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.

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Hygrothermal simulations are commonly used to evaluate the moisture damage risk of building envelopes over the long-term. For such assessment to be accurate, a proper selection of representative climate data is required. A common method is the selection of a moisture reference year from a set of available long-term climate data. For instance, the IRC-led research consortium MEWS (Moisture Management of Exterior Wall Systems) developped the Moisture Index (MI) approach, which consists of a wetting and a drying function. Therefore, the reference year selection would be based on the MI ranking. ASHRAE 160 is adopting a procedure named "the severity index" for the selection of moisture reference year. Combining climate loads and durability criteria, this method allows to select more "severe" weather years, thus providing a more representative ranking of the weather data. The objective of this paper is twofold. First, to compare the selection of the moisture reference year based on two different approaches for both historical and future climate loads. Second, the effect of chosen representative years is evaluated and compared to long-term simulation periods (of 31-years) based on the durability of building assemblies. The methodology includes hygrothermal simulations of two different types of wall assemblies located in three different Canadian cities under a changing climate. In general, higher mold index values were obtained by the long-term simulation and MRYs using Isev. Comparing the results of different models under future climates, the three methods were in good agreement, except for a brick wall facing WDR in Ottawa and Vancouver. This might be due to the Isev correlations were developed based on a north-facing stucco wall. In addition, for a north-facing wall, an extremely low mold index was predicted for Vancouver, compared to WDR direction. Thus, considering a north-facing wall as a criterion for performance evaluation might misrepresent the reality in some locations. Hence, both WDR and North orientations should be considered. A further study will be carried out to investigate the performance evaluation of Isev method for different types of wall systems and orientations.