Volume 2, Issue 10 (November 2005)
A Review of Climate Loads Relevant to Assessing the Watertightness Performance of Walls, Windows, and Wall-Window Interfaces
When assessing a wall assembly's ability to manage rainwater and control rain penetration, the two key climatic elements to consider are wind speed and rainfall intensity. However, of significance to rain penetration is the effect of wind-driven rain on the building cladding — that is wind coincident with rainfall. When water is present at openings in the cladding, water is driven into the layers of the assembly by the action of wind. Paths providing a direct line from openings in the cladding to inside the assembly offer particularly vulnerable points for water entry. Performance testing helps determine the location of vulnerable locations in a wall assembly and the test loads at which penetration occurs, and it possibly relates the amount of entry to specific details and simulated climate effects. Undertaking watertightness performance tests requires knowledge of extremes in wind-driven rain or specifically the occurrence and level of extreme rainfall events for locations of interest. A review of climate information on wind-driven rain is provided, and its relevance to assessing the watertightness performance of walls, windows, and wall-window interfaces is discussed. Values of rainfall intensity, duration, and frequency or occurrence are given, emphasizing the level of significance of these variables to different North American climates.