A number of hygrothermal numerical simulation packages are available, either wholly or partially dedicated to heat, air and moisture transfer simulations of building materials and wall assemblies. The objective of this work was to compare the hygrothermal responses and the moisture performance of western red cedar and composite wood claddings of a wood frame wall as predicted by four hygrothermal simulation tools: DELPHIN, WUFI, hygIRC, and Comsol. Three Canadian cities having different climates were selected for simulation: 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. The wall orientation receiving the most wind-driven rain for the two years were selected for simulations. Material properties were taken from the NRC material property database. Cladding temperature and relative humidity values as well as the moisture accumulated in the entire structure were compared amongst the results obtained from the four tools. Mould growth index on the cladding surface was used as a basis for comparing the moisture performance predicted by the tools. Temperature profiles on the cladding surfaces in the three cities considered were all in good agreement for the four tools. For composite wood cladding, all four models gave similar trends for relative humidity and for each of the three cities. However, WUFI tends to predict higher relative humidity as compared to results obtained using either DELPHIN, Comsol or hygIRC. For red cedar cladding, hygIRC predicts higher relative humidity than that predicted by other tools in Ottawa and Vancouver. Simulation results obtained with constant wood properties suggest that amongst other factors, material property processing may explain these discrepancies. Results for total accumulated moisture in the structure showed that WUFI tends to accumulate more moisture in the structure than other tools, which is probably related to how WUFI computes the absorbed wind-driven rain at the cladding surface. The predicted values of the mould growth index over the two-year period by the four tools were all below the threshold of 3 (no visible mould growth), but in general, WUFI provides more conservative predictions, offering higher values for mould risk as compared to the other tools.

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