Free Cavity Wall Insulation: Government Grants for 2026
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Unfilled cavity walls account for up to 35% of heat loss in your home. Cavity wall insulation is one of the most effective energy improvements — and if you qualify, it's completely free through government grant schemes. Most homes built between 1920 and 1990 have cavity walls that can be insulated.
How Much Could You Save?
What Is Cavity Wall Insulation?
Most homes built after the 1920s have two layers of brick with a gap (cavity) between them. Cavity wall insulation fills this gap with insulating material — usually mineral wool, polystyrene beads, or polyurethane foam — injected through small holes drilled in the outer wall.
The process is quick and minimally disruptive. A typical semi-detached house takes 2-3 hours. The drill holes are filled and colour-matched afterwards, leaving no visible trace.
Which Grants Cover Cavity Wall Insulation?
- ECO4 — UK-wide until December 2026. One of the most common measures installed under ECO.
- Warm Homes: Local Grant — England only. Covers cavity wall insulation as part of a whole-house approach.
- Home Energy Scotland — Grants and interest-free loans for Scottish homeowners.
- Nest (Wales) — Free cavity wall insulation for eligible Welsh households.
- NI Affordable Warmth — Northern Ireland Housing Executive scheme covering cavity walls.
Am I Eligible?
You may qualify for free cavity wall insulation if:
- Your home was built between 1920 and 1990 (likely to have unfilled cavities)
- You receive a means-tested benefit or have a household income under £36,000
- Your property has an EPC rating of D or below
- Your walls have an accessible cavity (typically 50mm or wider)
- Your council has identified your area under LA Flex criteria
How It Works
- Eligibility check — Use our free checker to confirm you qualify.
- Borescope survey — An installer inspects your cavity with a small camera to check it's suitable.
- Installation — Small holes are drilled in the outer wall, insulation is injected, holes are filled. Takes 2-3 hours.
- Quality check — The installer verifies even coverage and provides a guarantee certificate.
Cavity Wall Insulation: Key Facts
| Detail | Information |
|---|---|
| Suitable properties | Homes built 1920-1990 with unfilled cavities |
| Installation time | 2-3 hours |
| Typical cost (without grant) | £500-£1,500 |
| Annual savings | £270-£680 |
| Disruption level | Low — work is done from outside |
| Guarantee | 25 years (CIGA guarantee) |
| EPC improvement | Typically 1-2 band improvement |
Good to Know
If your walls are exposed to heavy driving rain, or the cavity is narrower than 50mm, cavity fill may not be recommended. The survey will confirm this.
Properties built before 1920 usually have solid walls with no cavity. You'd need external or internal wall insulation instead.
All cavity wall insulation installed under government schemes comes with a 25-year guarantee from the Cavity Insulation Guarantee Agency (CIGA).
Frequently asked questions
How do I know if my walls have a cavity?
If your home was built between 1920 and 1990, it almost certainly has cavity walls. You can also check by looking at the brick pattern — if all bricks are laid lengthways (stretcher bond), you have cavity walls. An installer will confirm with a borescope inspection.
Will drilling damage my walls?
No. Small holes (about 22mm) are drilled in the mortar joints, not the bricks. They're filled and colour-matched after installation. You won't notice them once finished.
Can cavity wall insulation cause damp?
When properly surveyed and installed, cavity wall insulation does not cause damp. Problems only arise if insulation is installed in unsuitable properties (e.g., those exposed to severe driving rain). The pre-installation survey specifically checks for this.
Is cavity wall insulation worth it?
It's one of the most cost-effective home improvements you can make. Savings of £270-£680/year on a measure that lasts 25+ years, and it's free if you qualify for a grant.
I rent my home. Can I still get this?
Yes, but your landlord must give written consent and may need to be involved in the application. Many landlords agree because it improves their property's EPC rating.
Find Free Cavity Wall Insulation in your area
See how Free Cavity Wall Insulation works in your area, including local council schemes, eligibility criteria, and nearby installers.
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