Which insulation is in your loft, and what goes wrong with it?
Every material fails in its own way. Here’s what to look for, and what we’d lay once the problem is fixed.
Illustration: loft insulation materials side by side
| Material | What goes wrong | Good for |
|---|---|---|
| Mineral wool | Flattened by storage, damp, soiled by pests | |
| Sheep’s wool | Costs more; treated against moths | Older homes; lofts prone to some moisture |
| Recycled polyester | Costs more than mineral wool | Lofts you go into often; people who dislike itch |
| Rigid boards | Gaps around the edges letting air past | Shallow joists, under a storage floor |
| Blown insulation | Drifting into eaves, blocking ventilation | Low, cramped or awkward lofts |
| Multifoil | Condensation if fitted without a ventilated gap | Rooms in the roof, tight spaces |
Whatever the material, it goes on the loft floor, between and over the joists. The only insulation we fix to the rafters is multifoil. We recommend a material in your quote.
- Mineral wool
- Mineral wool is in most British lofts. Why it flattens, gets damp or soiled, when it needs replacing and how we lay it so it lasts.
- Sheep’s wool
- Sheep’s wool insulation copes with moisture better than most and is pleasant to handle. When it suits older, damper lofts and what it costs to choose it.
- Recycled polyester
- Recycled polyester loft insulation: soft, clean to handle and unaffected by damp. When it makes sense after removing spoiled insulation.
- Rigid boards
- Rigid PIR boards cut between the joists where there’s little depth, such as under a boarded floor. Where they suit and how to fit them so they stay dry.
- Blown insulation
- Loose blown insulation for low, cramped or awkward lofts. Where it works, where it causes problems and what we check before using it.
- Multifoil
- Thin multifoil insulation fixed to the rafters, where a room in the roof or tight space needs it. How it’s fitted and how to avoid condensation.
Tell us what you’ve found. We’ll find the cause.
Describe the problem and we’ll look, explain it and quote the fix in writing. Free.