The total heat transfer through moist, porous building materials is the sum of a number of heat-transfer phenomena. This paper presents experimental data on heat transfer through specimens of moist aerated concerte and mineral fiberboard. The aerated concrete specimens with known initial moisture distributions were exposed to a temperture gradient which caused a redistribution of moisture which in turn changed the heat flow through the material. The changes were monitored by thermal probes, heat flowmeters, and thermocouples. The results of measurements were compared with calculations based on a simplified analytical model and with measurements made by other investigators. A second series of tests was made on a moist specimen of high-density mineral fiberboard to demonstrate the extent of the dependence of the total thermal resistance on the distribution of moisture in the material.