Validation of Three Methods of Selecting Moisture Reference Years for Hygrothermal Simulations

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.

Effects of air change rate and moisture load related to moisture index and the expected moisture performance of a wall assembly

“…Aggarwal et al [12] investigated the selection of Moisture Reference Years MRY, which could provide equivalent results as those obtained from a long-term climate series, using three methods: the moisture index; severity index; and, climatic index. The analysis was performed for a brick cladding wood frame wall assembly located in 3 Canadian cities, which each city having a different level of moisture load, the brick-clad wall assembly was subjected through simulations to historical climate from 1986-2016, and future projected climate from 2062-2092 generated from a climate model.…”

Accuracy of using Moisture Reference Years for assessing the Long-Term Moisture Performance of Wall Assemblies

“…The first step is to rank the years of a longterm series in terms of their moisture severity using either climate-based indices or performance-based indices, e.g., the Moisture Index (MI)4, Severity Index (Isev) [5], Climatic Index (CI) [6], or Mould Growth Index (MGI) [1]. Thereafter, the MRY is selected as the worst year [7,8] or a combination of years having different moisture severities [9,10]. Chetan et al [8] investigated the accuracy of using three methods to sort years in a given climate series for a brick-clad wall assembly in terms of their moisture severity for the purpose of selecting MRYs: MI, Isev, and CI.…”

“…Thereafter, the MRY is selected as the worst year [7,8] or a combination of years having different moisture severities [9,10]. Chetan et al [8] investigated the accuracy of using three methods to sort years in a given climate series for a brick-clad wall assembly in terms of their moisture severity for the purpose of selecting MRYs: MI, Isev, and CI. The cumulative number of hours when mould growth is greater than 3 for the MRY selected, i.e., the year having the 97th percentile value of the index, was compared to that obtained from all the individual years of the longterm series.…”

Prediction and Ranking of Moisture Severity of Climate Years Using Supervised Projection to Latent Structures Applied to Tall Wood Buildings

“…The applicability and limits of existing methods have been addressed elsewhere (Cornick and Dalgliesh 2003, Aggarwal et al 2020, Salonvaara et al 2011, Singh 2017, Vandemeulebroucke et al 2021, 2023. The response-based methods seem to be more reliable (Aggarwal et al 2000, Vandemeulebroucke et al 2021, 2023.…”