Sumfoam is the first foamed polymer material with a homogeneous nanostructure, which can be produced under industrial conditions. The diameter of the foam pores is in the submicron range and the foam consists of more than 90 % air. The significant effect of nanofoam as an insulating material is based on the fact that reducing the pore size of a foam into the nanometer range leads to a significant reduction in thermal conductivity and thus to an improvement in insulating properties. This is known as the Knudsen effect. It states that below a pore size of about 70 nanometers, air molecules collide more frequently with the bars between the cells than with other air molecules, so that a directed heat flow is no longer possible.