A transient non-linear coupled heat transfer problem with heat conductivity properties being dependent on moisture content has been studied for heterogeneous domain represented by a building exterior structure. Moisture content is considered as a variable parameter linked to material permeability and vapour transfer characteristics as well as amount of moist being condensed and evaporated. The solution to such problem has been obtained by using semi-analytical approach where the governing equations have been discretized by using finite element technique at the spatial domain, and analytically at temporal domain. Picard iteration method has been used for equation linearization. Based on a connection detail of three-layered exterior wall with floor slab, a sample problem has been solved. The results are compared with the results of similar but linear problem.

Keywords: non-linear transient problem, semi-analytical method, heat transfer, evaporation, condensation