Laboratory tests conducted on building assemblies to assess their resistance to rain penetration are commonly conducted by exposing the assemblies to air pressure differentials and water sprayed onto the outer surface to simulate wind-driven rain. The two primary test parameters are magnitude of air pressure differential and water spray rate. To assess the appropriateness of current standards for testing window assemblies exposed to real weather conditions in Metro Vancouver’s unique temperate rainforest climate, measurements of hourly wind-driven rain observed at building sites in Metro Vancouver are used to compute corresponding test conditions. Analysis of the observed site data leads to an expression for catch ratio as a function of wind speed. To establish a statistical basis for computing test conditions for specific return periods, the site data are linked to 25 years of average hourly historical data collected by Environment Canada from 1981 to 1996 at the Vancouver International Airport. Based on an extreme distribution analysis of wind speed and driving rain intensity, the water spray rate and air pressure differential corresponding to 10- and 20-year return periods are computed and compared to current standards. Results suggest that the standard for the intensity of rain impinged on window surfaces meets or exceeds measured conditions corresponding to a 20-year return period and are adequate for Metro Vancouver’s climate.
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