Heat loss to the ground from a building—II. Slab on the ground

The heat flow to the ground from a rectangular slab with an even thermal insulation is analysed. The steady-state heat loss factor is given in complete diagrams for any ratio between length and width of the slab and for any constant insulation of slab and ground surface. A two-dimensional edge approximation for time-dependent heat loss at the perimeter of the slab is introduced. New analytical solutions for the edge heat loss due to periodically variable outdoor temperature or a step change in the outdoor temperature are presented. The effect on the heat loss due to different variations of the outdoor temperature is easily analyzed with these solutions. For example, daily periodic variations can certainly be neglected. Based on this, simple design rules for the heat loss during a heating season and the peak effect are given.