Insulation cost by house type
The short answer
- £950 to £3,900 for cavity wall insulation, from a flat to a detached house
- £500 to £1,200 for loft insulation, and about £12,000 to £15,000 for solid walls in any home
- About 12 years to pay back cavity walls in a mid-terrace, against 28 in a 4 bed detached house
Updated 25 September 2026. Every figure on this page comes from our published model; see where our data comes from.
What loft, cavity wall, solid wall and floor insulation cost for each type of home, at Energy Saving Trust prices, and what homes that had it fitted saved on gas. Cavity wall insulation runs from £950 for a flat to £3,900 for a detached house; our cavity wall insulation cost guide covers the measured savings, damp risk and free grants.
Insulation cost by house type
Cavity walls pay back fastest in smaller homes. A mid-terrace pays about £1,100 and saves about £94 a year; a detached house pays £3,900 and saves about £139.
| Home | Loft | Cavity walls | Cavity saving a year | Cavity payback |
|---|---|---|---|---|
| Detached house | £800 to £1,100 | £3,900 | £139 | 28 years |
| Semi-detached house | £600 to £750 | £2,200 | £105 | 21 years |
| Terraced house | £500 to £650 | £1,100 | £94 | 12 years |
| Bungalow | £800 to £1,200 | £1,700 | £110 | 15 years |
| Flat | £500 to £650 | £950 | £68 | 14 years |
The data behind this table
Costs: Energy Saving Trust, typical professional installation before any grant, updated 8 May 2026; the loft range runs from a top-up from 120mm to a bare loft, and a flat's loft figure is borrowed from the mid-terrace. Savings: the median 12.0% fall in gas use measured after cavity wall insulation (DESNZ NEED Impact of Measures 2026), for a 4 bed detached house, 3 bed semi, 3 bed mid-terrace, 3 bed bungalow and 2 bed flat on gas at the October 2026 cap. Solid wall insulation costs about £12,000 inside or £15,000 outside for any home, and a suspended timber floor £1,400 to £2,500.
Your type of home
Pick your home for every measure, with savings by size and the grants.
- Insulation cost for a detached house
- Insulation cost for a semi-detached house
- Insulation cost for a terraced house
- Insulation cost for a bungalow
- Insulation cost for a flat
Or work it out for your own home, with the insulation you have now, in the insulation calculator.
Frequently asked questions
How much does insulation cost for my type of house?
Cavity wall insulation costs about £950 for a flat, £1,100 for a mid-terrace, £1,700 for a detached bungalow, £2,200 for a semi and £3,900 for a detached house, at Energy Saving Trust prices. Loft insulation costs £500 to £1,200 and solid walls about £12,000 inside or £15,000 outside.
Which insulation pays back fastest?
Cavity wall insulation in a smaller home: about 12 years in a 3 bed mid-terrace and 14 in a 2 bed flat, on the measured gas savings. Solid wall insulation takes over 50 years at full price, so it pays best with a grant.
Data sources
- Energy Saving Trust, cavity wall and loft insulation advice, updated 8 May 2026.
- DESNZ, NEED Impact of Measures 2026.