CA001 Ravens Crossing

How a Community Went All-Electric

Lessons learned

• High performance windows as an envelope strategy can make heat recovery ventilators obsolete.
• Each occupant paying directly for their heating and cooling costs is likely to reduce future energy consumption but raised the construction costs.
• Even though the requirements were higher, constructions costs were comparable to other sites in the area.

Key facts

Description of the technical concept

Ravens Crossing is a 3,558 m2 (38,284 sq.ft.) residential development with 35 units, including 300 m2 (3,200 sq.ft.) of common space, a shared rooftop deck and garden, and a parking garage. To reduce energy consumption, some reliable design strategies were employed. These included positioning the building to take advantage of southern exposure, designing the south elevation with a high window-to-wall ratio to maximize solar heat gain, and specifying high-performance, triple-paned windows. The windows are from Starline’s 7100 series and the insulating glass units are filled with argon and include two low-emissivity coatings. The​​ average fenestration U-factor is 1.05 W/m2·K (0.18 Btu/h·ft2·F). The walls are constructed using 38 mm x 140 mm (2” x 6”) wood framing with batt insulation in the cavities, resulting in an effective RSI value of 2.82 m2·K/W (R-16). 

Each unit has its own Mitsubishi M-series horizontal-ducted heat pump for heating and cooling. The decision to use high-efficiency heat pumps (cooling SEER of 18, and heating HSPF of 12.6 (Region IV)) was based on reducing operating costs (compared to using electric baseboard heaters), quiet operation and providing cooling in the summer. Six small electric baseboard heaters were installed for supplementary heating in some areas of the basement and some rooms within the common area. Domestic hot water is generated by four A.O. Smith 450 L (120 US gallon) industrial electric water heaters.

With an all-electric design, the Ravens were initially concerned about the impact of power outages. After conducting research on the outage history, they determined that power reliability in the region was high. Given the unlikely scenario of a power outage, the Ravens decided to forgo the installation of a back-up power generator. If a power outage were to occur, the building envelope is likely to maintain a relatively stable indoor temperature for an extended period of time. 

Solar photovoltaic panels were initially considered to reduce operational costs and improve resilience to power outages, but to keep construction costs from escalating, they were not included in the project. Provisions in the electrical system and structural supports in the roof were added to facilitate the addition of solar panels in the future.

Results:

To ensure that the design would meet the standard’s performance target, an energy model was prepared by AME Group based on construction drawings. It was later updated to reflect as-built conditions. The updated energy model showed that the building is likely to be approximately 23% more energy-efficient than if it was built to meet the minimum requirements of Canada’s 2011 National Energy Code for Buildings (NECB). This level of energy efficiency allowed it to exceed the requirements for BUILT GREEN® Gold. 

The modelled total energy use intensity (TEUI) for the building is 108.5 kWh/m2 per year. Relative to the Energy Step Code, this TEUI meets Step 3 for large residential buildings in this climate zone. The thermal energy demand intensity (TEDI) for the building is 52.6 kWh/m2 per year. Comparing it to the Energy Step Code, this is less than Step 2.

The modelled greenhouse gas intensity (GHGI) is 1.2 kg CO2/m2 per year. What makes this GHGI especially impressive is that it was achieved by a building with moderate energy-efficiency measures. This result is a testament to the fact that the most effective path to deep and immediate operational emissions reductions is quite simple – build an all-electric building. As an aside, the GHGI for this building is low enough to meet the highest level of the Province’s upcoming Carbon Pollution Standard for new buildings. If this building was located in the City of Vancouver, it would meet its future carbon emissions limit of 3 kg CO2/m2 per year (effective July 1, 2023).