JOTS v37n2 - Impact of Climate and Geographic Location on Moisture Transport in Wood Construction Walls and Implications for Selecting Vapor Retards

This research effort studied two similarly built homes in two different geographic locations in an attempt to demonstrate the affect that climatic conditions have on the selection and installation of appropriate vapor diffusion retarders to control moisture transport in woodframed structures. Much misinformation and suppositions exist regarding which vapor diffusion retarder to use, where to place it within the structure, and whether it is even necessary. As a result, uncontrolled moisture transport is often a significant factor in the premature degradation of a structure; this also adds to poor indoor air quality resulting from the growth of mold and mildew. Nine climatic values of temperature, humidity, and air pressure were recorded at 20-30 minute intervals at various locations within the wall cavities and the outside of both test structures, for a 12-week period from January to March. These data allowed the researchers to perform calculations to predict the potential for growth of mold or mildew within the structure. Ultimately, these data were further compared for moisture transport behavior with the simulation software WUFI (“Wärme und Feuchtigkeit Instationären), a PC program developed by the Institute for Building Physics in Germany and the Oak Ridge National Laboratories in Tennessee for calculating coupled heat and moisture transfer in building components.