1 June 2026

Cavity, floor or ground: which insulation do you choose first?

Three measures beneath and around the home, three price bands. What the choices mean for comfort, damp and order of work.

For homes built before 1975 the cavity wall is often the logical starting point: the largest surface of the shell, filled from the outside through small drill holes and completed in one day in many homes. For cavity-wall insulation expect € 1,500 to € 3,000 per home — provided the borescope inspection declares the cavity suitable: wide enough, clean and dry.

If cold feet and rising cold downstairs are your main complaint, the floor is the felt winner. With floor insulation (€ 1,200 to € 2,800) the installer works from the crawl space and insulates the underside of the ground floor — you notice the effect right where you live. It does require a passable crawl space; state what you know about it in your request.

Is the crawl space low, or is damp rising from the ground? Then ground insulation (€ 800 to € 1,800) is the practical choice: an insulating layer of chips or beads on the crawl-space floor that also slows the rising damp. With structural water in the crawl space the company should first advise on the cause — a filled cavity or insulated floor does not solve a water problem.

Combining pays: companies gladly take cavity, floor and ground in one job, since the van and the crew are there anyway. Roof and glass insulation are separate trades (roofers' and window-frame work) that you place with specialised companies. A national insulation subsidy (ISDE) exists — the conditions change, ask the installer about the current scheme — and the current bands per measure are in the price index.