A new test method to determine the relative drying capacity of building envelope panels of various configurations

Abstract

In the context of a collaborative research project with industry and government, a two-story test hut, consisting of thirty-one 2438 mm (8 ft) high and 762 mm ( 2 1 2 ft ) wide wall assemblies and installed with 25 gravimetric samples in each assembly to monitor the moisture content change, was designed and erected within a large-scale test chamber to investigate the drying capacity of different envelope configurations. The test was performed under steady-state climatic loadings representing wet seasons. Uniform moisture loading was achieved by the use of water trays on load cells placed on the bottom plate within the stud cavities of the wall assemblies. This method submits the different wall configurations to wetting by evaporation and drying by evacuating moisture out of the stud cavity. In search for an indicator or yardstick of the relative drying capacity of different wall configurations, a new calculation method by mapping was developed. The method estimates the amounts of moisture absorbed by components surrounding the stud cavity. The moisture transported out of the cavity is the difference between the total water evaporated from the tray and the water absorbed by the wall components. The ratio between the water evaporated and the vapor evacuated is an indicator of the drying capacity of a given wall configuration in relation to others subjected to a predetermined set of conditions.