Ventilation with outdoor air has been the accepted method for controlling moisture and overheating in residential attics. This is recognized in the Building Code which requires that the total vent area must be l/300th of the attic floor area. However, how much ventilation is provided and how this ventilation affects moisture accumulation in an attic are not well understood. The present study attempts to provide some answers to these questions. The study consists of two parts. First, detailed measurements were carried out in two separate attics located at a field test site.
Preliminary work has indicated that thermography can be used to determine air leakage pathways from or to buildings. Accurate measurements have now been taken using temperature controllable environmental chambers.These results reinforce the potential useof thermography for this application. In conjunction with the physical measurements a simulation has been carried out using computational fluid dynamics.
The equivalent leakage area algorithm is used to illustrate the use of statistical simulations to predict distributions of infiltration and energy loss for buildings. The important parameters in the model are: leakage at 50 Pa pressurisation, indoor and outdoor temperature, leakage in the ceiling and the floor, wind speed, building height and shielding class. Most of these parameters are not known accurately. In the statistical method we assumed for each a distribution based on measurement or good guess.
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