Wall Moisture Problems in Seattle

In the past few years, major moisture-related problems have appeared in the northwestern U.S. and southwestern Canada. These problems have been catastrophic, amounting to billions of dollars in premature damage. Several forensic studies have been performed that attribute the problem to more than poor workmanship, as meticulous attention to details still has not completely resolved the reoccurrence of the moisture-related problems. Moisture transport through a building envelope influences not only the durability, indoor air quality, health, and safety of the inhabitants but also the energy efficiency of the envelope system. The influences of moisture transport are experienced differently in lightweight (hygroscopic) or heavyweight (moisture massive) building envelope systems. In almost all cases of moisture-related damage, the building envelopes were not designed to handle the moisture loads that were present due to the imposing environment. The moisture damage that has appeared clearly indicates the need for proper moisture control analysis of building systems. Solutions to moisture-induced problems may be difficult to achieve when several interacting mechanisms of moisture transport are present. Research is continuously upgrading existing knowledge of these complicated issues. In this paper, the authors will provide a scope of the overall problem in Seattle, Wash., and the research activities currently underway. The paper will focus on the research approach undertaken in terms of “moisture engineering.” Preliminary results will be provided to show the effect of stucco materials and interior vapor control strategies on the hygrothermal performance of a representative stucco-clad wall system.