Mapping of Air Leakage in Exterior Wall Assemblies

Abstract

A full-scale wood frame test hut with nine wall specimens, typical of low-rise residential construction in the province of Quebec, was built inside an environmental chamber. This test hut was subjected to 66 days of simulated winter and 47 days of late spring climatic conditions to verify the feasibility of different methods of mapping and representing graphically air exfiltration. Through a better understanding of the movement of air through the envelope, the risks related to moisture condensation within the envelope for different wall compositions can be better ascertained. The air leakage pattern characterization methods implemented were two-dimensional grid moisture content monitoring and three-dimensional grid temperature monitoring. The moisture content and temperature data were presented in a graphic form, using isohygrons and isotherms. Temperatures without the impact of air leakage were also calculated using a three-dimensional conductive heat transfer model. The air leakage pattern characterization methods and the resulting moisture and temperature maps are presented and discussed herein.

A 2D model for coupled heat, air, and moisture transfer through porous media in contact with air channels

“…Over the past twenty years, experimental work and on site observations brought to light the major inuence of air ow on the hygrothermal eld [5,6]. Modelling research work rstly focused on coupling heat and air transfers in building components.…”

In-cavity evaporation allowance—A drying capacity indicator for wood-frame wall system

“…The diffusion and convection loads can be setup directly in experiments by providing appropriate temperature, relative humidity, and air pressure on both sides of the wall panels under testing. For example, TenWolde et al [13], Salonvaara et al [9] and Hansen et al [14] introduced moisture through vapor diffusion only; while air leakage carrying moisture (convection) provided a more severe load in Desmarais et al [15].…”

Risk Assessment of Energy-Efficient Walls

“…The main reason behind this knowledge gap is that simulation tools that attempt to evaluate the effect of airflow (e.g., WUFI  1D, WUFI  2D and Transient-Coupled-Conduction and Convection in 2D) have not been calibrated and/or validated. Moreover, although Desmarais et al (2000), Langmans et al (2012) and Fox (2014) have gathered laboratory or field data, none of them have used it to validate simulation tools that predict hygrothermal performance. This is particularly problematic because the quantitative assessment performed as the next step in this protocol relies on the effective simulation and characterization of the impact of the influential parameters on the moisture content of the wall assembly.…”

“…A limited number of studies have aimed for a somewhat similar objective. However, these studies represent partial hygrothermal evaluations because they mostly relied on field tests (Fox 2014, Home Innovation Research Labs 2014, laboratory studies (Desmarais et al 2000, Langmans et al 2012, or simulations (Ojanen et al 1994, Straube and Smegal 2012, Glass 2013, Lepage et al 2013. In these evaluations, field and lab tests were limited to very specific scenarios, while results from simulations were not verified with empirical data.…”

“…In these evaluations, field and lab tests were limited to very specific scenarios, while results from simulations were not verified with empirical data. Moreover, moisture accumulation due to airflow was minimally accounted for even though researchers have raised concerns about the effects of airflow on the durability of building envelope assemblies (Ojanen et al 1994, Desmarais et al 2000, Künzel et al 2011).…”