Effect of heat and mass coupled transfer combined with freezing process on building exterior envelope

• The relations of some parameters are presented to close the governing equations.
• The changing of some envelope parameters with drying was analyzed.
• Effect of freezing process on building exterior envelope parameters was analyzed.

In cold severe area, the exterior layers of building envelope usually experience seasonal freezing/thawing in winter. However, it would lead to severe problems especially in the newly completed building. In order to analyze the drying of envelope on building initial use, the heat and moisture coupled transfer of building envelope in severe cold area Harbin, China was simulated. The modeled result was analyzed. It is concluded that the drying rate of the newly completed building envelope is significantly high in the first year, especially in the first few months. Insulation performance of the wall in the first winter is most serious due to the high initial moisture and freezing ice content in insulation layer. For the simulated envelope, the freezing of the moisture content especially that in insulation layer had notable effect on heat transfer coefficient (thermal resistance), and the maximum of modeled envelope heat transfer coefficient in the first year winter is about 7% higher than that in the tenth year, which is taken as final hygral state. Some parameters as apparent density, specific heat, average thermal diffusivity, heat storage coefficient and thermal inertia index, which were always considered as constants for a fixed building envelope are also changed with the heat and mass transfer of building envelope.