How much does cavity wall insulation cost?
Cavity wall insulation is injected into the wall cavity and priced by external wall area. Estimate yours below.
What cavity wall insulation involves
- 1Suitability survey
The installer checks the wall has a suitable, clean cavity — solid walls and some exposed locations aren't suitable.
- 2Injection
Insulation beads or foam are injected through small holes drilled into the mortar, which are then made good.
- 3Guarantee
Reputable installs come with a CIGA (or equivalent) guarantee — keep it with your property documents.
Where the walls have a suitable cavity, this is one of the cheapest EPC improvements available and a quick MEES win. On solid-wall stock you'll need internal or external insulation instead — a very different budget.
Cavity wall insulation costs (indicative)
| Property | Wall area | Indicative cost |
|---|---|---|
| Mid-terrace | ~50 m² | £600 – £1,250 |
| Semi-detached | ~90 m² | £1,100 – £2,250 |
| Detached | ~130 m² | £1,600 – £3,250 |
| Per m² | — | £12 – £25/m² |
For cavity walls only. Solid walls need internal or external wall insulation instead.
Frequently asked questions
How much does cavity wall insulation cost?+
Cavity wall insulation typically costs £12–£25 per m², so a semi-detached house (~90 m² of wall) is roughly £1,100–£2,250. It's a low-cost way to improve the EPC on suitable properties.
Is my house suitable for cavity wall insulation?+
Only homes with unfilled cavity walls in reasonable condition. Solid-wall properties (typically pre-1920s) need internal or external wall insulation instead. A survey confirms suitability.
Related tools & guides
Want to know how these figures are calculated? See our cost methodology.
Cost figures shown are indicative estimates, not quotations. You are responsible for verifying all costs (obtain contractor quotes) and any figures submitted to a lender. ScopeWise is a documentation tool, not financial, tax, structural or planning advice. HMO compliance prompts are guidance only — confirm requirements with your local council, as standards and licensing vary by authority.