Loft Insulation Cost UK (2026)
Last updated 5 October 2026 · Prices based on the Ofgem price cap (October 2026 – December 2026)
A quarter of a home's heat can escape through an uninsulated roof. Mineral wool laid between and over the joists to 270mm is the standard approach and can be done as a DIY job or by an installer in a day.
Loft insulation cost payback calculator
At £700 net cost and £220 saved a year, it pays for itself in about 3.2 years.
- Net cost
- £700
- Payback
- 3.2 yrs
- 10-year saving
- £1,500
Simple payback = (cost − grant) ÷ annual saving, at today's price cap (26.32p electricity, 7.97p gas). Ignores future price changes.
Loft insulation cost by property type (0–270mm)
| Property type | Typical cost | Annual saving | Payback |
|---|---|---|---|
| Mid-terrace | £400–£600 | £150–£190 | 2–3 yrs |
| Semi-detached | £500–£750 | £200–£250 | 2–3 yrs |
| Detached | £700–£1,000 | £260–£310 | 2–3 yrs |
| Bungalow | £600–£900 | £230–£280 | 2–3 yrs |
What affects the cost
Loft size
Cost scales with floor area.
Existing depth
Topping up from 100mm costs and saves less.
Boarding
Raising boards for storage over 270mm adds £300–£800.
Access
Cramped lofts take longer.
Material
Mineral wool is cheapest; sheep's wool or PIR boards cost more.
How to reduce the cost
- Check your depth with a ruler
- Insulate the loft hatch and fit a draught strip
- Keep eaves vents clear for ventilation
- Insulate water tanks and pipes in the loft
- Check if you qualify for free insulation under ECO4 or GBIS
Frequently asked questions
How thick should loft insulation be?
270mm of mineral wool is the current recommendation.
Can I install loft insulation myself?
Yes, if the loft is accessible and dry. Wear gloves, goggles and a mask.
Is loft insulation free?
Some households qualify for free or discounted insulation via ECO4 or the Great British Insulation Scheme.
Can I still store things in my loft?
Yes, by using raised loft legs and boards so the insulation isn't compressed.
Does loft insulation cause condensation?
Not if eaves ventilation is kept clear.
Sources and methodology
Energy prices come from the Ofgem price cap for Direct Debit customers (GB average). Installation costs are typical UK ranges from installer quotes and industry guidance, rounded. Savings use today's rates and do not predict future prices.