Abstract

Hygrothermal simulations are necessary to permit analyzing moisture performance when designing building envelopes. Owing to the high computing time and cost of the long term simulations, a common approach is to select representative year(s), the Moisture Reference Year(s), from a longterm series of climate data. It is assumed that the use of Moisture Reference Year(s) (MRYs) provides equivalent results as those provided using long-term series. The selection of MRY(s) is by itself based on the one of the methods available in the literature. In the present study, three methods of selecting the MRYs were evaluated i.e. the moisture index (MI), severity index (Isev) and climatic index (CI). Simulations were performed using individual years of historical climate data extending from 1986 to 2016 and projected future climate data representing the scenario with a 3.5°C increase in average temperature which is expected to occur from 2062 to 2092. Brick cladding installed on a wood frame wall assembly subjected to the climate of three different Canadian cities was selected for analysis. The cities selected were Vancouver (BC), Calgary (AB) and Ottawa (ON). These cities have differing levels of moisture loads. The year having the mould index value more than 3 for highest number of hours among the individual years was compared with the MRY given by three selected methods. A method was considered to be accurate in terms of the prediction if the year selected by that method gives the number of hours with mould index more than 3 which lies in the same class as that of year having maximum corresponding value. In general, it was observed that none of the methods provides the worst year with 100% accuracy, however for most of the cases, Isev method performs better than other two methods in terms of MRY selection.

Abstract

Due to climate change, higher temperatures and rainfalls are expected to happen in some areas of Canada, which might increase the climate loads on buildings and lead to premature degradation of moisture-sensitive materials in wall assemblies. To investigate potential durability issues in three cities across Canada (Ottawa, Vancouver and Calgary), code-compliant wood-frame walls with two types of claddings, stucco and brick, were simulated using Delphin 5.9. Two different climate data sets, historical and future when a global warming of 3.5ºC is expected to be reached were used. The hygrothermal performance in terms of mold growth risk was analysed with respect to cladding types, considering air leakage. All the three cities are similarly warmer in the future. However, wind-driven rain (WDR) is higher in Vancouver than in Ottawa and Calgary. With brick cladding the relative humidity is kept below the threshold for mould development only in Ottawa and Calgary. With stucco in future, while Ottawa shows greater mould indices than historical, Calgary shows opposite behavior. The results suggest that the risk of mould growth due to air leakage may decrease in the future.