Cavity wall insulation cost (2026)

Cavity wall insulation cost (2026). The published installed range in 2026 is £18 to £28 per m² installed (CIGA publisher, GBIS-funded job sheets), or £1,200 to £2,600 for a typical 3-bed cavity semi gross, and often £0 net after GBIS or ECO4. Both ends of that range are stated rather than collapsed to a midpoint, because the spread reflects real differences in scope, access and grant eligibility rather than installer mark-up.

• Fill type: mineral fibre vs EPS bead vs polyurethane foam. Bead is the modal 2026 fill.
• Exposure rating dictates whether the cavity can be filled at all.
• Whether a previous fill has failed and needs extraction (a £1,500 to £3,000 add-on).
• GBIS or ECO4 funding strips most or all of the gross cost for eligible households.

PAS 2035 Path A unless paired with another measure that triggers Path B or C.