Experimental evaluation of potential transport of mold spores from moldy studs in full-size wall assemblies

A research project was undertaken on full-scale wood-framed wall assemblies to evaluate the transport of mold spores from slightly moldy wood studs within the stud cavity to the indoor environment. A series of tests were performed with variations of such parameters as rates and patterns of air leakage, presence or absence of insulation and vapor barrier. Wood studs with slightly visible surface molds (10% of surface area) were used for some of the wall assemblies, while clear studs were used for the remainder. A pressurization setup was used to create an air infiltration through the wall assemblies. Air samples were taken to measure the spore concentrations in the stud cavities, infiltrating air, and laboratory background. Statistical significance testing methods were used to draw observations and conclusions from these data. The results from this experiment do not support a statistically significant increase of spore movement out of stud cavities into the indoor space due to the use of slightly moldy studs in the wall assemblies.