How long does loft insulation last?
Good loft insulation lasts decades — but not forever, and not in every condition. Here's what to expect.
Quality mineral wool loft insulation, properly installed, typically lasts 40 years or more. It doesn't "wear out" in normal use — but a few things can shorten its effective life.
What reduces its lifespan
- Moisture and leaks — damp insulation loses performance and should be replaced.
- Compression — boards or storage laid directly on it flatten it and reduce its effectiveness.
- Disturbance — work in the loft can shift and gap it over time.
- Pests or contamination — occasionally an issue in older lofts.
When to top up or replace
If your insulation is thin (under ~270mm), patchy, damp, or decades old and compressed, topping up or replacing it restores performance. Newer homes may just need a top-up to current depth.
Not sure what condition yours is in? Book a free survey.
How to protect its lifespan
A few simple habits keep loft insulation performing for decades. Avoid crushing it with boxes or boarding laid straight on top — if you want storage, use raised loft boarding that sits above the insulation. Keep an eye out for roof leaks and fix them promptly, since damp is the main enemy. And if you ever have work done in the loft, make sure the insulation is put back evenly afterwards.
Signs it's time to refresh
- Visible damp, staining or a musty smell in the loft.
- Insulation that's flattened, patchy or below the joists.
- Rooms below feeling colder than they used to.