The Northwest Energy Efficiency Alliance (NEEA) contracted with Ecotope, Inc. to examine the effects of increased envelope airtightness (a measure of air infiltration through building components such as walls, windows, doors, ceilings, and floors) on the performance of multifamily buildings. Driven by recent Energy Code changes in Washington State, this study seeks to determine the impact of the airtightness target, 0.4 CFM/ft2, on ventilation system and exhaust appliance performance. The study evaluated twelve buildings, both mid-rise and high-rise. Of the twelve, nine were designed around exhaust-based ventilation systems and the remaining three had balanced-flow ventilation systems with energy recovery ventilation (ERV).
The study shows that the tightness target, in combination with an exhaust-only ventilation system, is enough to achieve full-building depressurization in mid-rise multifamily buildings and is an achievable target with no demonstrable adverse effects on building occupants. In comparison, increasing airtightness beyond this level (to 0.25 CFM/ft2 or tighter) without changing the ventilation system does not save energy, may introduce comfort and noise complaints, and may begin to impact the performance of appliances such as dryers.
Find the Phase III Report here.