Can you use old duvets as insulation in a loft?
Yeah, you could shove an old duvet up there if you're desperate, but honestly? It's a bad idea. They're not built for this. Proper loft insulation - mineral wool, PIR boards, cellulose - that stuff actually works safely. A duvet gives you a bit of a thermal barrier, sure, but it's missing fire resistance, vapour control, and it won't hold up over time. Let's get into why this is risky and what you should do instead.
What are the main risks of using old duvets in a loft?
Fire. That's the big one. Duvets go up like crazy if something sparks. Then there's moisture - they trap it, which means mould and rot in your roof timbers. And don't forget pests. Rodents and bugs love the organic stuff inside duvets. You're basically inviting them in for a free nest.
Is a duvet better than no insulation at all?
In a pinch, maybe. But even a thin layer of mineral wool blows it out of the water. A duvet's R-value is around 1.0 to 2.0 per inch. Mineral wool? More like 3.0 to 4.0. Plus, duvets compress over time - all that trapped air escapes, and suddenly you've got nothing. It's a temporary band-aid, not a fix.
| Material | Typical R-Value per Inch | Fire Resistance | Moisture Management | Lifespan |
|---|---|---|---|---|
| Old Duvet | 1.0 - 2.0 | Low (flammable) | Poor (absorbs moisture) | Short (months to a few years) |
| Mineral Wool (Rockwool) | 3.0 - 4.0 | Excellent (non-combustible) | Good (repels water, breathes) | Long (50+ years) |
| PIR Board (e.g., Kingspan) | 5.0 - 6.5 | Good (with foil facings) | Excellent (sealed, vapour barrier) | Long (50+ years) |
| Cellulose (Recycled Paper) | 3.5 - 3.8 | Moderate (treated with borates) | Moderate (absorbs, but treated) | Long (20+ years) |
How should you prepare a duvet if you must use it temporarily?
Alright, if you're absolutely stuck and need something for a few weeks, here's how to make it slightly less dangerous:
- Use a fire-resistant cover: Wrap that thing in fire-retardant fabric or a specialist blanket. Don't skip this.
- Ensure it is completely dry: Moisture is your enemy. Only use duvets that have been bone-dry and stored somewhere dry.
- Keep it off the floor: Lay it on a vapour-permeable membrane like Tyvek. Stops moisture wicking up from the ceiling.
- Monitor regularly: Check every few weeks for mould, dampness, or critters. If anything's off, yank it out.
- Plan a permanent solution: This is a stopgap. Order proper insulation ASAP. Don't get comfortable with it.
What are the best alternatives to old duvets for loft insulation?
If you want something that actually works and won't burn your house down, go with:
- Mineral Wool (Rockwool or Glasswool): Cheap, fireproof, great for sound and heat. It's the go-to for most DIY jobs.
- PIR (Polyisocyanurate) Boards: High R-value per inch. Perfect for loft conversions or tight spaces. Often has a foil vapour barrier built in.
- Cellulose (Blown-in): Recycled paper treated with fire retardants. Fills weird gaps nicely and is kinder to the planet.
- Sheep's Wool: Natural, breathable, handles moisture well. But it's pricey and might attract pests if not treated.
“Using old duvets in a loft is like using a cardboard box as a roof tile. It might keep some rain out for a day, but it is not a building material. The fire risk alone makes it a poor choice. Always use materials designed for the job.” — Mark Thompson, Chartered Building Surveyor
Can I put a duvet directly on top of existing insulation?
No, don't do that. You'll trap moisture between the layers - hello condensation and mould. Plus, it squashes the insulation underneath, making it worse. If you need more insulation, use something compatible like mineral wool or PIR board. And always keep a vapour control layer on the warm side.
Will a duvet attract mice or rats to my loft?
Probably, yeah. Duvets are warm and soft - perfect for nesting. The natural fibres like down, feathers, or cotton are chewable and comfortable. It's basically a welcome mat for rodents.
How long can I leave a duvet in the loft before it becomes a problem?
There's no safe time. Even a few weeks and it'll start soaking up moisture, especially if the loft's cold. It degrades quickly, loses its fluff, and becomes a fire hazard from day one. If you have to use one, pull it out after 1-2 months max and get proper stuff in.
Is a synthetic duvet safer than a feather one for loft insulation?
Synthetic's a bit less flammable, but it's still risky. Neither is safe. Synthetics melt when heated - dripping burning plastic everywhere. Feathers burn faster and smoke more. Both are awful choices.
Final Checklist for Loft Insulation
- Use materials with a minimum R-value of 3.0 per inch.
- Ensure all materials are non-combustible or fire-retardant treated.
- Install a vapour control layer on the warm side (facing the living space).
- Leave ventilation gaps at the eaves to prevent condensation.
- Do not compress insulation; it works by trapping air.
- Seal all gaps and cracks to prevent air leakage and pest entry.
Short Summary
- Not a safe solution: Old duvets are highly flammable and can accelerate a loft fire.
- Moisture and mould risk: Duvets trap moisture, leading to rot and mould in your roof timbers.
- Poor thermal performance: A duvet provides far less insulation than proper materials like mineral wool or PIR boards.
- Use proper insulation: For long-term safety and efficiency, choose mineral wool, PIR boards, or cellulose.
