typical UK cost: £95–£135 per m² installed — around £18,000 for a typical three-bed semi (EST, May 2026). Calculate your property below, then check whether funding removes the bill entirely.
EWI is the biggest-ticket insulation measure — and the biggest single heat-loss fix for solid-wall homes. Whole-property ranges: 2-bed terrace £9,000–£14,000; 3-bed semi £15,000–£21,000; 4-bed detached £21,000–£30,000. Terraces cost least (fewer exposed walls), detached most. All figures include scaffolding, standard render and 0% VAT (to 31 March 2027).
Scaffolding (£800–£2,500 by height/access), finish (standard render cheapest; coloured/textured +10–15%; brick-slip +25%+), insulation material (EPS most economical; mineral wool for fire/breathability; PIR where depth is constrained), labour (region and wall condition — repairs before boarding add cost), and detailing around windows, soffits and services.
Solid-wall insulation is a priority measure in both live schemes: ECO4 (benefits/Flex households, EPC D–G, to Dec 2026) and the Warm Homes: Local Grant (up to £15,000 fabric funding, to Mar 2028). It could be fully funded for some eligible households — eligibility does not guarantee installation or zero customer contribution.
Internal (IWI) runs ~£12,000 for the same semi — cheaper, but you lose room space, redecorate every treated room, and bridge less thermal detail. EWI protects the fabric, adds nothing inside, and refreshes the façade. Rule of thumb: EWI where planning allows; IWI for conservation areas and flats.
Indicative estimate — never a quotation. Survey-confirmed prices vary with wall condition, access and finish.
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.
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