Thermal conductivity of insulations approached from a new aspect

In the literature, several definitions can be found for the thermal conductivity; however, many of them are not clearly explained. The easiest explanation is the following: the property of a material to conduct heat. It is evaluated primarily in terms of Fourier's Law for heat conduction. Nowadays, the examination of the thermal conductivity of building materials is very important both for the manufacturers and for the consumers. Nonetheless in real, confusing definitions and interpretations can be found regarding the exact meaning of the thermal conductivity of the materials. In physics and in engineering practice, the following appellations are used as heat conductivity, thermal conduction coefficient, design and declared values of the thermal conductivities as well as the effective thermal conductivity. In this article we would give an overview about the correct explanations of the above-mentioned values. At first thermal conductivity measurements of four different types of expanded polystyrene materials (EPS, 80, 100, 150, 200) will be presented by using Holometrix Lambda 2000 type Heat Flow Meter after drying them in a Venticell 111 type laboratory oven to changeless mass.