Residential Slab-On-Grade Heat Transfer in Hot Humid Climates

Abstract

Heat transfer through an uninsulated slab on grade is calculated using a simple method developed by Kusuda. The seasonal and annual slab loads are graphed as a function of annual average soil temperature, Tm, for a variety of floor system resistances, thermostat setting and soil properties. Factors affecting Tm are discussed. For a typical carpeted residence in the hottest U.S. climates, the cooling load due to the slab is about 5 million Btu per cooling season. In some climates heat transfer through an uninsulated slab can be beneficial. These benefits are larger if the residence is operated with energy conserving thermostat settings and the soil surrounding the slab has high conductivity.