Hygrothermal Anaylsis of Wood-Frame Wall Assemblies in a Mixed-Humid Climate

Abstract

This study uses a one-dimensional hygrothermal model to investigate the moisture performance of 10 residential wood-frame wall assemblies in a representative mixed-humid climate location of Baltimore, Maryland (climate zone 4A). All the assemblies include oriented strandboard (OSB) sheathing and vinyl siding. The walls differ in stud cavity thickness, level of cavity insulation, presence and type of exterior insulation, and class of interior vapor retarder. The performance of the wall assemblies is compared in four respects. First, seasonal trends in moisture, humidity, and temperature conditions are investigated, and the potential for wintertime moisture accumulation in OSB sheathing from vapor diffusion is assessed. Second, the rate at which OSB sheathing is able to dry from a high initial moisture content is compared for each wall assembly at four different times of year. Both the vapor diffusion and drying performance studies include sensitivity analyses to gauge the extent to which simulation results depend on various input parameters. Third, the response of OSB moisture content to wind-driven rain intrusion is examined. Finally, the contribution of air exfiltration to wintertime moisture accumulation in OSB sheathing is evaluated.

Citation

Glass, Samuel V. 2013. Hygrothermal analysis of wood-frame wall assemblies in a mixed-humid climate. Research Paper, FPL-RP-675. Madison, WI: U.S.Department of Agriculture, Forest Service, Forest Products Laboratory, 27 p.