Study of gypsum board material properties required to maintain high indoor relative humidity in buildings in cold climates

Abstract

Studies have shown that building relative humidity (RH) in the range of 40% to 60% has positive effects on health, including limiting growth and transmission for both bacteria and viruses. These levels are easily obtained in moderate to warm climates but are difficult to maintain in cold climates. There lies a need to research possible advancements in building material properties that can maintain RH within the desired range, higher than what is generally accepted in buildings in cold climates.

This report covers the study of gypsum board and the alteration of its material properties in order to achieve the desired range for indoor RH. A 1-dimensional moisture simulation tool, WUFI Pro, is used to analyze a building wall construction with a variety of user-defined gypsum board materials for two cold climate locations: Vancouver, BC and Winnipeg, MB. Material properties that are altered include porosity, specific heat capacity, and the moisture storage function. The simulation results show that changes in porosity and specific heat capacity have insignificant effect on the indoor RH, whereas changes to the moisture storage function do.

For Winnipeg, a test material with an increased water content per RH of 20% resulted in an indoor RH minimum and maximum of 45.8% and 72.9%, respectively, compared to 36.3% and 81.5% for the base case.