Methodology and application of simulated wind-driven rain infiltration in building envelope experimental testing

One of the building envelope's functions consists of controlling rain infiltration into the back wall. However, the complexity of building envelope junctions is such that water may find its way past the weather barrier and even into the stud space, thus possibly causing damage to hygroscopic, iron-based, and other materials found within. Given that such failure behavior can be realistically expected, there is a need to devise methods to study the capacity of wall assemblies to deal with such failures, i.e., the ability of walls to sustain small quantities of water infiltration. To this end, a wetting methodology was developed to simulate driving rain infiltration for large-scale building envelope testing. The determination of the loading consisted of three steps: first, characterization of atmospheric wind-driven rain taking into account relevant factors, quantification of driving rain quantity and frequency impinging on a building facade, and finally estimation of the proportion of impinging wind-driven rain that may leak through a building envelope deficiency. Then, a water infiltration method was developed to reproduce the determined loading. The wetting methodology was applied to study the hygrothermal response of 17 large-scale wood-frame walls wetted by simulated rain infiltration, and an analysis of the suitability of the method through the moisture content results was performed. Last, possible means to refine the wetting method were reviewed.