A field investigation of wood-framed wall assemblies was conducted to monitor the moisture performance of various exterior wall constructions with intentional air leakage and seasonal moisture injections between the cladding and sheathing over a 20-month period from November 2013 to June 2015. The research focused on four specific studies: moisture performance of Extended Plate and Beam (EP&B) walls, walls with air leakage versus air sealing, 2x4 walls with various types of exterior insulation, and baseline walls insulated with kraft-faced batts and unfaced batts. This report covers the field monitoring results and compares the performance of the 10 wall pairs.
The field study was conducted in a mixed-humid climate located in Upper Marlboro, Md., on the campus of Home Innovation Research Labs, located 20 miles east of Washington, D.C. Wall sections with each of the cladding systems were investigated in North and South orientations. Over the test period, indoor humidity conditions were controlled to 30 to 60 percent RH during the winter heating period. Stud bay temperature and humidity conditions were monitored, as was moisture content in the exterior sheathings and studs. During this winter portion of the testing, the wood-based components of the wall sections indicated moisture levels significantly higher for the stucco, stone, brick, and fiber cement walls relative to the walls with vinyl siding with or without exterior insulations. The winter peak moisture content in the sheathing for these walls ranged from 20 to 24 percent; higher than the generally accepted 20 percent Moisture Content (MC) level for wood products (Drumheller and Carll, 2010). Thus, they might have been at risk for moisture problems such as rot and mold growth.