XPS (Extruded Polystyrene insulation) needs an extrusion process. XPS’ closed-cell material has advantages in preventing water penetration of the insulation board, also gives a long-term durability and strength.
- Since it has a closed-cell structure, it is suitable for too moisty surfaces such as roofs.
- Has a remarkable strength so can be used under even very heavy structures such as concrete floors, slabs, foundations and underground works, etc.
- Has a very low thermal conductivity and so can provide a high thermal insulation performance
- Has lightweight, so easy to use and cut.
- 100% recyclable.
Both XPS and EPS provide good thermal conductivity performance. However, the air trapped in the voids in the EPS will conduct heat. A much higher density EPS board will be required to match the thermal performance of XPS insulation.
In general XPS has greater compressive strength than EPS. For EPS to achieve the same compressive strength as XPS, the density of the foam would need to be increased, often resulting in a greater thickness of the board being required.
Water vapour diffusion resistance:
EPS has a water vapour diffusion resistance of 30-70, whereas XPS reaches 80-250. Slightly more permeable to air and moisture, EPS is less resistant to water vapour than XPS. If you’re looking to insulate a space prone to humidity (e.g. floors, cellars and foundation walls), XPS is your best option.