Home Insulation Costs UK 2026: Full Price Guide & Calculator

What Each Job Costs

Costs are the Energy Saving Trust's for professional installation in Great Britain; solid wall costs are for a semi. DESNZ savings are its median for all homes applied to a semi using the median 10,574 kWh of gas a year, at 7.97p a kWh (our calculation). Paybacks use first-year savings at today's prices held flat: DESNZ says wall insulation savings hold up over five years, while loft savings are around a tenth lower by the fifth year. The draught proofing saving is for windows, floors and doors, a wider job than the cost, so its payback is rough. In Northern Ireland the Energy Saving Trust's costs are different (cavity around £1,000, a bare loft £1,100) and Ofgem's price cap doesn't apply.

Insulating a 3-Bed Semi From Scratch

Our sums of the Energy Saving Trust's figure for each job in Great Britain, for a home with none of it done: its loft and cavity figures are for a typical home, its solid wall figures for a 3-bedroom semi. If some of it is already done the total is lower; your EPC lists whether the walls, roof and floor are insulated.

Estimate Your Home

Pick your house type and age for the jobs that apply:

What It Saves, Measured

DESNZ's National Energy Efficiency Data-Framework compares the gas use of homes in England and Wales that had a measure installed with similar homes that didn't. Its median first-year savings: 12% for cavity wall insulation (2,191 homes), 3.2% for loft insulation (1,486 homes, top-ups included) and 17.3% for solid wall insulation (2,411 homes). The spread is wide: for each measure, at least a quarter of homes used more gas than the comparison group. DESNZ says the figures may understate the effect, partly because some households heat a better-insulated home to a higher temperature. Our insulation savings calculator applies them to your house type.

Loft Insulation

The Energy Saving Trust puts a bare loft insulated to 270mm at £750 and a top-up from 120mm at £600, saving about £17 a year, so a top-up takes about 35 years to pay back. DESNZ's measured 3.2% includes top-ups, and no separate measured figure is published for bare lofts. Our view: a bare loft saves more than that median and is worth doing, especially yourself; a top-up from a reasonable depth is mostly about comfort. Our loft insulation guide covers doing it yourself and spray foam in the roof.

Cavity Wall Insulation

The Energy Saving Trust puts cavity wall insulation at around £2,200 for a typical home in Great Britain. At DESNZ's measured median it saves a semi about £101 a year, so it pays back in about 22 years. The Energy Saving Trust says it may not suit a home that's exposed to extreme weather or flooding, in poor condition, at risk of rooms overheating, or with cavities narrower than 50mm. Our cavity wall insulation guide has costs by house type and what to check first.

Solid Wall Insulation

The Energy Saving Trust puts solid wall insulation for a 3-bedroom semi at around £12,000 on the inside and £15,000 on the outside. At DESNZ's measured median it saves about £146 a year, so on money alone it takes 82 to 103 years to pay back. It needs a grant, or another reason such as comfort or damp walls, to make sense. Our solid wall insulation guide compares internal and external, with costs by house type.

Floor Insulation

For a suspended timber floor, the Energy Saving Trust puts insulation at £1,400 to £2,500 and the saving at about £55 a year, so about 35 years at the middle of the range. Our floor insulation guide covers solid floors and doing it yourself.

Draught Proofing

The Energy Saving Trust puts draught proofing windows and doors professionally at around £250, and the saving from draught proofing windows, floors and doors at about £55 a year. Blocking an unused chimney saves about £45 a year, with a cap from about £150. Doing it yourself costs less.

How Long Insulation Lasts

The Energy Saving Trust says loft insulation installed correctly lasts around 40 years. Cavity wall insulation fitted by a registered installer comes with an independent 25-year guarantee from the Cavity Insulation Guarantee Agency (CIGA): a guarantee, not a lifespan. In our view, keep the certificate for when you sell. For solid wall insulation, ask what guarantee covers the work and who backs it if the installer stops trading.

What Can Go Wrong

Poor installation is the risk. The National Audit Office reported in October 2025 that DESNZ and Ofgem believe 98% of homes given external wall insulation under ECO4 and the Great British Insulation Scheme have major issues needing remediation (6% an immediate health and safety risk), and 29% of those given internal wall insulation (2%). Gov.uk tells anyone concerned about solid wall insulation fitted through a government scheme what to do. Our view: for any wall insulation, use an installer who works to PAS 2035 with a retrofit assessment first, and ask what guarantee covers the work.

Grants That Can Pay for It

• ECO4 (England, Scotland and Wales, until 31 December 2026): through energy suppliers or your council, for people on certain benefits in private housing (a home you own rated D to G, or a private rental rated E to G with the owner's permission) or living in social housing rated E to G; it can fund insulation and heating.
• Warm Homes: Local Grant (England): your council can pay for wall, loft and underfloor insulation if your home is privately owned (by you or your landlord, who may need to contribute), rated D, E, F or G, and your household income is usually £36,000 or less, or someone gets certain benefits, or you live in certain postcodes, where it has funding.
• Scotland: Home Energy Scotland offers homeowners grants of up to £1,500 for loft, cavity or underfloor insulation and up to £7,500 for solid walls, up to 75% of the combined cost and £7,500 in total, plus an optional interest-free loan; rural and island homes get £1,500 more. Warmer Homes Scotland can fund the work for households on certain benefits, or with someone over 75 with no working heating or terminally ill.
• Wales: Nest can fund insulation for eligible households (call 0808 808 2244); Green Homes Wales lends £1,000 to £25,000 interest-free to homeowners, without a means test.
• Northern Ireland: NISEP fully funds insulation for household incomes under £33,000 (single) or £40,000 (couple), and gives 40% off up to £650 a measure at any income; Affordable Warmth gives up to £7,500 (£10,000 for a solid wall home) to owner-occupiers and private tenants with incomes under £23,000, but not social tenants, and a landlord pays half.

The Great British Insulation Scheme closed on 31 March 2026.

Grants by nation

England | Scotland | Wales | Northern Ireland

What to Do First

Our view: draught proofing first, because it's cheap. Then fill empty cavities and insulate a bare loft, ideally with a grant. Leave solid walls until there's a grant or another reason. If a heat pump is coming, insulate before the heat loss survey so it's sized for the house you'll have; our insulate before a heat pump guide explains.