Abstract Testing of the actual properties of insulation materials is usually connected with the actual situation when measurement realization requires suitable weather conditions, for instance the winter time. The previous research [6] , in which measurements of polystyrene were conducted, was testing its thermal properties under actual conditions every 30 min, being directly dependent on the building environment where the insulation material was tested. Laboratory simulation of the actual application on the outside of the building to test the thermal properties of insulation materials can circumvent the dependency on the actual environmental conditions during the experiment. Here the actual thermal conductivity through the material of a specific thickness was tested using a new experimental measuring method. The method is based on generating an outside temperature of −18 °C using the Peltier module on one side of the block-shaped piece of insulation material. The methodology also enables testing of the internal thermal behavior of the material with the proper thickness as well as the shape of the material. The research results are especially useful when deciding on the effective thickness of the building’s insulating material; using statistical methods. The analytical expression of the insulation properties inside the material would also serve for that purpose.