Guideline 3 - Insulation Systems / Extruded polystyrene (XPS)

Extruded polystyrene (XPS)

Insulation made of man-made materials

Extruded polystyrene (XPS) Extruded polystyrene (XPS) is made from the same material as expanded polystyrene (EPS), therefore the general properties are similar. The difference is in the production process, as XPS is made in a continued production process. The polystyrene balls are melted in the presence of an expansion gas (usually CO2), then the mass is extruded through a nozzle where the drop of the pressure causes the expansion of material. XPS is cooled down and cut. Opposed to EPS, XPS has a closed pore structure.

Typical final product is XPS boards. The perforation and cutting can be done at the construction site without losing the thermal properties of the material.

Usually the XPS boards are in white colour, but the more innovative have grey colour because of the graphite additives; these additives are applied to improve insulation performance.

Thermal properties are dependent on the temperature, moisture and mass density of the material. Typical values for thermal conductivity is 0.03 – 0.04 W/(m K), while the reference standard EN 13164:2012 is 0.033 – 0.035 W/(m K) for dry material at 10 °C.

Thermal conductivity of EPS increases 23 % (from 0.034 W/(m K) to 0.044 W/(m K)) in the case the moisture content in the insulation material increases from 0 vol% to 10 vol%.