On Variability in Physical Properties of Molded, Expanded Polystyrene

When computer models are used for predicting field performance of moist insulation products, we must learn how to quantify the variability in measured properties. This is an issue of adequate material characterization. A description by the EPS type is not sufficient. By using additional elements of material characterization such as specimen density, one improves the precision of measurements of physical properties. In the case of thermal properties, a second element of material characterization, namely the coefficient describing attenuation of thermal radiation in the material (specific extinction coefficient) is also needed. In effect, variation in thermal properties of EPS products is fully accounted for when defining only a few parameters such as bulk density, specific extinction coefficient, and thickness and temperature of the specimen.