Understanding and modelling future wind-driven rain loads on building envelopes for Canada

Abstract

Wind-driven rain (WDR) is the amount of rainfall that passes through a vertical plane due to its co-occurrence with wind, which can adversely impact the performance of building façades. Hygrothermal and durability analysis of façades require quantification of future WDR loads for a changing climate. This study evaluates projected changes to WDR loads across Canada for the end of century using regional climate model simulations for the Representative Concentration Pathway scenario 8.5. WDR loads are quantified in terms of omnidirectional and directional WDR amounts over periods of interest, which are relative indicators of WDR exposure and potential moisture content of absorbent surfaces, respectively. Furthermore, return levels of annual maximum WDR spell amounts, which are representative of the risk penetration through the façade, are also used to develop WDR risk category maps for Canada and specifically for 16 Canadian cities.Future projections suggest increases in WDR loads for Arctic Canada, due to increases in both rainfall and wind magnitudes, while for other regions with increased loads, it is mostly due to increases in rainfall. Results suggest a shift in the timing of the highest monthly WDR loads from summer to fall, which is suggestive of higher WDR penetration through wall systems, given the relatively low evaporation rate in fall compared to summer even in a warmer climate. Furthermore, the developed WDR risk category maps show changes to critical façade orientations with elevated risk in future climate. This information is crucial in the development of detailed guidelines to ensure climate-resilient buildings.