Energy performance, comfort, and lessons learned from an institutional building designed for net zero energy

This paper examines the early performance ofthe Varennes Library, a building designed for net-zero annual energy balance in Varennes, near Montreal, Canada. It produces electricity from a 110.5 kWp building-integrated photovoltaic (BIPV) system where heat is also recovered from a section of the array and used to preheat the outdoor air intake. The building's many architectural and mechanicalfeatures were integrally designed to achieve the net zero energy target over a five-year averaging period with several key decisions made at the early design stage. These include the shape, area, and orientation ofthe roofthat maximizes electricity productionfrom the BIPV (part BIPV/T [building-integrated photovoltaic/thermal with heat recovery]) system and a design layout that promotes daylight penetration and natural ventilation/free coolingduring the cooling season. In thefirstyear after inauguration, an operational energy use intensity (EUI) of 24.8 kBtu/tfy (78.1 kWh/m²y) was achieved and has since been reduced to 22.20 kBtu/fy (70.0 kWh/m²y). Considering renew-ables production, the net-energy use intensity (EUI) is 4.60 kB tu/ fi²y (14.5 kWh/m²y). This is a 95% EUI reduction over the national institutional average and can be further reduced with additional (ongoing) commissioning efforts. Suggested improvements in operation include ensuring the electricity production is optimized and any faults corrected, dimming electric lighting when daylight is sufficient, extending the hours of natural ventilation, and better utilization of the hydronic radiant slab for thermal storage using predictive controls. This paper discusses the process followed in the design of the library, its key features, its early performance, and some of the lessons learned.