General semi-analytical solutions for the steady-state heat conduction problems for circular and three-dimensional rectangular slab-on-grade floors with uniform insulation are presented. The soil temperature field, and the total slab heat loss are presented and analyzed using the Interzone Temperature Profile Estimation (ITPE) technique. A parametric analysis is conducted to determine the effect of thermal insulation U-value, slab size. and water table depth on the total slab heat loss. In particular. it was found that the total slab hear loss is independent of its shape bur is strongly affected by the slab size and thermal characteristics.