July 23, 2013

Airtightness of new homes is critical to achieving low-energy consumption, healthy and comfortable spaces, and durability. Airtight homes require rational and predictable ventilation. A key gap and area of ongoing research is to allow credit for better performing ventilation systems, such as supply and balanced ventilation compared to exhaust, and systems with predictable filtration of outside air and recirculation filtration. This would yield energy savings and reduced moisture control risk in humid climates, without compromising indoor air quality relative to the least performing system allowed by ASHRAE Standard 62.2. Building on previous research dealing with ventilation air distribution, this study added new elements of ventilation effectiveness research, accounting for source of outside air, particle contaminants, and VOC contaminants. These new data give further support for ventilation rate credit for better performing ventilation systems. The intended result is to provide specific guidance for understanding whole-building ventilation system effectiveness, which is critical to promoting the best low energy and high value ventilation solutions.

The study focused on the in-situ impacts of various ventilation systems including the impacts of differing sources of outside air and the spatial distribution and filtration of ventilation air. The project involved testing two unoccupied, single-family, detached homes in Tyler, TX that were constructed as lab homes at the University of Texas – Tyler. The twin lab homes at UT-Tyler offered a unique opportunity for the direct comparison of nearly identical homes except for one having a vented attic and the other having an unvented attic assembly (also known as sealed cathedralized attic).


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