Abstract

Abstract

Freeze-thaw degradation is one of the most prominent degradation risks of brick facades. Considering the difficulties of repairing freeze-thaw damage without replacing the materials, which may not always be an option due to heritage values, it is highly important to quantify the risk of frost damage in advance. Hygrothermal simulations have proven to be a valuable tool to assess the risk of deterioration of building facades. The performance criterion method generally applied today quantifies the number of critical freeze-thaw cycles (FTCcrit) as described by Mensinga et al (2010). This method is based on frost resistance tests that adopt high moisture contents and extremely low frost temperatures. However, building facades often experience milder frost temperatures and lower moisture contents rather than these extreme conditions. A journal article published by Feng et al. (2019) investigated the relationship of frost damage with temperature and moisture content, which enables a dose-response approach that goes beyond the existing threshold level criteria. The experimental study tested freezing temperatures from -2°C to -20°C and moisture saturation degrees from 0.1 to 1.0. This paper studies freeze-thaw risk using this advanced approach, and investigates whether the dose-response approach can lead to a clarification at what number of FTCcrit actual deterioration occurs and how this can be predicted by the use of hygrothermal simulations. Thereby, an attempt is made to derive a more representative performance criterion for frost damage.

Abstract

Due to climate change, it is expected that the amount of precipitation in most parts of Canada will increase in the coming decades. Consequently, the building envelope exposed to such climate could experience a higher moisture load than in the past, which could have a negative impact on its performance in the long run. The stucco-clad wall assembly, which has been widely employed in the construction of low-rise residential buildings throughout Canada may not be adequately designed to be resilient to the future climate. Thus, in the study described in this paper, the future moisture performance of the stucco-clad wall assembly located in two Canadian cities with different levels of moisture load, i.e., Vancouver and Calgary, subjected to projected future climate is investigated. The analysis includes two phases: conducting watertightness for a full-scale stucco wall specimen to determine the relationship between the climate data and the moisture load in the wall assembly and implementing hygrothermal simulations using the relationship obtained from the watertightness test for the performance assessment. Mould growth index at the exterior surface of the oriented strand board of stucco-clad wall assembly for the historical and projected future time periods is compared and discussed.