Heat loss to the ground from a building : slab on the ground and cellar

University dissertation from Byggnadsfysik LTH, Lunds Tekniska Högskola

Abstract: Heated buildings induce a heat flow from the building foundation into the ground. The topic of this thesis is the thermal process in the ground and, in particular, the heat losses from the building to the ground. Foundations of the three types slab on the ground, cellar, and crawl-space are dealt with. The crawl-space is treated in separate report. A reasonably complete theory for the thermal processes, and in particular the heat loss, is expounded. Dimensionless formulation, superposition technique, and analytical solutions for basic periodic and step-response components are used. The three-dimensional, steady-state heat loss component is obtained from numerical solutions. An accurate and manageable calculation method for heat losses to the ground has been developed. The method, which is based on both numerical calculations and analytical solutions, accounts for three-dimensional effects and the time-varying outdoor temperature in a proper way. The results from eight reports are used in the thesis: 1. Heat loss at the edge of a thermally insulated slab on the ground. Wiener- Hopf solution for periodic and step-change air temperature. Hagentoft C-E, Claesson J, Wallin N-0, 1985. 2. Temperature under a totally insulated slab on the ground due to variable ground surface temperature. Hagentoft, 1985. 3. Heat loss and temperature for a cellar of infinite depth. Periodic and step change air temperature. Hagentoft C-E, 1987. 4. Steady- state ground temperature and heat loss for a thermally insulated slab on the ground. Equal insulation thickness outside and inside the house. Hagentoft C-E, 1987. 5. Semi-analytical method for the temperature in the ground under a house with variable insulation thickness. Hagentoft C- E 1987. (Accepted for publication in International Journal of Building Science and its Applications.) 6. Analytical solution for the steady-state temperature in the ground at the edge of an insulaled cellar. Hagentoft C-E, 1987. 7. PC-program: Design rules for the slab on the ground and the cellar. Hagentoft C-E, 1988. 8. An analytical model for crawl-analytical model for crawl-space temperatures and heat flows. Steady-state, periodic and step-response components, Hagentoft C-E, 1986