Recycled plastic (polyester) loft insulation
Soft white rolls spun from recycled plastic bottles. Polyester insulation doesn’t itch, doesn’t mind damp and is easy to lay, which is why it is popular for DIY-friendly and awkward lofts.
| What it is | Polyester fibre, often made largely from recycled PET drinks bottles |
|---|---|
| Comes as | Rolls and slabs |
| Typical lambda | Around 0.035 to 0.044 W/mK |
| Usual depth | Similar to mineral wool |
| Handling | Non-itchy, low dust |
| Best for | Lofts where comfortable handling or moisture resistance matter |
What it’s like
Polyester insulation looks and feels a bit like the stuffing in a duvet. It doesn’t shed irritating fibres, so it is much more comfortable to install and to be around afterwards. It doesn’t absorb water, doesn’t rot and isn’t a food source for mould. Its insulating performance is in the same range as mineral wool, so you need a similar depth.
Pros
- No itching, little dust
- Gives a use to recycled plastic
- Shrugs off damp
- Durable and keeps its loft (its thickness) well
Cons
- Usually costs more than mineral wool
- Melts rather than burns in a fire; products are treated to meet fire standards, but it is not non-combustible
- Being plastic, it isn’t a natural material, which matters to some people
When it makes sense
If someone in the house reacts to mineral wool fibres, if the loft is cramped and fiddly, or if you want a material that won’t sag or get soggy. For a straightforward loft where cost matters most, mineral wool usually wins.
Thermal conductivity (the “lambda” value, in W/mK) tells you how well a material resists heat: the lower the number, the less thickness you need. Figures here are typical ranges; the product’s own declaration of performance gives the exact value.
Common questions
Is recycled plastic insulation safe?
Does it work as well as mineral wool?
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