The condensation problem of thermal insulation walls is becoming increasingly serious. The problem not only affects the performance of the thermal insulation layer and durability of the envelope structure but also increases the risk of mildew. To explore the condensation characteristics of thermal insulation walls and the anti-condensation effect of the vapour barrier in hot and humid areas in China, a coupled heat and moisture transfer model of a one-dimensional wall with temperature and relative humidity as the driving potential was established and verified. Taking the internal and external thermal insulation walls of EPS-Clay brick as an example, the relative humidity distribution of eight types of envelope structures with vapour barriers at three different interfaces or without vapour barriers was simulated. The results show that the best anti-condensation effect is provided by creating a vapour barrier outside of the wall (Interface 1 of internal and external thermal insulation walls). Therefore, in the high-humidity area represented by Guangzhou, the vapour barrier layer is recommended to be set at Interface 1.
Keywords Condensation; internal and external thermal insulation; coupled heat and moisture transfer; vapour barrier