Energy and comfort transformations in multiresidential buildings

Bring in the fresh air

In October 2016, the project team focused their efforts on improving the ventilation systems for the mid- and low-rise sites, which, like most other multiresidential buildings, suffer from under-ventilation in the corridors.

Pre-retrofit testing revealed the fresh air supply rates were 43 per cent below capacity across the sites. Additionally, pre-retrofit surveys revealed 49 per cent of the residents were bothered by odours from neighbouring units on a daily basis.

At the low-rise site, the fresh air supply and return duct systems were cleaned, including the fire dampers in the bathrooms. Existing rooftop units were replaced by two new units with natural gas burners and energy recovery wheels capturing heat from the exhaust. The fans were also equipped with VFDs to modulate according to the occupancy schedule (An energy recovery wheel [or thermal wheel] is a porous heat and enthalpy recovery component in a ventilation system, which is half exposed to the exhaust air stream, while the other half is exposed to the fresh, outside incoming air stream. By continually rotating, the wheel captures some of the heat and humidity from the exhausted air and transfers it back to the fresh incoming air. In the winter, this reduces the cost of heating and humidifying the air, and in summer, it contributes to preserving the coolness in the building.).

At the high-rise buildings, only the supply ducts were cleaned, as there are no central exhaust ducts (kitchen and bathroom exhaust directly to the exterior). The absence of centralized exhaust ducts also influenced the selection of the new rooftop unit, which includes VFD on the supply fan. Cleaning at both of these sites resulted in indoor air quality (IAQ) improvements, noted by building site staff and residents. With the new makeup air units, fresh air supply now meets the requirements of the American National Standards Institute/The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ANSI/ASHRAE) 62.1, Ventilation for Acceptable Indoor Air Quality.

The reported frequency of unwanted odours has since significantly decreased: there was a 31 per cent decrease in odours from neighbouring units, 28 per cent from own cooking odours, and 20 per cent from outside odours.