Insulation

IN THIS GUIDE

Why insulation comes first

Insulation is the cheapest way to cut bills and the smartest first step before any heat pump or solar. A warmer, better-sealed home needs less energy to heat, so everything else you do works better and costs less to run.

Loft insulation

Topping up loft insulation to the recommended 270mm is one of the best-value upgrades: roughly £300–£600 and often £150–£250 a year saved in a typical house. If your loft is bare, the savings are bigger still.

Cavity & solid walls

Cavity wall insulation (homes built after about 1920 with a gap between the walls) costs around £500–£1,500 and saves a similar amount to loft insulation. Solid walls cost more — internal or external, £8,000–£15,000+ — but lose the most heat, so it is high-impact and often grant-supported.

Draughtproofing & floors

Draughtproofing doors, windows, floorboards and unused chimneys is cheap (£100–£300 DIY) and instantly more comfortable. Insulating suspended timber floors and using thick curtains help too. These small jobs add up.

Costs & savings

Most insulation pays for itself within a few years. As a rule: loft and cavity walls are quick wins (low cost, fast payback); solid-wall and floor insulation cost more but tackle the biggest losses. Do the cheap, high-impact jobs first.

Grants for insulation

The Great British Insulation Scheme (GBIS) and ECO4 can cover part or all of insulation costs for eligible households, based on income, benefits, or your EPC and council-tax band. See the grants guide.