The Short Answer
On our estimates, insulating the loft of a three-bed semi to 270mm costs about £500 to £1,200: £400 to £800 for a smaller home and £900 to £1,800 for a detached house. There's no VAT on it until 31 March 2027.
The Energy Saving Trust says loft insulation lasts around 40 years and pays for itself many times over. Topping up thin insulation costs less than starting from nothing, and some households can get it free.
Loft insulation prices
| Home | Laid to 270mm |
|---|---|
| Flat or small house | £400 to £800 |
| Three-bed semi | £500 to £1,200 |
| Four-bed detached | £900 to £1,800 |
How deep it should be
The Energy Saving Trust says current building regulations recommend at least 270mm of mineral wool, the minimum for new homes. When we checked in October 2026, it put insulating a loft from nothing at about £750 and topping up from 120mm to 270mm at about £600, in Great Britain. Topping up from 120mm saves about £17 a year by its figures. Measure what's there with a tape before you ask for quotes.
DIY or an installer?
The Energy Saving Trust says you can do it yourself if the loft is easy to get into, free of damp and not a flat roof: lay the first layer between the joists, and the second at right angles over them. Call in a professional for a flat roof, insulation along a sloping roof, a loft used as living space, or any damp or structural worries.
If you use an installer, choose a TrustMark-registered business and ask which competent person scheme they belong to.
Storage and condensation
Insulation changes how air moves through the roof. The Energy Saving Trust warns that without enough ventilation, condensation can cause damp, mould or rot in the roof timbers. If you want to store things up there, it advises boarding over a raised floor with the second layer of insulation underneath, leaving a small gap for ventilation. See loft boarding costs.
Free loft insulation and VAT
If you get certain benefits and live in private housing, the Energy Company Obligation (ECO) can help pay for insulation; owners need an energy rating of D to G, private tenants E to G. Apply through your council or an energy supplier. The current scheme, ECO4, runs until 31 December 2026. See ECO in full. The Great British Insulation Scheme closed on 31 March 2026.
In England, the Warm Homes: Local Grant can also pay for loft insulation for households on a low income (usually £36,000 a year or less), on certain benefits or in certain postcodes, in homes rated D, E, F or G. In Scotland, Wales and Northern Ireland, the Energy Saving Trust points to Home Energy Scotland, Nest and the NI Sustainable Energy Programme.
Installed insulation is zero-rated for VAT until 31 March 2027, then 5% from 1 April 2027.
Get loft insulation quotes
Loft insulation is priced by the loft area and what's there now.
Free, no obligation. We're paid by MyJobQuote when a tradesperson buys your job, never by you.
Frequently asked questions
How much does loft insulation cost?
On our estimates, about £500 to £1,200 for a three-bed semi laid to 270mm, with no VAT until 31 March 2027.
Is free loft insulation still available?
For some households. ECO can fund it if you get certain benefits and the home has a low energy rating, until 31 December 2026, and in England the Warm Homes: Local Grant covers lower-income households. The Great British Insulation Scheme has closed.
Is loft insulation worth it?
Yes for a bare or thinly insulated loft: the Energy Saving Trust says it lasts around 40 years and pays for itself many times. Topping up from 120mm saves about £17 a year by its figures.
How thick should loft insulation be?
At least 270mm of mineral wool, the Energy Saving Trust says.
Can I insulate my loft myself?
Yes, if it's easy to access, dry and not a flat roof: one layer between the joists and a second across them. Leave flat roofs, sloping roofs and lived-in lofts to a professional.
How we priced thisView sources (5, 4 official)
Rules come from the legislation and official guidance, read at source. Prices are our estimates: we check them against trade price data, retailer shelf prices and specialists' price lists, then build them up from their parts so the totals add up. Below are the sources behind the page; the trade price guides we only compare against aren’t listed. Where sources disagreed, we've said so. More on our method.
- IndustryRoof and loft insulation, Energy Saving Trust. Checked 16 Oct 2026.
- OfficialHelp from your energy supplier: the Energy Company Obligation, GOV.UK. Checked 16 Oct 2026.
- OfficialExtending the ECO4 end date (consultation outcome, updated 23 January 2026), GOV.UK. Checked 16 Oct 2026.
- OfficialApply for the Warm Homes: Local Grant to improve a home (England), GOV.UK. Checked 15 Oct 2026.
- OfficialEnergy-saving materials and heating equipment (VAT Notice 708/6), HM Revenue & Customs. Checked 16 Oct 2026.
