Study On Drying Characteristics And Its Effect Of Newly-Completed Building Envelope

China is in the time of fast developing of industrialization and urbanization. In 2005, the government showed that the existing building total area was about 40,000 million square meter, and 1800 to 2000 million square meters building area would increase every year in the next fifteen years. With the attention on human environment and energy crisis and increased need for energy-saving and indoor environment, more and more refined study was on the building envelope. Building envelope is a typical porous media, in which is full of moist air, liquid water or ice. The heat transfers in the moist porous building materials through a few different ways. The effect of moisture transfer on heat transfer and insulation performance of porous building envelope can not ignore.The main attention of the existing references about the heat and mass transfer of building envelope is on the simulation and study of heat and mass transfer of quasi-stable state building in hot and moist area. But little was on the drying of the new buildings, that is buildings with high initial moisture content, especially the buildings in cold serious area, in which no published reference seen. The wall system is an important component of building exterior envelope which affects the building performance in many ways: the moist damping on the building service life, the interior moisture release on the indoor air quanlity and the moisture infiltration on the building energy performance, etc. these questions would be more serious for new buildings due to the high initial moisture content.The heat and moisture coupling transfer of drying building envelope with multilayer composition in the cold serious area Harbin was simulated first time using Whitaker volume average method. The infiltration of liquid water and the freezing of moisture were considered. The moisture content gradient was used as mass transfer driving forces and the discontinuity effects of interface between porous materials with different pore size distribution was solved. The heat and mass conservation equations were built for different drying periods. The effect of indoor and outdoor climate condition, the vapor insulation and air layer beside insulated layer, the interior wallpaper and exterior glazed tile on the drying rate was compared and analyzed. The experimental study on the single layer porous building materials envelope was done in energy-saving laboratory of Harbin Institute of Technology, and the result was compared with simulated result.For the warm areas, the effect of building drying on indoor air quality can be minished through increasing ventilation rate. But for cold serious area, especially in winter, the ventilation rate is usually small due to the big energy consumption, so the effect on indoor condition would be more serious. The effect of building envelope drying on the indoor temperature and humidity was analyzed under the measured outdoor climate condition of Harbin. The integrated heat and moisture coupled transfer of the whole building was modeled. The effect of different indoor ventilation rate on interior moisture release and percent dissatisfied of warm respiratory comfort was discussed.The building envelope insulation performance of developed countries is about two to three times higher than our countries. It is imperative to achieve energy-saving buildings under the situation. The proposed international and internal energy-saving criterion to reply to the economy crisis did not take into account the effect of moisture transfer in building envelope. The estimation error on building energy performance due to the neglect of moisture infiltration affects the building energy efficiency more serious. In cold serious area, the heating load in winter has a big proportion to the whole building energy performance. The new building due to the high initial moisture content and insulation damping affects the building insulation performance. The effect of heat and moisture transfer on building energy, that is building energy consumption and air-conditioning moisture load, was studied in this paper.The drying performance of the new building envelope was studied comprehensively in this paper,which consummated the study on heat and moisture transfer of building envelope further. It will provide an imporant intruction for energy-saving and study of indoor air quality deeply.