Insulation Cost Calculator
Mineral wool at £25–£45/m² fitted (£/U-value champion for loft floors). PIR boards at £45–£80/m² (best for rafter-level where every mm of headroom counts). Spray foam at £45–£70/m² (fastest fit, but mortgage-flagged on 4 of 6 major lenders). Sheep's wool & wood fibre at £60–£110/m² (eco…
Open the calculator →Price insulation in 30 seconds
2 steps, using the figures from our cost guide.
How this calculator works
Every figure in this calculator is the one published in the cost table on our insulation guide. Pick the option that matches your job and the calculator returns that published range, adjusted for your region - it does not model anything the guide does not already say.
That is deliberate. A calculator whose rates drift from the page it sits under is worse than no calculator, because two numbers on the same site disagree.
What it cannot know: the state of your roof and loft, which decides whether insulation is a simple job or the last step of a bigger one. Rolling insulation between and over the joists of a clear loft is the cheap end; insulating a room-in-roof, boarding over for storage, or dealing with existing damp and poor ventilation all cost more. Ventilation is the part people miss — insulate without it and you invite condensation. If the roof itself needs attention first, our roofing guide covers that, and a building survey is what flags damp or a failing roof before you insulate over it.
Published insulation costs (2026)
| Option | Typical 2026 cost | Notes |
|---|---|---|
| Mineral wool quilt | £25–£45 | |
| PIR board | £45–£80 | |
| Spray foam (closed cell) | £45–£70 | |
| Spray foam (open cell) | £35–£50 | |
| Sheep's wool | £60–£110 | |
| Wood fibre board | £70–£120 | |
| EPS / polystyrene board | £35–£60 | |
| Multifoil | £35–£60 |
These are the figures from our insulation cost guide.
Insulation calculator — FAQs
It uses the same published figures as the cost guide it sits under, adjusted for your region. It is a budgeting estimate, not a quote - only a site visit produces one of those.
Related cost guides
- Insulation cost guide — The full price guide
- All builders services — Browse the hub
- All BestBuilders services — Every trade we cover
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