Addressing overventilation through fan speed reduction in multi-unit residential buildings with pressurized corridor and in-unit ventilation systems

• Pressurized corridor fan speed reductions tested to reduce ventilation energy use • Central ventilation could not maintain positive corridor pressure on lower floors • Range hoods and dryers raised corridor-to-unit dPs by 23±4Pa and 9±4Pa • Fan speed changes did not affect residents’ perceptions of indoor air quality • Reducing the fan speed to 50% saved 5.5 kWh/m²/year in the test building In-unit ventilation systems (e.g. ERV/HRVs) are becoming increasingly popular in new multi-unit residential buildings (MURBs) in Canada, however centralized ventilation systems are still needed to supply air to the corridors. Corridor ventilation is typically delivered with a pressurized corridor (PC) system, often designed using industry rules of thumb (e.g. 30 cfm /door), resulting in excessively high supply flow rates that could meet the combined corridor and unit ventilation demand. This is an industry holdover from when PC systems were responsible for the whole building ventilation load, and these higher-than-necessary flow rates result in energy waste. A field study was conducted in a MURB located in Toronto, Canada, to determine if PC supply flow rates could be reduced to save energy, while still maintaining corridor pressurization and occupant satisfaction. The study also analysed the impact of occupant behaviors and weatherstripping additions on corridor air pressure changes. During the winter, when stack effect was most severe, the PC system could not maintain positive pressurization on the lowest floors, even at the highest fan speeds. Despite pressurization issues, minimum corridor flow rates required by ASHRAE 62.1 were consistently met and surveys show residents did not perceive changes in air quality as supply flow rates were decreased. Meanwhile, lowering the fan speed to 50% capacity could save 5.5 kWh/m²/year, demonstrating that reducing corridor air supply can be a practical energy saving strategy despite some loss of pressurization on the lowest floors.