Walls
Walls lose more heat than any other part of an uninsulated home. Whether they can be filled depends on whether they are cavity or solid.
The short answer
- About £2,200 for a typical home, and often free through a grant
- A median 12.0% less gas afterwards, about £105 a year for a 3 bed semi
- About 21 years to pay back at full price, so it pays best with a grant
Calculators
Guides
Is Cavity Wall Insulation Worth It?Cavity wall insulation costs about £2,200. Homes used 12% less gas after it, about £105 a year for a 3 bed semi. Who it suits, damp risks and free grants.
Solid Wall Insulation Cost UK 2026Solid wall insulation costs about £12,000 inside or £15,000 outside for a 3 bed semi. Homes used 17.3% less gas after it: about £151 a year.
Underfloor Insulation Cost UK 2026Insulating a suspended timber floor costs £1,400 to £2,500 and saves about £55 a year in a semi, says the Energy Saving Trust. Floor types, DIY, damp.
Insulation Cost by House TypeCavity wall insulation from £950 for a flat to £3,900 for a detached house, loft and solid walls too, with measured savings and payback.Insulation Cost for a Semi-Detached HouseLoft £600 to £750, cavity walls £2,200, solid walls £12,000 to £15,000: insulation costs and measured savings for a semi-detached house.Insulation Cost for a Detached HouseLoft £800 to £1,100, cavity walls £3,900, solid walls £12,000 to £15,000: insulation costs and measured savings for a detached house.
Insulation Cost for a Terraced HouseLoft £500 to £650, cavity walls £1,100, solid walls £12,000 to £15,000: insulation costs and measured savings for a terraced house.Insulation Cost for a BungalowLoft £800 to £1,200, cavity walls £1,700, solid walls £12,000 to £15,000: insulation costs and measured savings for a bungalow.
Insulation Cost for a FlatLoft £500 to £650, cavity walls £950, solid walls £12,000 to £15,000: insulation costs and measured savings for a flat.