How much does external wall insulation cost?
External wall insulation is priced by wall area. Enter your wall area below for a region-adjusted estimate.
What EWI involves
- 1Insulation boards
Insulation is fixed to the external walls, typically EPS or mineral wool.
- 2Render finish
A reinforced base coat and a through-coloured render finish over the insulation.
- 3Detailing
Window reveals, sills, verges and services all need careful detailing — a big part of the labour.
EWI is most attractive on solid-wall properties where the EPC is poor — improving the rating supports lettability under MEES and can lift the valuation. Check for available grants before pricing the full cost.
EWI costs (indicative)
| Property | Approx. wall area | Indicative cost |
|---|---|---|
| Mid-terrace | ~60 m² | £5,400 – £9,000 |
| Semi-detached | ~100 m² | £9,000 – £15,000 |
| Detached | ~140 m² | £12,600 – £21,000 |
| Per m² | — | £90 – £150/m² |
Includes insulation, render finish and scaffolding. Grants may be available for some properties.
Frequently asked questions
How much does external wall insulation cost?+
EWI typically costs £90–£150 per m², so insulating a semi (~100 m² of wall) is roughly £9,000–£15,000 including the render finish and scaffolding.
Does EWI improve the EPC?+
Yes — insulating solid or hard-to-treat walls significantly improves thermal performance and the EPC rating, which matters for lettings and resale.
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.