Types, costs, savings and installation — everything UK homeowners need to know about loft insulation. Independent, unbiased, updated for 2025.
Key fact: A significant amount of heat — often around a quarter — can escape through the roof if your insulation isn’t up to modern standards. Heat naturally rises, so without effective insulation in place, it escapes through your roof — increasing energy bills and reducing comfort in your home.
Up to 25% of a home’s heat escapes through the roof. For the millions of UK homes with no insulation or insulation below the current 270mm recommended depth, this represents hundreds of pounds per year literally heating the sky. Loft insulation is the single most cost-effective home improvement for most UK homeowners — with payback periods of just 1–4 years and product lifespans of 40+ years.
The economics are compelling at any energy price point. But at current UK energy prices, a standard semi-detached loft insulation upgrade typically delivers savings of £150–£250 per year from day one. Over the 40-year lifespan of the product, that represents £6,000–£10,000 in cumulative savings — against an upfront cost of £300–£600.
Quick check: Look into your loft. If you can clearly see the top of the joists, your insulation is below 100mm — significantly underperforming. Current recommendation is 270mm. A top-up is inexpensive and immediately effective.
Scored across 5 factors: cost, efficiency, lifespan, risk level, and installation complexity
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Check My Home in 30 Seconds →| Type | Cost (semi-detached) | Annual Saving | Payback Period | Lifespan | Score |
|---|---|---|---|---|---|
| Foil Insulation Recommended | £200–£600 | £150–£250 | 1–3 years | 25–40 years | 8.5/10 |
| Fibreglass (Mineral Wool) | £300–£500 | £100–£200 | 2–4 years | 40+ years | 7.5/10 |
| Loose Fill | £350–£600 | £100–£180 | 2–5 years | 20–30 years | 6.8/10 |
| Rigid Board (PIR) | £600–£1,200 | £120–£220 | 3–6 years | 30–40 years | 7.0/10 |
| Spray Foam ⚠ | £1,000–£2,500 | £100–£200 | 8–15 years | 20–30 years | 4.0/10 |
Spray foam warning: Multiple major UK lenders decline mortgages on homes with spray foam on roof timbers. Removal costs £2,500–£10,000. See our full risks guide before making any decisions.
Foil insulation scores 8.5/10 — our highest rated type. It uses reflective barrier technology to reflect radiant heat back into the property. Particularly effective in draughty lofts, installs quickly, and carries zero mortgage risk. For most UK homes, this is our first recommendation.
The most widely installed loft insulation in the UK (7.5/10). Laid between and over joists to 270mm depth. Excellent 40+ year lifespan and widely available from local installers. Ideal for straightforward, dry lofts with good access.
Never install spray foam on roof timbers without independent specialist advice. The mortgage and resale risks are well-documented and serious. Our scoring system rates it 4.0/10 for this reason alone.
Some UK homeowners qualify for fully or partially funded loft insulation through government schemes:
Our installer partners check your eligibility for all available funding as part of the free survey — at no cost or obligation.
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