| Résumé | Water penetration in the wall assembly through deficiencies, resulting from the coupled action of rain and wind, also known as wind-driven rain (WDR), can cause degradation of tall wood building components (e.g. mould growth, wood decay), thereby by reducing their performance and service life. Three semi-empirical models are available in the literature to estimate the quantity of wind-driven rain that impinges on the cladding surface: the ASHRAE model, the ISO model, and the Straube and Burnett model (SB model). The objective of this work was to compare the consistency of the hygrothermal responses and the moisture performance of the CLT panel used in massive timber walls as predicted by hygrothermal simulations with WDR calculated using the three models. Three Canadian cities having contrasting climates were selected for simulation: Vancouver (BC) located in Climate Zone 5 with a minimum RSI-value requirement of 3.60; Ottawa (ON) located in Climate Zone 6 with a minimum RSI-value requirement of 4.053; and Calgary (AB) located in Climate Zone 7A with a minimum RSI-value requirement of 4.76. Three massive timber wall systems that differ by their insulation type and thickness were considered: a wall having 2 layers of 89 mm mineral fibre insulation with RSIvalue of 5.7 (W1); a wall having two layers of 64 mm mineral fibre insulation with RSI-value of 4.4 (W2); and a wall having a sprayed polyurethane foam insulation of 89 mm with RSI-value of 4.5 (W3). As well three building heights (10, 30 and 50 m) were tested. Due to RSI-value restriction, only wall W1 was considered in Calgary. For Ottawa and Vancouver, all the three walls were considered as they all meet the minimum R-value requirements. In each city, simulations were run using DELPHIN v5.9.4 for two years as selected from a historical climate data set based on the moisture index. For this study, only the fibreboard cladding was considered. The wall orientation receiving the most WDR over the two-year period was selected for simulations in each city, assuming that the building is located in city centre. Material properties were taken from the NRC material property database. Water penetration in the structure was assumed to be 1% of the wind-driven rain as recommended by the ASHRAE Standard 160. Temperature and relative humidity of the outer layer of the CLT panel were compared amongst the three WDR calculation models. The mould growth index on the outer layer of the CLT panel was used to compare the moisture performance predicted using respective models. |
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