Volume 33, Issue 5 (September 2005)
Use of the Modified Cup Method to Determine Temperature Dependency of Water Vapor Transmission Properties of Building Materials
This paper describes a modified cup method and its application to investigate the effects of temperature on the water vapor transmission (WVT) properties of building materials. The modified cup method is a simple and versatile technique that allows the user to vary the temperature condition of the test without altering the relative humidity. Two commonly used building materials considered in this study were fiberboard and gypsum board. The five temperature levels under consideration were between 7°C and 43°C. The WVT properties were measured at 50 % average relative humidity. The results obtained from these tests are critically analyzed and reported in this paper. These results demonstrate that there is a steady exponential increase of WVT rate, through both the materials tested, with temperature. However, water vapor permeability (WVP) through the materials shows no significant change due to the variation of temperature between 7 and 43°C. The general observations made in this study confirm that the modified cup method could be used reliably to measure WVT properties of building materials. Detailed analysis of the test results also reaffirms the fact that, for fiberboard and gypsum board, at 50 % average relative humidity condition, the WVP is not dependent on the temperature condition.