Abstract

The objective of this thesis aimed (1) to evaluate the effectiveness of the existing test methods used in characterizing moisture performance of weather resistive barrier (WRB) products, and (2) to provide a benchmark for assessment of different boundary conditions. The test materials were placed between a layer of water and various types of hygroscopic sinks including vacuum cast gypsum, oriented strand board (OSB), thick adsorbing paper (blotter) and a desiccant (anhydrous calcium chloride). The WRB were either placed directly in contact with the hygroscopic sink or were separated from it by an air gap. These tests indicated that moisture transport was highly dependent on the conditions introduced on the upper and the lower surfaces of the WRB. This thesis reports the results of a series of experimental studies, which examined moisture transport to characterize WRB for input into material standards. The new test methods developed in the thesis include: modified inverted cup ( MIC ) test for measuring the maximum possible total moisture transmission, moisture flux ( MF ) test for measuring moisture flow to an OSB or plywood substrate, and liquid penetration resistance ( LPR ) test for measuring onset and the rate of the liquid phase transport. The test methods were used to examine moisture transport through new WRB. The test were also used to evaluate effect of penetrations, outdoor weathering, and contribution of detergent dissolved in the interstitial water. Subsequent to the material testing, an assembly testing provided a comparative evaluation of such effects as penetrations or additives in a stucco layer. Proposed in this thesis are new laboratory test methods and the acceptance criteria to be incorporated in the next edition of North American material standards. (Abstract shortened by UMI.)