Abstract
The moisture load in wall assemblies is typically considered as 1% of the Wind Driving Rain (WDR) load that is deposited on the surface of wall assemblies as specified in the ASHRAE-160 standard whereas this ratio has been shown to be inaccurate as compared to results derived from several watertightness tests. Accurate assessment of moisture loads arising from WDR can be obtained through the watertightness test during which different levels of WDR intensities and Driving Rain Wind Pressures (DRWPs) are applied to a test specimen and water that penetrates wall assembly can thus be quantified. Although many previous studies have included watertightness tests, only a few of these have attempted to correlate the moisture loads to WDR conditions as may occur in specific locations within a country. To improve the assessment of moisture loads for a vinyl-clad wall assembly, a wall test specimen was tested following a test protocol based on local climate data using National Research Council of Canada’s Dynamic Wind and Wall Testing Facility (DWTF). The use of this test protocol permitted quantifying the moisture load in the vinyl wall assembly when subjected to several different simulated WDR conditions. The moisture load was formulated as a function of the WDR intensity and DRWP which thereafter allowed evaluating the moisture load based on a given climate’s hourly rainfall intensity and wind velocity. Such work is particularly relevant considering that the intensity, duration and frequency of WDR events across Canada will in some regions increase due to the effects of climate change.
Highlights
The long-term moisture performance and durability of building façades are adversely affected by the moisture load, in particular those arising from the wind-driven rain (WDR) [1,2,3]
The first is to consider the moisture load as 1% of the WDR load that is deposited on the exterior surface of the wall assembly as specified in the ASHRAE-160 Standard [4]; and, the other approach is to directly measure the amount of water that has penetrated into a wall assembly during watertightness testing of a test specimen
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Summary
The long-term moisture performance and durability of building façades are adversely affected by the moisture load, in particular those arising from the wind-driven rain (WDR) [1,2,3]. This is relevant considering that the intensity, duration, and frequency of WDR events across Canada will in some regions increase due to the effects of climate change. In respect to run off, water can penetrate the exterior surface of the building facade when deficiencies are present and result in mold growth at the interior surface of the cladding [8] or decay of wood-based materials [9]
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