A horizontal layer of expanded polystyrene foam (EPS) is widely used as a frost insulation of building foundations in the Nordic countries. The performance properties of the insulation depend strongly on the moisture level of the material. Experimental methods are needed to produce samples for testing the material properties in realistic moisture conditions.
The objective was to analyse the moisture loads and the wetting mechanisms of horizontal EPS frost insulation. Typical wetting tests, water immersion and diffusive water vapour absorption tests, were studied and the results were compared with the data from site investigations. Usually these tests give higher moisture contents of EPS than what are detected in drained frost insulation applications. Also the effect of different parameters, like the immersion depth and temperature gradient were studied.
Special attention was paid to study the effect of diffusion on the wetting process. Numerical simulation showed that under real working conditions the long period diffusive moisture absorption in EPS frost insulation remained lower than 1 % Vol. Moisture performance was determined experimentally as a function of the distance between the insulation and the free water level in the ground. The main moisture loads and the principles for good moisture performance of frost insulation are presented.