Experimental investigation of the wetting and drying potentials of wood frame walls subjected to vapor diffusion and wind-driven rain loads

This paper aims to study the effects of wind-driven rain load and vapor diffusion on the hygrothermal performance of wall systems in a wet and mild climate through a field experimental study. In the study, four test panels with a combination of vapor barrier and capillary break are manufactured, instrumented and installed in a field experimental facility. The wetting and drying potentials of the test panels in response to a predominately vapor diffusion and a wind-driven rain load are discussed based on the analysis of 15 months of measurement data. The experimental result shows that, in a yearly basis, the wetting and drying rates of a wall without a capillary break are about two times higher than that of the wall with a capillary break. While the wetting and drying rates are comparable in a wall system with a vapor barrier, the drying rate is 38% higher than the wetting rate in a wall with no vapor barrier. In general, a wall with no vapor barrier wets and also dries faster than a wall with a vapor barrier. For the wall types and climate considered in this paper, the wetting rates of walls with a predominately wetting mechanism of vapor diffusion and wind-drive rain load are comparable. In general, the experimental data suggest that even in a mild climate, vapor diffusion is a critical moisture load with comparable effect that wind-driven load induces.