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Home insulation cost: what it really costs in 2026
Loft, cavity and external wall.
£800 – £1,620 (loft & cavity)
Cavity wall insulation starts around £800 per house and loft insulation from £900. External wall insulation is the big one at £100–£160/m².
Price by spec
| Option | What it means | Typical price |
|---|---|---|
| Cavity wall | Injected, whole house | £800 – £1,200 |
| Loft top-up / full lay | To 270mm+ depth | £900 – £1,620 |
| External wall (EWI) | Solid-wall homes, rendered finish | £100 – £160 /m² |
What actually happens
- Survey — walls drilled-tested or loft measured
- Cavity: holes drilled in mortar joints and bead injected
- Loft: boards moved, rolls laid cross-ways to depth
- Pipes lagged and loft hatch insulated
- EWI: boards fixed to outside walls, mesh and render over
- Holes made good; certificates and guarantees issued
Popular choices
270mm+ loft depthBonded bead cavity fillEWI with brick-slip finishes
Regulations to know
- Cavity and EWI should come with a 25-year CIGA or equivalent insurance-backed guarantee
- EWI changes the house's appearance — planning permission needed in conservation areas and on some street-facing walls
- Building regulations apply to EWI thermal performance
Tips from the trade
- Loft insulation is the best £-for-£ energy upgrade in the house — do it before anything fancy
- Never let anyone fill a cavity with damp problems; fix the damp first
Plan this project properly
Get a region-adjusted estimate, track budget against real quotes, and find local tradespeople -- free to browse on Qome.
Start planning on QomePrices on this page are approximate, region-adjusted guide figures built from cross-checked UK cost data. They exist to inform you, not to bind anyone. Actual prices are whatever you and your tradesperson agree, and a difference between a Qome guide figure and a real quote is not a fault in either.