C028 -- Hygrothermal Simulation for Wooden Wall Assemblies in Medium-rise Building in Consideration of Rain Penetration into Vented Cavity

This paper focuses on the moisture behavior of wooden wall assemblies in medium-rise buildings when rain can penetrate the vented cavity. In medium-rise buildings, the temperature and vapor pressure in the vented cavity of the wall assemblies rise with increasing height of the air flow path by heating and humidification caused by solar radiation and rain penetration, respectively. Hence, the vertical temperature and vapor pressure difference in the cavity are assumed to be higher in medium-rise than in low-rise buildings. The impact of building height on the hygrothermal behavior was investigated in a multi-story hygrothermal simulation model developed by vertically laminating horizontal one-dimensional models. A ventilation network model was added for calculating the airflow rate in the vented cavity. Wall assemblies with typical configurations were simulated under the moisture-control criteria defined by ASHRAE 160. The simulations demonstrated that the temperature and vapor pressure increased in the cavity at higher locations of the wall assembly. When the airflow rate decreased in the cavity, notable internal condensation appeared on the vapor-barrier surface of the wall. The water-penetration rate from the exterior surface into the cavity significantly influenced the risk of moisture damage. The calculations also revealed the necessity of further studies considering the rain penetration on the medium-rise building.