In severe cold area, the exterior layers of envelope usually experience seasonal freezing /thawing due to cold climate in winter. However, it can 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 with the modeling method developed. 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 heat transfer coefficient of the modeled envelope in the first year winter is about 7% higher than that in the tenth year, which is taken as final hygral state.