Thermal conductivity is a building material parameter. The lower the thermal conductivity, the better the insulating performance. The thermal conductivity of insulating materials is influenced by the cell gas – in the case of Neopor® and Styropor®, this is air – of the skeleton structure, of the matrix of the foam and, to a large extent, by the permeability with respect to heat radiation.

Thermal conductivity of white EPS as a function of the density, measured according to DIN EN 13 163.

The thermal conductivity of conventional EPS: good

The thermal conductivity of conventional white EPS, also known under BASF’s brand name Styropor®, is largely a function of the density of the finished rigid foam (Figure above).

The figure shows that white rigid foam made of EPS with a density of 15 kg/m³ reaches a thermal conductivity of about 0.037 W/m · K). Up until now, a reduction of the permeability to radiation and thus an improvement of the thermal insulation could only be achieved by raising the density, which is associated with higher costs.