Methodologies for shortening test period of coupled heat-moisture transfer in building envelopes

Moisture movement and condensation through the building envelope can cause serious problems including reduction in thermal resistance of the wall, mold growth, and deterioration of the structural integrity of the wall. Full-scale tests are well suited to study these phenomena. However, a full-scale hygrothermal test requires a long testing period, typically from several months to a year, to study both wetting and drying processes. This paper presents methodologies whereby the test period is shortened to reduce cost and make large scale testing of building envelopes more affordable. A computer program for building heat-moisture simulation and test planning (BHMSTP) is developed using implicit finite-difference equations of coupled heat and moisture transfer in buildings. Two methodologies are proposed based on the analysis with the BHMSTP, shortening the test cycle from a year to a few months. In one method, indoor conditions are varied while maintaining climatic conditions constant; in the other method, weather conditions are varied, while indoor conditions are kept constant. The implementation of methodologies with the BHMSTP is demonstrated using Montreal (Canada) weather data.