Calculate your insulation cost
Loft and cavity-wall insulation by property type
Cavity wall £950
Cavity wall £1,800
Cavity wall £2,700
Cavity wall £4,600
Cavity wall £2,400
Cavity-wall cost per square metre
What can add cost?
- Removing old or failed insulation before replacement.
- Repairing cracks, wall ties or damp-related defects before cavity filling.
- Poor loft access, tanks, pipework or restricted working space.
- Loft boarding, hatch improvements and insulation protection.
- Irregular wall area or exposed elevations requiring a more cautious specification.
Loft versus cavity wall: why the price difference?
Loft quilt is usually a simpler installation over an accessible horizontal area. Cavity-wall work depends on external wall area, drilling pattern, material, access and whether the wall is suitable. That is why a semi-detached cavity-wall project can be several times the headline loft-insulation benchmark.
Sources
Cavity Wall Insulation Cost 2026
Used for property-type and per-m² cavity-wall benchmarks.
Loft Insulation Costs 2026
Used for current 270mm quilt-insulation examples by property type.
Frequently asked questions
How much is loft insulation for a semi-detached house in 2026?
A current benchmark for 270mm quilt insulation in a semi-detached home is about £825, before unusual access, removal or boarding work.
How much is cavity wall insulation for a 3-bed semi?
Property-size guidance currently puts a typical semi-detached cavity-wall insulation project around £2,700. Actual wall area, material and survey findings can change the quote.
How much does cavity wall insulation cost per m²?
Current guidance places glass wool around £25–£30 per m² and polyurethane foam around £30–£65 per m².
Can every house have cavity wall insulation?
No. The wall construction, exposure, damp risk and condition need to be checked first. A professional suitability survey is important before installation.