Estimating Foundation Water Vapor Release Using a Simple Moisture Balance and AIM-2: Case Study of a Contemporary Wood-Frame House

Proper management ofindoor humidity in buildings is an essential aspect ofdurability. Following dissipation ofmoisture from construction materials, humidity levels during normal operation aregenerally assumed to primarily depend on the building volume, the number of building occupants and their behavior, the air exchange rate, and the water vapor content ofoutdoor air A potentially large additionalsource ofindoor humidity that often is not considered is the building foundation, which is in contact with earth that commonly damp. Recent work has suggested that the rate of water vapor release from foundations may vary with season, withfoundation temperature, and with indoor humidity. This workpresents resultsfrom a casestudy of a house with a wood foundation system in which we estimatefoundation mois­ ture release given basic interior and exterior conditions, such as relative humidity, temperature, and wind speed. The Alberta air infiltration model was calibratedusing tracergas measurements in the house and usedto model air exchange. We use a simpli­ fied moisture balance model to estimate the hourly rate of foundation moisture releasefrom the basement. This rate ispresented and shown to correlate with stack-driven air exchange for this wood foundation system.