The difference between EPS and XPS insulation … is in the detail

difference XPS insulation and EPS insulation


Whether or not a building complies with today’s increasingly stringent energy standards greatly depends on the type of insulation used. XPS and EPS are two popular insulation materials, each with their specific qualities. This article provides an overview of the differences between both materials, enabling you to select the best type of insulation material for your project.

What is XPS insulation?

XPS (Extruded Polystyrene) is available in rigid insulation boards. The boards have a closed cell structure and come in various compressive strengths, which makes them ideal for numerous applications. For example, XPS boards with a high compressive strength – such as XPS 500 and XPS 700 – are particularly suitable for insulating rooftop car parks and parking garages.

What are the advantages of XPS insulation?

Extremely resistant to moisture, XPS is the perfect insulation material for inverted roofs. In addition, XPS is an ideal insulation material for foundation walls. Moreover, XPS is resistant to mould, lightweight and easy to apply without irritating the skin. And did you know it is 100% recyclable as well?

Indeed, XPS insulation is an eco-friendly choice. The product benefits from BREEAM A rating. This ensures that specifiers can be sure of scoring with BREEAM points. XPS is also approved by the Green Guide to Specification.

What is EPS insulation?

EPS (Expanded Polystyrene) is a light-weight foam product. One cubic meter of EPS contains about 10 million beads. Each count approximately 3,000 cells which are closed off and filled with air. EPS is, in other words, composed of 2% polystyrene and 98% air. Since still air is the best thermal insulator, EPS makes for an excellent insulation material.

What are the advantages of EPS insulation?

EPS is very budget-friendly, lightweight and easy to process. While usually white, the material is also available in grey, and the insulation capacity of the latter is even better than the first. Finally, because EPS consists of only one type of material, it is easy to recycle.

Different types of EPS

EPS has been a popular insulation material for more than fifty years. There are three types available:

  • Cut-to-size boards, such as SOPREMA’s NEOSTIR CL 100, which are ideal for insulating flat roofs.
  • Pressed boards in a mould, such as NEOSTIR 029.
  • Loose pearls for post-insulating cavity walls.

What is the difference between EPS and XPS?

Both EPS insulation and XPS insulation guarantee excellent thermal conductivity. However, there are two important differences:

  1. Compressive strength: because XPS has a higher cell density, it is available in higher compressive strengths than EPS.
  2. Water vapour diffusion resistance: EPS has a water vapour diffusion resistance of 30-70, whereas XPS reaches 80-250. EPS is slightly more permeable to air and moisture, whereas XPS is less resistant to water vapour. Therefore, if you’re looking to insulate a humid area (e.g. floors, cellars and foundation walls), XPS is your best option.

Do you have any questions about SOPREMA’s innovative insulation solutions? Don’t hesitate to contact us!