Wind-driven rain and its impact on building envelopes

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The effectiveness of the building envelope to resist climatic loads determines the performance and durability of the building, its energy consumption, and the extent to which its net-zero/plus energy status can be achieved. Failures in building envelopes account for over 50% of building failures. Moisture intrusion by wind-driven rain and runoffs is the major source of moisture causing many building envelope failures, and often results in costly repairs, such as the case with Vancouver leaky condominium. The building envelope's capacity to manage moisture, especially wind-driven rain (WDR) and rain penetration, determines its long-term durability. **The goal of this research is to advance the understanding of WDR and runoff loads and their impact on building envelopes, to develop design tools, and to generate design guidelines for delivering energy efficient building envelopes with long-term durability. The proposed research will help consolidate a body of knowledge on the hygrothermal performance of building envelope systems subjected to WDR and rainwater runoff by i) investigating the WDR load and resulting runoffs on building envelopes in three different geographic regions in Canada, (ii) examining the role of overhangs on reducing the amount of WDR on building façades, and (iii) investigating the impact of wind-driven rain on the hygrothermal response of highly insulated wall assemblies. **The proposed research involves a balance between laboratory and field measurements, and modeling and simulations. The methodology will include: i) quantifying the effectiveness of overhangs on reducing WDR on building façades through field measurements and CFD modeling; ii) establishing rainwater runoff on building façades through laboratory and field measurements, and modeling; iii) developing a stochastic approach to model the hygrothermal responses of wall assemblies, and iv) developing a design tool for managing moisture damage risks in highly insulated wall assemblies by generalizing the results obtained in this study. **The proposed research program will advance the fundamental understanding of WDR and runoff as design loads and best practices by providing design tools and guidelines for delivering high performance building envelopes. Providing designers with guidelines and tools to better assess WDR loads and durability risks will enable them to make more informed choices among the numerous wall assemblies commonly accepted as best practices, resulting in improved consistency and reliability of building designs, especially with the higher energy efficiency demand. Ensuring long-term durability of energy efficient building envelopes will contribute to Canada's national objectives for the reduction of GHG emissions. This research will provide excellent opportunities to train HQPs.