Modeling the thermal performance of earth-contact buildings, including the effect of phase change due to soil freezing

Abstract

A method for modeling the thermal performance of earth-contact buildings was developed that uses the ADINAT finite element thermal analysis program and hourly SOLMET solar/weather data available from the U.S. Commerce Department on FORTRAN compatible computer tapes. This study is the first to include the effects of phase change of water to vapor and freezing of the soil, which is important both in determining the thermal load on a building and in predicting structural frostheave damage, and for applications such as agronomy, meteorology, and solar ponds. A parametric analysis was performed of a typical two-dimensional earth-sheltered building geometry to determine model sensitivity to two variables: soil conductivity, and insulation placement. The results of the parametric study showed that: (1) the value used for soil conductivity in the model has a significant effect on the calculated thermal performance of the building, with results varying nearly linearly with conductivity; and (2) the placing of equal amounts of insulation either vertically along the inside surface of the wall, vertically along the outside surface of the wall, or horizontally, extending away from the building at the intersection of the building's wall and ceiling, results in nearly identical total yearly heat losses from the building. Though the above method was developed to model earth-sheltered buildings and basements, the method may be used, in general, to model the thermal performance of the earth contact part of any building, earth heat exchangers, buried electric cables or steam pipes, solar ponds, and a wide variety of problems in agronomy and meteorology.