b'The mechanical system includes a Passive House-certified energy recovery ventilator with variable sensible heatUse An RCABC Memberrecovery efficiency between 86.4 per cent (at 25 C) and 86.5 per cent Its Chaos Without Us(at -7 C). The system delivers ventila-tion air to the heat pump fan coils on each floor to ensure circulation throughout the structure.Heating and cooling is provided by two electric variable refrigerant flow heat pumps that allow simultaneous heating and cooling in different zones in the building. Domestic hot water is provided by a roof-mounted, low-temperature heat pump water heater, with a reverse cascading storage tank system that incorporates electric resis-tance maintenance and backup heating. The heat pump COP varies from1.9 at -9 C to 4.2 at 24 C.PROJECT CHALLENGESMeeting the Passive House standard for the project involved a number of chal-lenges in the construction design. These included reducing the window-to-wall ratio, window positions, air tight-ness, protecting the integrity of the air barrier and mitigating or eliminating heat loss from thermal bridges.Windows are the lowest thermal performing component in the build-ings wall system, states Cody Belton, Passive House Specialist with Morrison Hershfield, the projects Passive House consultant. An early-stage study of window-to-wall ratios by IBI Group changed the window layout, elimi-nating narrow windows to decrease604-882-9734rcabc.org transmission at exterior window-to-wall transitions, which were the mostFind the complete Roofing Practices Manual at: RoofStar.caimpactful thermal bridges. Mitigating heat loss at these locations wasSPRING/SUMMER 2022 15'