Moisture Performance Assessment of Wood-frame Exterior Building Envelope Construction in China and Taiwan

In Canada and other parts of North America, traditional wood frame exterior building envelope construction is widely used and its ability to manage the exterior and interior moisture and thermal (i.e. hygrothermal) loads is well known from the field performance observations over the years. However, this type of building envelope construction is not traditionally used in China and Taiwan. At present, the Council of Forest Industries (COFI), an association of British Columbia forest industry partners, is promoting wood frame building envelope constructions and developing the market for the use of Canadian wood products in China and Taiwan. However, this is not possible without knowing the consequences and the ability of the wood frame building envelope assemblies to manage the hygrothermal loads in the climatic conditions of China and Taiwan. This is a long-term performance issue that becomes even harder to resolve when there is no comprehensive field performance data, as in this case. This paper presents result from a research project that investigated the hygrothermal (i.e. thermal and moisture) performance of the Canadian wood frame exterior building envelope construction practices in the city of Shanghai (China) and Taichung (Taiwan). This has been done using a two-dimensional hygrothermal simulation tool. Three exterior wall constructions and two roof constructions were exposed to the exterior climatic conditions of Shanghai and Taichung. The first set of simulations was conducted with a wall construction that has no air leakage. Thereafter, two wall constructions were also simulated with various levels of air leakage through the wall assembly. The outputs from the simulations have been analyzed with the help of a moisture response indicator called RHT index. Simulation results indicate the relative performances and suitability of the different wall and roof assemblies in Shanghai and Taichung. It is hoped that the results presented in this paper will help to develop moisture and thermal (i.e. hygrothermal) design guidelines for the Canadian style wood frame building envelope construction in China and Taiwan.