How much does insulation cost in 2026?
Loft insulation is the cheapest: the Energy Saving Trust puts it at £750 to lay 270mm in a bare loft and £600 to top up a thin one. Cavity wall insulation costs about £2,200 for a typical home. Solid wall insulation is the most expensive, about £12,000 inside or £15,000 outside for a typical 3 bed semi. Larger homes cost more. Many households on lower incomes can get loft and cavity insulation free through ECO4, which ends on 31 December 2026, or a Warm Homes: Local Grant from their council in England, where the council has funding.
See what each measure costs and saves for a detached house, semi, terrace, bungalow or flat in insulation cost by house type.
The savings we show are what homes measurably saved: the government compared gas use before and after in thousands of real homes. The median was 12.0 per cent for cavity wall insulation, 17.3 per cent for solid wall and 3.2 per cent for loft insulation, top-ups and bare lofts together. We apply those to your home's own fuel use, so a detached house saves more than a mid-terrace, and oil or LPG homes save more pounds than gas homes because their fuel costs more. These savings are lower than most calculators show, because many homes were under-heated before and take part of the gain as warmth.
Should I insulate before installing a heat pump?
Yes, almost always. Heat pumps work best in well-insulated homes because they operate at lower temperatures than gas boilers. Better insulation means you need a smaller heat pump (lower cost), the heat pump runs more efficiently (lower bills), and your home stays comfortable at the lower flow temperatures. Our EPC improvement planner can show you the most cost-effective order of improvements for your home.
Types of insulation explained
Loft insulation
The simplest and most cost-effective upgrade. The recommended depth is 270mm of mineral wool. If your loft is easy to access and you are comfortable working at height, this is a common DIY project. Professional installation takes a few hours for a typical home.
Cavity wall insulation
Suitable for homes built after the 1920s with unfilled cavity walls. An installer drills small holes in the outer wall, injects insulation material, and seals the holes. The Energy Saving Trust says it takes about two hours for an average home with easy to reach walls.
Solid wall insulation
For older homes, mostly built before the 1920s, with solid walls (no cavity). Available as internal insulation (boards fitted to interior walls, reducing room size slightly) or external insulation (cladding applied to the outside of the building). Both are effective but significantly more expensive and disruptive than cavity or loft insulation.
Frequently asked questions
How much does loft insulation cost in 2026?
The Energy Saving Trust puts it at about £750 to lay 270mm in a bare loft and £600 to top up an existing layer. Many households on lower incomes can get it free through ECO4 until 31 December 2026, or through a Warm Homes: Local Grant from their council in England, where the council has funding.
Is cavity wall insulation worth it?
Usually, and especially if a grant pays for it. Homes the government measured used a median 12.0 per cent less gas after cavity wall insulation, about £105 a year for a 3 bed semi on gas. At a typical £2,200 that is a long payback at full price, which is why most cavity insulation is grant funded. Get a survey first, because some exposed or damp walls are not suitable.
Can I get free insulation in the UK?
Yes, if you qualify. ECO4 funds insulation for many households on means-tested benefits or lower incomes until 31 December 2026, and councils in England with funding run Warm Homes: Local Grants. The Great British Insulation Scheme closed on 31 March 2026. Our grant checker shows which you could get.
Does insulation improve my EPC rating?
Yes. How much depends on the home and what it already has; our EPC improvement planner estimates it for yours.