Indoor humidity is a very important factor influencing indoor air quality, thermal comfort, energy consumption, and building envelope performance. Moisture buffering effect is considered as an efficient factor in moderating the indoor humidity level.

In this study a full-scale two-storey wood-framed test-hut is built inside an environmental chamber to investigate the moisture buffering effect. The parameters studied include two different interior surfacing materials (gypsum board and wooden panels), different ventilation rates (0.3, 0.5, 0.75 and 1.0 ACH), and moisture generation rates of 2.3, 4.6, and 9.2 g/m³·hr (1.05, 2.01, and 4.02 grain/ft³.hr). A new methodology is used to evaluate moisture buffering based on the calculation of the amount of moisture absorbed/released by the surface materials.

This paper presents the experimental design and the preliminary results for uncoated gypsum board at 0.5 ACH with moisture generation rate of 4.6 g/m³·h (2.01 grain/ft³.hr). The results show that gypsum can absorb as much as 9.9 g/m² (14.19grain/ft²) moisture in one day cycle; additionally, the relative humidity across the room shows differences of up to 15% RH among different locations.

Presented at Thermal Performance of Exterior Envelopes of Whole Buildings X – December 2007

Units: Dual