Research On Moisture Transferring In The Exterior Thermal Insulation Composite Wall In Cold Zone

Energy saving is a long-term strategic task in the economic construction of our country. Reforming traditional wall to improve the wall thermal performance is an important measure to reduce the heating building energy consumption. With the deepening of the energy saving of our country, obviously, the single material wall can't meet the requirement of the standard for energy efficiency. The compound wall made of the structural material and high-efficient thermal insulator has already become the developing direction of thermal insulation wall. Exterior thermal insulation system has a lot of outstanding advantages comparing with other thermal insulation systems, especially, in cold zone and severe cold zone. Since the beginning of the 1990s, the exterior thermal insulation system was introduced to our country, and it has already been popularized and applied in the large and medium cities of northern. Mainly it is reflected in application of practical projects, but it is still very limited that the moisture state is studied in the exterior thermal insulation composite wall. This paper researches the thermal and moisture in polystyrene external insulation composite systems with rendering by experimental and theoretical method.Analyzing the mechanism of moisture transfer in the wall, this paper adopts the mathematics model based on vapor-penetrating theory which is suitable for the practical projects. Using this model to analyze the factors which affect the moisture transfer in the composite wall, there are indoor relative humidity and outdoor temperature and the vapor-penetrating resistance of the finish coat. The calculated results indicate that adopting average temperature of heating period to check the condensation inside the structure, may neglect the danger that the inside condense. I propose to use outdoor temperature and humidity of the monthly average.Through simulating winter temperature and humidity condition indoor and outdoor in the hot box, the work studies the moisture transfer inside the polystyrene external insulation composite wall of different finish coat. Comparing the hollow clay brick moisture content and the change of conduct heat coefficient of the wall in different period, the experimental result indicates that using the low moisture transfer coefficient finish coat such as glazed tile prevent indoor moisture transfer outwards through the wall and it is very dangerous to condensate in thermal insulation layer where there temperature gradient is great. Because of thermal insulation layer in moist state, heat transfer coefficient of the wall increase constantly.