| Abstract | Wind-driven rain (WDR) is the main moisture source that affects the hygrothermal performance and durability of building envelopes. Therefore, the quantity of wind-driven rain impinging on the surface of buildings’ façade constitutes an important consideration for the design of the building envelopes. Three semi-empirical models are available in the literature to estimate the quantity of wind-driven rain that impinges on the cladding surface, namely ASHRAE model, ISO model, and the Straube and Burnett model (thereafter called SB model). The objective of this work was to compare the consistency of hygrothermal responses and moisture performances of wood-frame wall assemblies as predicted by hygrothermal simulations with WDR calculated using these three models. These models were computed and compared for a Terrain Category III, corresponding to a suburban area as described in the ISO Standard. This comparative study was carried out for four different wood-frame wall systems differing by their claddings: fiberboard, vinyl, stucco and brick. Three building heights were considered: a 2-torey house (6 m) with pitched roof, a 4-storey (10 m) and a 12-storey (30 m) buildings with flat roof. Three Canadian cities belonging to different climate zones were selected for simulations: Ottawa (ON), Vancouver (BC) and Calgary (AB). In each city, simulations were run for two years as selected from a historical climate data set based on the moisture index (MI). The first year was the year with the median MI while the second year was the year with the highest MI. The wall orientation receiving the most winddriven rain for the second year was selected for simulations in each city. Material properties were taken from the NRC material property database. Water infiltration through the assembly was assumed to be 1% of the wind-driven rain as suggested by the ASHRAE Standard 160. Temperature and relative humidity of the outer layer of OSB sheathing were compared amongst the three WDR models. The mould growth index on the outer layer of the OSB sheathing was used to compare the moisture performance predicted using the three WDR calculation methods. |
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