Which loft insulation is best?
For most lofts, mineral wool rolls laid between and across the joists are the best value. Blown loose fill suits awkward lofts, natural fibres suit older breathable houses, and rigid boards are for insulating the roof slope rather than the floor.
How do the main types compare?
| Type | Best for | Watch out for | Relative cost |
|---|---|---|---|
| Mineral wool rolls | Most lofts, especially if you want boarding | Itchy to handle; must not be squashed | Lowest |
| Blown loose fill | Low pitches, trusses, obstructions | Moves if walked on; not for boarded lofts | Low |
| Sheep's wool or wood fibre | Older homes, lime or lath ceilings | Costs two to three times more | High |
| Rigid PIR boards | Warm lofts and rooms in the roof | Needs the right build-up to avoid condensation | Highest |
Is spray foam a good choice?
We do not install it. Spray foam applied to the underside of a roof can trap moisture against the timbers if installed badly, and some mortgage lenders refuse to lend on homes with it. Insulating the loft floor with mineral wool avoids those problems at lower cost.
Related services
Sources: Energy Saving Trust: roof and loft insulation; Which?: loft insulation costs and savings; LABC: building regulation requirements for loft insulation; GOV.UK: extending the ECO4 end date, government response; GOV.UK: VAT on energy-saving materials (notice 708/6); Property Care Association: spray foam guidance.
