Foam polymers are used as insulators in wall structures, improving the thermal protection considerably while reducing the amount of material required and saving heat in operating buildings; this provides improved thermal comfort, which is particularly important for the harsh conditions in the Far North. The hygroscopicity and the amount of unfrozen water W//u//w are major working characteristics of these for use under northern conditions, in addition to the thermophysical and mechanical parameters, a technique for determining water content in a foam phenol plastic is presented.