Stochastic modelling of hygrothermal performance of highly insulated wood framed walls

Abstract

Recent years, the majority of building codes in North America require an energy efficient envelope to improve the building energy efficiency. There are different design strategies to achieve a higher insulation level of the wood framed building envelope, such as increasing the depth of stud cavity to accommodate thicker insulation or adding an exterior insulation while keeping the depth of stud cavity unchanged. However, the highly insulated walls may lead to a higher risk of moisture problems. The deep cavity walls will reduce the temperature of the wood sheathing, which may increase the potential for condensation and mold growth. The exterior insulated walls may result in a low drying capacity of the wood sheathing if the exterior insulation has a low vapour permeance. Although hygrothermal simulations have been widely used to investigate the moisture performance of wood framed walls, the uncertainty of the input parameters may lead to discrepancies between simulation results and real performance of the walls. This paper investigates the hygrothermal performance of highly insulated wood framed walls-deep cavity wall and exterior insulated wall using a stochastic simulation approach. The uncertainties of the input parameters including the material properties, air leakage and rain leakage rates are taken into account in stochastic modelling. The mold growth risks of the walls are evaluated based on the stochastic simulation results.

Hygrothermal response of a wood-frame thick-wall assembly to rainwater wetting under future climate scenarios in Canada

“…Based on the results of the sensitivity analysis performed, the basecase WIRL wall assembly is found to demonstrate the greatest risk for failure when a rainwater leak is present, with the predicted moisture content of the exterior sheathing exceeding and remaining above the safe limit in both the 0.5% and 1% leakage scenarios. These findings are in keeping with the results presented by Sehizadeh and Ge (2016) and Wang and Ge (2018), who demonstrate a greater increase in the predicted moisture content of a thick-wall assembly under a 1% rainwater wetting scenario compared to air-leakage only scenarios. To investigate the impact of a future climate on the performance of the assembly with a global temperature rise of 3.5°C, the assembly with 1% rainwater leakage is used.…”

Effect of rain leakage on hygrothermal performance of highly insulated wood-framed walls: a stochastic approach

“…The stochastic modelling approach developed by Wang and Ge (2018) is applied to investigate the impact of rain infiltration on highly insulated wood-frame walls. This section presents the specific methods of this approach, including hygrothermal base models' setup and stochastic models' setup.…”

In-Situ and Predicted Performance of a Certified Industrial Passive House Building under Future Climate Scenarios

“…Although data transmission and sensor failures occurred, the installation of multiple sensors within both the north and south wall assemblies allowed for sufficient data collection and analysis of the hygrothermal behavior of the assemblies based on the data collected from the remaining sensors. A low level of uncertainty is attributed to the data collected from the north wall sensors that were used for the predicted performance under future climate scenarios as the data show trends consistent with those of thick-wall assemblies in cold climates [23] and the predicted hygrothermal behavior using the WUFI ® Plus software. The data collected from the remaining six sensor arrangements showed that at no point during the data collection period of 18 July 2018, to 4 March 2020 was 100 percent relative humidity achieved in either the north or south wall assemblies.…”