Loft Insulation Cost: Prices, Savings and Payback

Energy Saving Trust publishes typical fitted costs and yearly bill savings for four house types in England, Scotland and Wales. The table uses its figures for an empty loft insulated to 270 mm, which it says is the minimum depth current building regulations recommend. We added a simple payback: the cost divided by the yearly saving.

These are typical costs, not quotes. Energy Saving Trust says its costs usually leave out surveys and extra work such as structural changes, electrical upgrades and ventilation improvements. It also says prices vary with the size of the house, how many installers work in the area and higher living costs in cities such as London.

Energy Saving Trust also warns that a simple payback ignores future energy prices, inflation and the life of the insulation, so treat it as a rough guide. It says loft insulation that is fitted correctly lasts around 40 years.

Many lofts already have some insulation. For a top-up from 120 mm to 270 mm, Energy Saving Trust gives typical fitted costs of £500 to £800 and savings of £13 to £35 a year. The first 120 mm does most of the work, so the extra depth saves far less.

On bill savings alone, a paid top-up from 120 mm takes 23 to 38 years to pay back at these figures, against a life of around 40 years for loft insulation. A DIY top-up costs only the rolls and safety kit, so the sums look much better if you can do it safely.

If your loft has less than 120 mm, the saving falls somewhere between the two tables. Energy Saving Trust does not publish figures for other starting depths, so measure what you have and ask installers to quote for your real depth.

The savings depend on energy prices. Energy Saving Trust’s data page lists the average prices behind its figures, including 6.5p per kWh for gas in Great Britain, based on an average of recent Ofgem price cap periods. That page was last updated on 22 September 2026.

Your own saving will differ. It depends on the size of the house, how warm you keep it, your heating system and your tariff. Homes heated another way, such as by oil or electric heaters, pay a different price per kWh, so the money saved changes too. Northern Ireland has its own figures on the same page, because the Ofgem price cap does not apply there.

If the loft is dry, easy to reach and has regular joists, Energy Saving Trust says you can lay mineral wool rolls yourself: one layer between the joists and a second layer at right angles across them. The cost is then the rolls plus safety kit. We do not quote roll prices because they change often. Count the rolls with our calculator and multiply by the price your supplier shows on the day.

The table comes from our UK loft insulation calculator with 100 mm deep joists and the 270 mm target. An empty loft uses a 100 mm roll between the joists and a 170 mm roll across them. A loft with 120 mm already in place needs one 150 mm layer across the joists. Each layer rounds up to whole rolls, so an empty 40 m² loft needs 8 rolls in all.

Add crawl boards and the kit the roll maker’s installation guide recommends: gloves, a mask rated FFP1 or higher, overalls and safety glasses. If you want to store things in the loft, do not squash the insulation under boards. Energy Saving Trust says to raise the floor and leave a small air gap, which adds to the cost.

Two funded schemes have ended or are ending. The government’s response on GOV.UK confirms that the Great British Insulation Scheme ended on 31 March 2026 and that ECO4 ends on 31 December 2026, with no new supplier scheme to replace it.

In England, the Warm Homes: Local Grant pays for upgrades, including insulation, for low-income households in privately owned homes with an EPC rating of D to G. It is run through councils and funding varies by area, so ask your council. In Scotland, Energy Saving Trust points to Home Energy Scotland, in Wales to Nest, and in Northern Ireland to the Northern Ireland Sustainable Energy Programme.

Energy Saving Trust suggests using a TrustMark registered installer, asking which Competent Persons Scheme they belong to and getting at least three quotes. Ask each installer the same questions: what depth they will fit, whether old insulation stays, whether they will check ventilation and whether boarding or hatch work is included.

Fix damp first. Energy Saving Trust says damp problems must be fixed before any insulation goes in, because insulation makes the loft space colder and condensation more likely. Flat roofs, rooms in the roof and insulation at the rafters need a professional.

Measure the loft floor area and the depth already there before you compare quotes or buy rolls. Check the Energy Saving Trust figures again on the day you decide, because they are updated, and note the date you checked them.

Get each quote in writing with the depth, product, area and extras listed. If the installer finds damp, poor ventilation or wiring that needs work, ask for it as a separate price so the quotes stay comparable.