| Abstract | Advanced hygrothermal models can predict temperature and moisture conditions in wall components subjected to actual weather conditions, but damage functions are required to predict consequences for building performance. This paper documents progress towards criteria for unacceptable damage and discusses the work underway to define damage functions. Durability is addressed in Canadian building codes where it impacts safety or health. It, therefore, proposed that damage to building envelopes be considered in two ways. First, strength loss to the system, which determine its level of safety; second, effect on the health of the occupants from unacceptable levels of fungal spores or metabolites entering the living space. Damage functions for strength loss require an improved understanding of the limiting conditions of humidity and temperature for decay and of load distribution in platform-frame construction weakened by decay. Work is underway or planned in each of these areas and some preliminary results on time to establishment of decay in OSB will be presented. Damage functions for health impacts are very complicated to derive because it requires the knowledge of many interacting aspects. These aspects include knowledge of conditions affecting the type and amount of mould in the wall, air leakage or diffusion into the living space, exposure levels from exterior air, other building systems, health risk factors, and threshold levels for spores and metabolites to be determined by medical authorities. These threshold levels are also very difficult to establish because they vary from age group to another end even among individuals. |
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