Abstract

With the increasing levels of insulation employed for energy saving purposes, building envelopes require a reliable hygrothermal analysis to avoid mould and other moisture-related problems. Air leakage has long been identified as one of the primary drivers of moisture transport through building envelopes. Wind is always mentioned as one of the three driving forces of air leakage, but seldom is wind explicitly considered for hygrothermal analysis. In other words, under current practice, hygrothermal analysis will yield exactly the same result regardless of whether the building is in a windy or a windless area.

This study focused on identifying the wind speed and wall orientation that would increase the risk of developing mould in the wall assemblies for a low-rise building. Wind pressure coefficients were used to calculate wind-induced pressure differentials acting across the walls which were then integrated into the Air Infiltration Model. Design variables were structured into a parametric study. The wall performance was evaluated in a heat, air, and moisture (HAM) simulation program.

Through a parametric study this thesis has qualitatively illustrated that wind-induced exfiltration can have a significant effect on the hygrothermal performance of walls of low-rise buildings, and that under some conditions, if wind is ignored mould risk can be underestimated. Based on the limited work of this study, wind speeds under which mould is more likely to be underestimated
were quantified, the corresponding wind speed values are not meant to be definitive but rather a demonstration that a similar guideline is worthwhile to be developed.