Local/global analysis of transient heat transfer from building foundations

In this paper, a novel local/global (L–G) analysis technique is developed to solve transient ground-coupled heat transfer problems. The presented (L–G) analysis approach combines analytical and numerical techniques to obtain solutions of building foundation heat transfer problems with significant localized thermal bridges. Even though simplified analytical solutions generally fail to account for thermal bridging in building foundations, they can be very useful when used as global solutions in the proposed (L–G) analysis technique. In this paper, the developed (L–G) analysis is shown to be an efficient and useful tool to evaluate transient heat transfer for slab-on-grade floor foundations. In particular, it is found that a CPU time reduction of about 90% can be achieved without loss of accuracy when the (L–G) analysis technique is compared to finite difference method. The developed (L–G) analysis technique is particularly useful in evaluating the effects of various design parameters of a slab foundation with minimal computational but can be easily extended and applied to various heat transfer problems in building envelope systems.