What is EPS (airpop)?
EPS (expanded polystyrene), nowadays also called airpop, is a lightweight white foam plastic used as thermal insulation in construction. The material consists of about 98% air and only 2% polystyrene — hence the name airpop.
How is EPS made?
EPS is produced from small polystyrene beads, expanded using water vapour and pentane. The process has three stages:
- Pre-expansion — beads are inflated up to 40 times their original volume
- Conditioning — expanded beads stabilise in silos
- Moulding — under steam pressure, beads are fused together into blocks or boards
The characteristic white bead structure remains visible after moulding.
Application
EPS is used in virtually every part of a building:
| Application | Variant | Lambda (W/m·K) |
|---|---|---|
| Floor insulation | EPS-100 or EPS-150 | 0.036–0.038 |
| Cavity wall insulation | EPS beads | 0.033–0.038 |
| External wall insulation | EPS boards under render | 0.032–0.038 |
| Roof insulation | EPS boards | 0.036 |
Properties
- Lightweight — about 15 to 30 kg/m³, easy to work with
- Dimensionally stable — barely shrinks or expands
- Compression-resistant — depending on density, suitable under floors
- Moisture-resistant — absorbs very little water
- Affordable — one of the most economical insulation materials
- Recyclable — collected and reused
Caveats
EPS is combustible and must be covered with a non-combustible layer in façade applications. It melts at around 100 °C. UV radiation damages the material, so it should always be installed in a protected position.
Difference from XPS
XPS (extruded polystyrene) is denser, more compressive and more moisture-resistant, but more expensive. EPS is used more often for general insulation, XPS for floors below ground water level or for perimeter insulation.
Related terms
- Insulation
- PIR
- Mineral wool
- PS
- Cavity wall
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