What is the lifespan of loft insulation?

Loft insulation's not something you think about every day, right? But it's basically the unsung hero of your energy bills. Thing is, nothing lasts forever — not even the fluffy stuff in your attic. Depending on what you've got up there, you're looking at anywhere from 15 to 40 years before it starts phoning it in. Mineral wool and glass wool? They'll give you a solid 20 to 30 years. But spray foam or rigid boards? Those guys can push past 40. Here's the kicker though — even if the material hasn't technically "died," its performance can go downhill way sooner. Compression from boxes, moisture sneaking in, mice treating it like a hotel, or just gravity doing its thing over time. So knowing what you're working with isn't just nerdy trivia — it's literally money in your pocket.

How long does different types of loft insulation last?

Not all insulation ages the same. Some of it's basically invincible. Others? Bit more fragile. Here's the breakdown.

What are the signs that my loft insulation needs replacing?

Look, your insulation might not be dead yet, but it's probably not doing its job. You don't have to wait until it hits its theoretical expiry date — there's usually pretty obvious clues it's time for a change. Like...

• Visible damage: Water stains, mould, or damp patches on the insulation or roof timbers. Seriously — wet insulation loses up to 90% of its thermal performance. Ninety percent.
• Compression: Flattened insulation from old boxes or someone walking around up there? Its R-value's toast.
• Pest infestation: Droppings, nests, chewed bits — rodents and birds don't care about your energy efficiency.
• Increased energy bills: Noticed your heating bill creeping up for no obvious reason? That's often your insulation waving a white flag.
• Uneven temperatures: Cold spots in rooms below the loft, or weird drafts? Gaps and settling are the usual suspects.
• Age: If it's been 25 years since anyone touched it, it's almost certainly underperforming. Even if it looks fine.

Does loft insulation degrade over time?

Yeah, absolutely. All of it. But how fast and why? That's where it gets interesting. Fibrous stuff like mineral wool and cellulose? They physically break down. They settle, compress, and lose those tiny air pockets that actually do the insulating work. And moisture — that's the real enemy. It causes mould, rot in natural fibres, and thermal bridging that basically makes your insulation pointless. Spray foam and rigid boards are more chemically stable, sure, but they hate UV light. And if the surface they're stuck to moves or rots? Game over. Even in perfect conditions, nothing keeps its original R-value forever. The drop-off is slow though, so most people don't notice until their wallet starts hurting.

How can I extend the lifespan of my loft insulation?

You can actually keep your insulation working for way longer than you'd think. Just a bit of basic maintenance. Nothing crazy. Here's the checklist:

• Prevent moisture ingress: Check for roof leaks regularly. Fix broken tiles. And for god's sake, keep those ventilation paths (eaves, soffits) clear. Condensation is a killer.
• Avoid compression: Don't just chuck heavy boxes on top. Use loft boarding on stilts or raise the floor. Your insulation needs to breathe.
• Seal air leaks: Before you even think about insulation, seal gaps around pipes, cables, and chimneys with caulk or expanding foam. Drafts just suck the performance out.
• Pest-proof the loft: Seal any entry points bigger than 5mm with wire mesh or steel wool. Treated mineral wool is also less appealing to critters.
• Maintain ventilation: Don't block loft vents with insulation. Airflow stops moisture building up. It's that simple.
• Annual visual inspection: Once a year — preferably before winter — just have a look. Damp patches, mould, droppings, flattening. Takes five minutes.
• Top up when needed: If it's settled but still in good shape, just add a new layer on top (cross-laying, they call it). You don't always need to rip everything out.

Frequently Asked Questions