What does cavity-wall insulation cost in 2026?

For an average home you pay € 1,500 to € 3,000, including labour and materials. Floor insulation costs € 1,200 to € 2,800, crawl-space (ground) insulation € 800 to € 1,800 and an insulation survey with thermal scan € 95 to € 250. The facade surface drives most of the price: a terraced house has two facades to insulate, a detached home four.

That mainly depends on the construction year. Cavity walls came into use from roughly 1920; older homes often have solid walls without a cavity. Between about 1920 and 1975 the cavity was usually left uninsulated — the classic retrofit candidate. After 1975, insulation at build became increasingly common. The installer checks beforehand with a borescope inspection: if the cavity is wide enough, clean and dry, it can be filled.

The installer drills small holes in the mortar joints of the outer facade, injects the insulation material into the cavity and then neatly finishes the holes. Everything happens from the outside: nothing needs altering indoors and in most homes the work is completed in one day.

There is no single best material for every home: EPS beads, glass-wool flakes and PUR foam each have their own price, insulation value and application. Which one fits depends on the width and state of the cavity — the installer assesses that during the borescope inspection. Ask each quote for a short justification of the material choice, so you can compare them fairly.

Not without care. Damp patches, mould or penetrating damp first need an assessment of the cause: a filled cavity must not conduct moisture inwards. A serious company inspects the cavity and facade before filling and, where needed, advises repair first. So always mention known damp problems in your request.

Yes, a national insulation subsidy exists (the ISDE scheme). The conditions and amounts change regularly, so we deliberately quote no figures here — ask the installer about the current scheme and have the quote name which measures qualify.

Cavity walls can house protected species, such as bats. Nature-protection rules therefore require the cavity to be checked before insulating, with measures taken where needed. That can add lead time — ask the company at quote stage how it handles this check, so there are no surprises later.

No. This site focuses on the shell beneath and around the home: cavity walls, floor and crawl-space ground. Exterior roof insulation is roofers' work and insulating glass is window-frame work — for those you work with specialised companies from those trades.

Yes. Submitting a request costs nothing and commits you to nothing. You receive up to 3 quotes and choose yourself — or no one, that's fine too. Prices and payment are arranged directly with the insulation company.

Insulation companies in your region respond as soon as possible with a price indication. In autumn, before the heating season, diaries are fullest — whoever places a request well in advance compares calmly and schedules the work at the preferred moment.

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