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Usual measures: Breathable IWI, floor, sash upgrades, secondary glazing, draught-proofing. Watch-out: Moisture risk: breathable materials only.
Typical prices
Semi / end-terrace prices
Before grants · updated 11 October 2026 · a survey confirms the final figure.
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Consents and breathable materials
Listed buildings need listed building consent, conservation areas and Article 4 directions can restrict changes to the outside, and solid walls need breathable materials after a moisture risk check.Recommended

Wood-fibre, cork or hemp-lime systems that let solid walls stay dry.

Mineral wool or rigid board between the joists with an airtight membrane.

Sealing doors, windows, letterboxes, hatches, floorboards and unused chimneys — every home's quick win.

Mineral wool laid between and across the joists to 270–300 mm so heat stays in the rooms below.

Breathable lime render and lime plaster for older solid walls.

Natural insulation that handles moisture, popular with period owners.

Breathable boards and batts with good summer heat protection and low carbon.
Prices
| Measure | Semi / end-terrace |
|---|---|
| Loft insulation (new or top-up) | £600–£1,300 |
| Loft clearance and replacement | £1,500–£3,000 |
| Room-in-roof | £4,000–£9,000 |
| Cavity wall insulation | £1,200–£2,500 |
| Cavity extraction and refill | £3,500–£7,500 |
| Internal wall insulation (whole home) | £10,000–£20,000 |
| External wall insulation + render | £14,000–£24,000 |
| EWI with brick slip finish | £18,000–£32,000 |
| Re-render only (K Rend silicone) | £6,500–£12,000 |
| Suspended floor insulation | £1,500–£4,500 |
| Draught-proofing | £300–£800 |
| Whole-house fabric package | £22,000–£45,000 |
Indicative ranges for London and the South East, supplied and installed, including VAT, before grants. Updated 11 October 2026. A survey confirms your final price.
Up to fully funded; paid by energy suppliers per measure
Grant via local councils (£960m nationally in 2026/27)
Landlord-led bids
Saves 20% VAT
Varies
Eligibility depends on your circumstances and is confirmed by evidence and the funder or council.
0% VAT on energy-saving materials
Insulation, solar panels, batteries and heat pumps installed in homes in Great Britain are zero-rated for VAT until 31 March 2027. Windows and doors are not included.Houses
Begin your project
See a price range for your property type in two minutes, with grants and 0% VAT applied where they fit. A survey always confirms the final figure.