What does roof insulation cost in 2026?

Roof insulation in 2026 varies widely, and it comes down to one choice: do you insulate the unused attic floor, or the sloping roofs of the attic room itself? Insulating the attic floor is the fastest and cheapest measure — expect € 1,000 to € 2,500 for an average home. The insulation then lies loose on the floor of an attic you use for storage anyway; the heat stays in the lived-in floors below.

If you want to use the attic as a room, you insulate the roof slope from the inside instead. Insulating the sloped roof from the inside costs € 2,500 to € 8,000 per job (roughly € 50 to € 100 per m²), including the finish with boards or plasterboard. The difference from the attic floor is the labour: insulation goes against every roof surface, around the roof windows and dormers, with a neat interior finish afterwards.

If you have a flat roof above a living space, it can be insulated from the inside — the underroof. Insulating a flat roof from the inside is project work: expect roughly € 40 to € 90 per m², which for an average floor comes to € 1,500 to € 5,000 per job. Unsure where the heat loss is greatest? An insulation survey with thermal scan costs € 95 to € 250 and many companies offset it against a follow-up job.

Besides the chosen measure, three things move the price: the roof surface, the finish you want (leaving insulation visible is cheaper than boarding it up) and the shape of the roof — dormers, roof windows and valley gutters add fitting and cutting work. Randstad rates additionally run 10-20% higher. Note: this is about insulating from the INSIDE. Adding insulation on the outside during a re-roof is a roofer's job and falls outside this site. Request several quotes and set them against the price index; a national insulation subsidy (ISDE) also exists whose conditions change regularly — ask the installer about the current scheme.