Hygrothermal characterization and performance of wood in assemblies accounting for contamination by <i>Serpula lacrymans</i>

Some wood-destroying fungi are increasingly present in Québec, Canada, and this reported increase seems to coincide with climate change. Serpula lacrymans is a brown rot fungus that is one of the most destructive fungi reported across the province. This paper documents and simulates the spread of biodegradation in wood-framed buildings and, more specifically, investigates this spread considering the impact of S. lacrymans contamination of wood components on the hygrothermal performance of wall assemblies. The work presented is two-pronged. First, we assess physical and mechanical properties of pine and spruce wood degraded by S. lacrymans . Density, porosity, water vapor permeability, water vapor sorption, capillary water absorption, water content at capillary saturation and effective saturation have been measured to provide comparative insight for healthy and contaminated wood. Degraded samples showed an increase in their water vapor resistance factor and water content at capillary saturation as well as a general decrease in values of sorption isotherms and capillary water absorption coefficients. Effective saturation values were higher for degraded spruce samples and lower for degraded pine samples. The mechanical properties tested showed that, even if the measured mass loss is negligible, loss of mechanical strength can be considerable. Second, we assess how the presence of damaged wood affects the hygrothermal performance of different envelope assemblies for seven climatic sub-regions in Québec. The degradation criterion is based on the duration of exposure to humidity and temperature levels conducive to the fungal growth. S. lacrymans has a particular ability compared to other decay fungi in that it can move water source toward sought nutrients. Hence, fungal presence and distribution in the envelope assemblies is modeled with two means: modified water transport properties obtained from laboratory measurements on contaminated wood and addition of water flux in wood components to simulate hyphae-borne moisture transfer in the assemblies.