The influence of soil moisture transfer on building heat loss via the ground

The primary aim of this work is to carry out a first assessment of the potential influence of the coupling between heat and moisture transfer in the soil and at the surface, on the heat loss from buildings via the ground. To that aim, results from coupled simulations – fully coupled transfer equations and complete surface heat and moisture balances – are compared to results from linear simulations. Notable deviations are observed, which are to be attributed to differences in both the surface heat balance and the heat transfers in the ground domain. The amplitude of the coupled surface temperature is roughly 20 % larger than its linear counterpart, while variation of the thermal properties, and advective heat transfer due to liquid moisture transfer effectively increase the heat flow in the soil domain. In a parametric study, it is shown that the coupling phenomena are influenced most by climate, while soil type and foundation width or thermal resistance do not have a substantial effect. The foundation’s shape, at the other hand, has a definite influence. In a conclusive part, the observed coupling influences are put in a larger perspective by comparing them to the accuracy of the European Standard on foundation heat loss. It is concluded that, with the current level of accuracy, the integration of coupling influences in standard methods cannot be defended.