A Methodology to develop moisture management strategies for wood-frame walls in North America: application to stucco-clad walls

Abstract

Effective moisture control in the building envelope is essential if acceptable service life is to be achieved for the built environment. Effective moisture control implies both minimizing moisture entry into the system, and maximizing the exit of moisture, which does enter, so that no component in the system stays 'too wet' for 'too long'. But what is "too wet" and "too long"? At the institute for Research in Construction, National Research Council of Canada, a research project called MEWS 1 (Moisture Management for Exterior Wall Systems) was initiated to answer the above questions. The project has now resulted in a methodology that leads to design considerations for improved moisture management strategies for any wall assembly at any geographic region in North America. The methodology includes the integration of information from a review of field practices (Rousseau et al., 2002), extensive measurements of hygrothermal properties of building materials (Kumaran et al., 2002), definition of environmental loads (Cornick et al., 2002), investigation on damage functions (Nofal and Kumaran 1998), experiments on wind-driven rain penetration (Lacasse et al., 2001) and a detailed parametric analysis using a benchmarked and advanced hygrothermal model called hygIRC (Maref et al.2001; Mukhopadhyaya et al. 2001). This paper attempts only to summarize the methodology and lists some of the observations from its application to stucco-clad (Portland cement plaster) wood-frame walls. A full description of each module in the methodology is beyond the scope of this paper 2.