How Much Does Home Insulation Cost in the UK? (2026)
Insulation costs vary enormously depending on type, property size and what grants you can access. Loft insulation is the cheapest and quickest win (often under £500). Solid wall insulation for older homes is the most effective but also the most expensive measure — though GBIS and ECO4 grants can cover most or all of the cost for eligible households.
Typical costs at a glance
| Type | From | To |
|---|---|---|
| Loft insulation (top-up) | £300 | £700 |
| Loft insulation (from scratch) | £500 | £1,200 |
| Cavity wall insulation | £400 | £1,200 |
| Solid wall — internal | £5,000 | £15,000 |
| Solid wall — external | £8,000 | £22,000 |
| Underfloor insulation (suspended) | £800 | £2,000 |
Prices are indicative 2026 UK averages. Get multiple quotes — prices vary by region, installer and property.
Types of insulation and typical costs
Loft insulation (£300–£1,200)
The cheapest and fastest-payback measure. A cold-roof loft is insulated to 270mm depth with mineral wool — takes a few hours. Often free for eligible households via the Great British Insulation Scheme or ECO4.
Cavity wall insulation (£400–£1,200)
Homes built after around 1920 typically have a cavity between the inner and outer walls. An installer drills holes and injects mineral wool, polyurethane foam or EPS beads. Usually takes half a day. Payback is typically 3–6 years. Often free for eligible households via GBIS.
Solid wall insulation (£5,000–£22,000)
Pre-1920s homes have solid walls with no cavity. External wall insulation (EWI) wraps the outside in insulation board and render; internal wall insulation (IWI) reduces room size slightly. Both are major works. EWI is more common (avoids internal disruption); IWI suits properties with decorative facades. Grants via ECO4 can fund this measure for eligible households.
Available grants
Both the Great British Insulation Scheme (GBIS) and ECO4 can fund insulation at little or no cost to eligible households. GBIS targets homes in council tax bands A–D with an EPC of D or below — no strict income test. ECO4 targets lower-income households on benefits. An installer can assess your eligibility before any work begins.
Common questions
What is the cheapest insulation improvement I can make?
Loft insulation is almost always the quickest win — it's cheap (£300–£700), fast to install, and has the shortest payback. If your loft has less than 100mm of insulation, topping up to 270mm can save £150–£300/year on heating bills.
How do I know if my home has cavity walls?
Homes built after roughly 1920 in the UK typically have cavity walls. You can check by measuring the depth of an external wall (around an open door or window) — 260mm or more suggests a cavity. Your EPC certificate may also note this. An installer can confirm with a borescope or drill test.
Will insulation affect my EPC rating?
Yes, significantly. Adding loft insulation can improve your EPC by one band (e.g. D to C). Cavity wall insulation often improves it by 1–2 bands. Solid wall insulation is even more impactful. A better EPC improves your mortgage options and makes the property easier to sell or rent.
How long does insulation installation take?
Loft insulation: 2–4 hours. Cavity wall insulation: 4–8 hours. Solid wall insulation is a bigger project — external insulation typically takes 1–3 weeks depending on property size.
Ready to get accurate quotes?
Prices vary — the best way to know what you'll pay is to compare quotes from MCS-certified local installers. Free, no commitment.