Insulation cost UK 2026
Loft insulation (270 mm) for a 3-bed semi is £450–£700 in 2026. Cavity wall insulation is similar. External wall insulation is the big one at £8,000–£15,000 for a whole house — but with ECO4 grants and 25–40 % heating savings, it often pays for itself.
How much does this cost in the UK in 2026?
The typical UK price range is £450–£22,000, with the average household paying around £2,200. Use the free calculator below to get a personalised estimate.
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What affects the cost?
- Insulation type — loft, cavity, internal, external, spray foam
- Area in m² to insulate
- Whether you qualify for ECO4 or Great British Insulation Scheme funding
- Existing insulation depth (top-up is cheaper)
- Scaffolding for external wall insulation
- Render or cladding finish on top of EWI
- Vapour control layer and ventilation upgrades
Cost breakdown
| Item | Low | High |
|---|---|---|
| Loft insulation 270 mm (3-bed) | £450 | £700 |
| Cavity wall insulation (3-bed) | £500 | £800 |
| External wall insulation (whole house) | £8,000 | £15,000 |
| Internal wall insulation (per room) | £800 | £1,800 |
| Spray foam loft (open-cell, 3-bed) | £2,500 | £5,000 |
Cost by UK region
Regional pricing varies by up to 50 %, mostly driven by labour rates. These multipliers apply to the base UK cost:
| Region | Multiplier | Typical cost |
|---|---|---|
| London | 1.35× | £2,970 |
| South East | 1.25× | £2,750 |
| South West | 1.10× | £2,420 |
| Midlands | 1.00× | £2,200 |
| North England | 0.90× | £1,980 |
| Scotland | 0.95× | £2,090 |
| Wales | 0.90× | £1,980 |
| Northern Ireland | 0.92× | £2,024 |
Planning permission?
Not required for loft/cavity; external wall insulation in conservation areas may need permission
How long does it take?
1–14 days typical, plus design and approvals time beforehand.
DIY vs Professional
Difficulty: Pro recommended. UK building regulations and Part P/Gas Safe rules mean most of this work must be done by registered professionals. Even where DIY is permitted, paying a pro is usually faster and more reliable.
How to save money
- Check ECO4 eligibility first — full grants are often available for benefits claimants
- Avoid closed-cell spray foam in lofts — most lenders will refuse mortgages on the property afterwards
- Combine loft top-up with re-roofing for best price
- External wall insulation can transform energy bills — but make sure the render is breathable
- Always upgrade ventilation when you insulate — sealing without ventilating causes damp
How to find a trusted tradesperson
Always get at least three written quotes. Use a vetted UK trade network for peace of mind:
- Checkatrade — vetted local trades with reviews
- MyBuilder — reviewed builders by job type
- Bark — get quotes from local pros
Or use the calculator above to get 3 free quotes direct to your inbox.
Frequently asked questions
How much can insulation save on energy bills?
Energy Saving Trust estimates loft insulation saves £225–£400/year, cavity wall £150–£300/year, and external wall insulation £400–£800/year for a 3-bed semi in 2026 prices.
Is spray foam insulation a problem when selling a house?
It can be. Many lenders (Nationwide, Halifax, Skipton) restrict mortgages on homes with closed-cell spray foam in the loft because it can hide roof timber rot. Open-cell foam is generally fine but always confirm with your lender.
Can I get free insulation in 2026?
Yes — through ECO4 if you receive certain benefits, or through the Great British Insulation Scheme if your home has an EPC of D or below. Check eligibility via gov.uk or Simple Energy Advice.
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Disclaimer: Prices are guide ranges based on 2026 UK market data. Get quotes from local tradespeople for accurate pricing.
Costs by type
Cavity Wall Insulation Cost UK 2026
£500 – £1,100
Cavity wall insulation for a typical UK 3-bed semi costs £500–£900 in 2026. Blown bead or mineral fibre…
External Wall Insulation Cost UK 2026
£8,000 – £22,000
External wall insulation (EWI) for a typical UK 3-bed semi costs £8,000–£15,000 in 2026 — including 90–120 mm…
Internal Wall Insulation Cost UK 2026
£800 – £2,500
Internal wall insulation (IWI) is the alternative when EWI isn't possible — typically £60–£110/m² installed. Best for solid-wall…
Loft Insulation Cost UK 2026
£450 – £900
Loft insulation (270 mm to current UK building regs) for a 3-bed UK semi costs £450–£700 in 2026.…
Spray Foam Insulation Cost UK 2026
£2,200 – £6,000
Spray foam loft insulation costs £30–£60/m² installed in 2026. While quick to apply, closed-cell foam can cause mortgage…
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