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ABSTRACT HEADING

Internal moisture generation, or moisture generated by building occupants via activities such as respiration, cooking, bathing, and cleaning, is a critical contributor to the overall moisture load in a home. Other contributors to total moisture load include natural and mechanical ventilation, mechanical humidification/dehumidification, vapor diffusion, and sorption. Total moisture load is a critical input required for design and analysis of building enclosure and HVAC systems yet data quantifying internal moisture generation is scarce, and data that do exist show varied results. This discrepancy is largely due to the difficulty with making either direct or indirect measurements of the moisture source(s) in occupied homes. Additional data quantifying internal moisture generation rates in newer housing is useful in determining the continued relevance of current design guidance.

ASHRAE RP-1844, sponsored by TC 1.12 Moisture Management in Buildings, is using a moisture balance approach to estimate internal moisture generation rates in occupied homes in the southeastern US. This paper describes the moisture balance model, results from applying the model to data collected in 12 homes, and ongoing efforts to validate the model in simulated occupancy laboratories. Occupied home data were collected in partnership with the US Department of Energy Building America program, which is using the data to investigate whole house mechanical ventilation as a control measure for indoor air quality.