In practice, there are a variety of ways to meet the top level of the Zero Carbon Step Code. It is entirely at the designer or architect’s discretion to choose how the building will meet a target Emission Level (EL). Decisions on energy sources and equipment may affect requirements for other building systems and components (such as insulation, windows, etc.).
Homes and small residential buildings (Part 9) have both performance and prescriptive compliance options available. Large complex buildings (Part 3) only have a performance pathway available, where compliance is determined by following the City of Vancouver Energy Modelling Guidelines.
Under the performance pathway for Part 9, the EL is determined by modelling the building and its systems to meet certain metrics. These metrics are the same for all buildings that fall under the Zero Carbon Step Code, independent of the energy source chosen for building systems and equipment. This means that some trade-offs – such as a higher performing envelope – may have to be included in the building design if energy sources with a higher emissions factor* are used. The greenhouse gas emissions of ancillary equipment such as cooktops, fireplaces, and laundry drying equipment are not included in the modelling of a Part 9 building’s EL for determining compliance with the performance path. As it is a performance based compliance pathway, there is no simple archetype of an EL-4 building, as one can be different from the next depending on design decisions made for each building.
The prescriptive pathway for Part 9 is a simplified option to meet an EL which may require energy sources with a low emission factor (≤0.011 kg CO2e/kWh) for building heating systems, service hot water systems, equipment, and/or appliances. An EL-4 prescriptive building uses low-carbon energy sources for all building systems, equipment, and appliances. Cooktops and laundry drying equipment are included in the prescriptive path compliance, and must use energy sources with a lower carbon emissions factor to meet EL-4 under this pathway.
For Part 3 buildings the performance pathway is similar to Part 9, however building’s greenhouse gas emissions are calculated based on the use of all energy utilities on site regardless of what equipment/appliances are being served. This would include all building systems, equipment, and appliances in the performance model. Like Part 9, there may be design trade-offs required if energy sources with a higher emissions factor are predominantly used throughout the building. As it is performance based compliance there is no simple archetype of an EL-4 building, as one can be different than the next depending on design decisions made for each building.
*The emissions factors associated with the use of energy utilities consumed by the building’s systems are published in the BC Building Code as follows:
1) 0.011 kg CO2e/kWh for electricity, and
2) 0.180 kg CO2e/kWh for natural gas.
Further detailed information on the Zero Carbon Step Code can be found in Technical Bulletin No. B23-03 from the provincial Building and Safety Standards Branch, including emissions factors for other energy sources.