Reliability assessment of design reference year for evaluating the impact of climate change on moisture performance of wood frame walls

The changing climate may influence building performance in several different aspects. In respect to the hygrothermal performance, excessive moisture arising from climate loads and present in wall assemblies over a prolonged period of time is the cause of many detrimental effects on wall components; notably, such effects may become more significant under a changing climate. The occurrence of these effects can be assessed by undertaking hygrothermal simulations. However, numerical simulations can be time-consuming, especially when evaluating the detrimental effects over a long period, which is necessary for assessing the impacts of climate change on building envelope components. A means to reduce such a time consuming and costly simulation effort is to select a set of representative years from the series of long-term climate data; a set of Moisture Reference Year (MRY), with the expectation of obtaining similar results as those obtained from the long-term simulations. This study assesses the reliability of using MRY for evaluating the long-term hygrothermal performance of wall assemblies. The MRY were selected based on moisture index (MI) rankings for historical and future climatological periods. The simulations using MRY were repeated at least 2 times and up to 10 times, with the results compared to those obtained from 31 years of consecutive simulations. Two types of wood-frame wall assemblies, each with different types of exterior cladding, were analyzed. Several criteria were selected for comparison. The results showed that the required number of repetitions of MRY is determined by the parameters used for comparisons.