Effect of Temperature on Water Vapor Transmission Properties of Building Materials

Abstract

With increasing focus on energy efficient and sustainable building envelopes, the need to define the heat-air-moisture transport (hygrothermal) properties of building materials accurately cannot be overemphasized. New techniques have been evolving and being examined for this purpose. The Modified Cup Method is one such technique to determine the water vapour transmission properties of building materials. This project report describes the temperature dependency of water vapor transmission properties of four different building materials (interior finish board, engineered wood, wall sheathing membrane and roofing membrane). The tests were done following the procedure outlined in ASTM - E96 (Standard Test Methods for Water Vapor Transmission of Materials) [1]. The design and fabrication of the Modified Cup test assembly was done prior to the testing using SolidWorks software. The three different temperature levels considered were 3 ± 1°C, 22 ± 2°C and 50 ± 2°C. The results obtained from these tests were critically analysed and discussed in this report. In general, as expected, the results obtained from the tests show that the water vapor transmission rate of all four building materials considered in this study increases with temperature increment. However, the results obtained also show that water vapor permeability values do not have any consistent relationship with temperatures at which the tests were conducted.