Home Insulation Cost UK 2026: What Installers Charge and How to Get It Free via ECO4
Written by Tom Ellis · Senior Trades Editor
Last updated: August 2026
Last updated: August 2026 · United Kingdom
Quick Answer
Home insulation in the UK costs £300–£600 for loft insulation, £400–£600 for cavity wall insulation, and £5,000–£15,000 for solid wall insulation (external or internal). Thousands of properties qualify for free insulation under the ECO4 scheme — primarily households on means-tested benefits or with a low EPC rating. Loft and cavity wall insulation pay back through energy savings within 2–5 years.
Home Insulation Costs at a Glance — UK 2026
| Insulation type | Typical cost (3-bed semi) | Annual saving | Payback period |
|---|---|---|---|
| Loft insulation | £300–£600 | £150–£300/yr | 1–3 years |
| Cavity wall insulation | £400–£600 | £150–£250/yr | 2–4 years |
| External wall insulation (solid walls) | £12,000–£18,000 | £200–£400/yr | 25–40 years |
| Internal wall insulation (solid walls) | £8,000–£14,000 | £200–£400/yr | 20–35 years |
| Floor insulation (suspended timber) | £500–£2,000 | Varies | Varies |
Loft Insulation Cost UK
The most cost-effective single insulation measure available. Heat rises, and in an uninsulated home up to 25% of heat loss occurs through the roof.
- Blown or batt mineral wool: Installed between joists. Fast to install (2–4 hours). Cost: £300–£600 for a typical semi-detached house. Recommended depth: 270mm (current Building Regulations).
- Loft with storage boards: Requires insulation below boards AND above (rigid insulation on counter-battens). More complex — allow £600–£1,200.
- Flat roof insulation: Internally fitted rigid board or externally as part of a re-roofing project. £1,500–£5,000 depending on area.
Cavity Wall Insulation Cost UK
Most UK homes built between 1920 and 1990 have a cavity wall. Installers drill small holes in the external mortar joints every 1–1.5 metres, inject mineral wool, polystyrene beads, or foam, and repoint the holes. Takes half a day with no internal disruption.
Cost: £400–£600 for a typical 3-bedroom semi-detached house.
Caution: Only install in walls with no signs of damp and in areas with average or low exposure to driving rain. Use a BBA-certified installer and confirm a pre-installation survey is conducted. The Cavity Insulation Guarantee Agency (CIGA) provides 25-year guarantees on approved installations.
Solid Wall Insulation Cost UK
Pre-1920 homes typically have solid walls (225mm brick or stone with no cavity). Much harder and more expensive to insulate — but essential for older properties to meet modern energy efficiency standards.
External Wall Insulation (EWI)
Rigid insulation boards fixed to the outside, covered with render or cladding.
| Property size | EWI cost |
|---|---|
| 2-bedroom terrace | £8,000–£12,000 |
| 3-bedroom semi-detached | £12,000–£18,000 |
| 4-bedroom detached | £18,000–£28,000 |
Internal Wall Insulation (IWI)
Rigid insulation boards or stud walls with mineral wool fixed to internal faces of external walls. Reduces internal room dimensions by 75–100mm per wall.
| Property size | IWI cost |
|---|---|
| 2-bedroom terrace | £5,000–£9,000 |
| 3-bedroom semi-detached | £8,000–£14,000 |
| 4-bedroom detached | £12,000–£20,000 |
ECO4: Free Insulation for Qualifying Homes
The Energy Company Obligation (ECO4) scheme requires large energy suppliers to fund energy efficiency improvements for low-income or fuel-poor households.
Who qualifies
- Households receiving means-tested benefits (Universal Credit, Pension Credit, Child Tax Credit, Housing Benefit, etc.)
- Properties with an EPC rating of D, E, F, or G
- Some local authority referral schemes cover households not on benefits if the property has a very low EPC rating
What's covered under ECO4
- Loft insulation
- Cavity wall insulation
- Solid wall insulation (external or internal)
- Heat pumps
- Solar panels (in some cases)
How to apply
Contact energy suppliers (British Gas, E.ON, EDF, Octopus, OVO, etc.) directly and ask for an ECO4 assessment. Alternatively, use the government's Simple Energy Advice service or a TrustMark-registered ECO4 installer. Only use TrustMark-registered installers— unregistered “free insulation” companies that cold-call have been involved in fraudulent schemes.
The Great British Insulation Scheme (GBIS)
Running alongside ECO4, the GBIS offers single-measure insulation grants to a broader group — including households not on benefits, if the property has an EPC rating of D or below and is in council tax band A–D.
Typical contribution: covers 50–100% of single-measure insulation (loft or cavity wall) in eligible properties. Check eligibility at gov.uk/great-british-insulation-scheme.
Installer Day Rates — UK 2026
| Installer type | Day rate |
|---|---|
| Loft insulation installer | £150–£250/day |
| Cavity wall injection specialist | £200–£300/day |
| External wall insulation specialist | £250–£400/day |
| Internal wall insulation (dry lining specialist) | £200–£350/day |
Most insulation work is quoted as a fixed price. Cavity wall and loft insulation companies typically price per job rather than per day. For ECO4 work, installers are paid by the energy company — you pay nothing if eligible.
Frequently Asked Questions
Does cavity wall insulation cause damp?
Poorly installed cavity wall insulation in properties with existing damp or in high-exposure areas can introduce damp problems. Use a BBA-certified installer, ensure a proper pre-installation survey is done, and check whether your wall is suitable. The Cavity Insulation Guarantee Agency (CIGA) provides 25-year guarantees on approved installations.
Can I install loft insulation myself?
Yes — top-up loft insulation using mineral wool rolls is one of the few genuinely practical DIY insulation tasks. Wear a dust mask, eye protection, and gloves. Ensure the existing insulation isn't asbestos (common in homes built before 1985 using loose vermiculite). Do not block eaves or ventilation points.
How do I know if my home has cavity walls or solid walls?
Measure the wall thickness. If the external wall is 220–270mm thick, it's likely a solid brick wall. If it's 280mm+, it's probably a cavity wall. Alternatively, check a nearby door or window reveal — cavity walls have a distinctive inner and outer leaf visible in the jamb.
Will insulation make my house feel smaller?
External wall insulation adds 80–120mm to the outside of the property — no internal impact. Internal wall insulation removes 75–100mm of internal space per insulated wall — noticeable in smaller rooms. Consider this before choosing IWI over EWI.
Is there VAT on insulation installation?
From April 2022, VAT on residential energy-saving materials (including insulation) was reduced to 0% in the UK. This means insulation installations are VAT-free, reducing costs by 20% compared to pre-2022 pricing.
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