Insulation ~ Expanded Polystyrene

Expanded Polystyrene insulation is made from small beads of polystyrene that are heated to expand them. To create boards, the beads are heated further to fuse the beads together. Boards are typical used in walls, roofs and floors. Polystyrene beads can be used as lose cavity fill in masonry walls.

Lose or in boards we’re all familiar with the white, squashy polystyrene balls that form the basis of this type of insulation.



  • Manufactured from petrochemicals so not sustainable and toxic when burnt.
  • High embodied energy.
  • Cheap.
  • Moisture tolerant and relatively durable.
  • Versatile and relatively easy to fit.

Typically has a thermal conductivity or K value in the range of 0.032 – 0.040 W/m.K. (Watts per meter Kelvin ~ lower value is a better result)

At 100mm thickness cost should be between £4 & £5 a square metre.