Zero Carbon Step Code Guide For BC Builders
A builder-focused guide to the BC Zero Carbon Step Code: greenhouse gas intensity (GHGI) targets, emissions factors, heat pump switchovers, and code timelines.
The Zero Carbon Step Code (ZCSC) is a performance-based regulation in the BC Building Code (Section 9.37 for Part 9, Section 10.3 for Part 3) addressing the operational carbon emissions of new buildings. Unlike the Energy Step Code, which regulates energy efficiency, the ZCSC targets the fuel types powering a building's heating, cooling, ventilation, and hot water systems. The framework establishes a clear path toward zero-carbon new construction by 2030 (EL-4).
The regulatory transition reached a major milestone on March 10, 2025 (under BCBC 2024 Revision 5), when EL-1 (measure-only) became mandatory province-wide. It is critical to distinguish this from the opt-in ZCSC framework under BCBC 2018 Revision 5 (effective May 1, 2023) to avoid permit-stage naming confusion. Every new permit application must now calculate and report its operational greenhouse gas intensity (GHGI). For in-stream projects permitted under earlier code versions, transition exceptions extend to March 8, 2027.
For Okanagan builders, navigating the ZCSC requires aligning mechanical specifications with the energy model early. In communities adopting EL-2 (Moderate Carbon) or EL-3 (Strong Carbon), heat pump space heating and electric domestic hot water (DHW) are the primary routes to compliance. Traditional gas-only systems become difficult to model, and Renewable Natural Gas (RNG) is currently modeled under standard fossil gas factors (0.18 kgCO2e/kWh), meaning it does not help meet compliance targets.
Understand the ZCSC levels from measurement to zero carbon.
- EL-1 (Measure Only): Calculate and report GHG/GHGI. Satisfied by standard Step Code compliance checklists.
- EL-2 (Moderate): Decarbonize principal heating system (prescriptive) or meet GHG/GHGI caps (performance).
- EL-3 (Strong): Decarbonize principal heating and domestic hot water systems, or meet performance caps.
- EL-4 (Zero Carbon): Decarbonize all building systems, equipment, and appliances (except controlled redundant backup).
Know what emissions count toward compliance.
- Calculated from space heating, space cooling, ventilation, and domestic hot water (same as MEUI).
- Excludes plug loads, lighting, and ancillary end-uses like decorative gas fireplaces, gas cooktops, and gas laundry dryers.
- Electricity factor is set by the BCBC at 0.011 kgCO2e/kWh; natural gas is set at 0.18 kgCO2e/kWh.
- Table 9.37.1.3 offers two performance options: Option 1 (absolute total-GHG cap only) for smaller homes, and Option 2 (both total-GHG and GHGI caps) for larger homes.
- Renewable Natural Gas (RNG) is modeled at 0.18 kgCO2e/kWh; the BCBC does not currently recognize RNG as a distinct low-emissions fuel.
Control your backup heating to protect your emissions score.
- Sentence 9.36.3.6.(6) requires controls that prevent a supplemental heater from running when the heat pump can meet the load.
- Model-derived heat-pump switchover (balance-point) temperature must match the installed site controls.
- If supplemental heat is gas, setting the switchover wrong on-site will increase emissions and can fail the target EL.
- Log and verify the switchover temperature in mechanical commissioning documentation to align with the HOT2000 model.
Lock down heating and hot-water specifications early.
- Verify the local municipality's adopted ZCSC level before submitting drawings.
- Determine if the project will use the prescriptive path (equipment requirements) or performance path (energy model).
- Review how heating and hot-water systems are classified; consult the AHJ on backup or secondary systems.
- Group energy modeling, F280 calcs, and mechanical ventilation early to avoid permit delays.
What builders ask before booking.
What is the Zero Carbon Step Code?
It is a BC Building Code regulation (Section 9.37) targeting the carbon intensity of building operations. It regulates fuel types to reduce greenhouse gas emissions, operating alongside the Energy Step Code.
Is Zero Carbon Step Code mandatory in BC?
Yes, EL-1 (measure-only) is mandatory province-wide for all new Part 9 building permits applied for on or after March 10, 2025, under BCBC 2024 Revision 5. Local governments can opt into higher tiers (EL-2 to EL-4).
Why are there two different "Revision 5" references in BC code discussions?
Industry literature references two different "Revision 5" packages: (1) BCBC 2018 Revision 5 (effective May 1, 2023, which introduced the opt-in ZCSC), and (2) BCBC 2024 Revision 5 (effective March 10, 2025, which made EL-1 mandatory province-wide). Always verify the base code year on the permit application.
How does a small home pass the ZCSC performance path?
Under BCBC Table 9.37.1.3, smaller homes can comply via Option 1, which requires meeting a total annual GHG cap only. Larger homes generally use Option 2, which requires meeting both a total-GHG cap and a GHGI (intensity per square meter) cap.
Can I use Renewable Natural Gas (RNG) to pass the Zero Carbon Step Code?
No. The BCBC does not currently recognize RNG as a separate low-carbon fuel. A home plumbed for RNG is still modeled at the standard natural-gas factor of 0.18 kgCO2e/kWh.
What systems are included in the GHGI calculation?
The calculation includes emissions from space heating, space cooling, domestic hot water, and ventilation systems. It excludes cooking, laundry, lighting, plug loads, and decorative fireplaces.
Send the drawings and project basics.
Jesse Cummings reviews the file and returns a quote - base compliance package and applicable add-ons, priced by stage - within one business day after receiving the drawings and project basics.