Member Knowledge Centre
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The Knowledge Centre provides CHBA members with access to information and resources. It is a growing resource that is currently focused on updating members about national building code information. Please note that this information is a benefit of your membership, and should not be shared beyond your company/organization.
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Understanding the New Requirements for Operational Greenhouse Gas Emissions
Understanding the New Requirements for Operational Greenhouse Gas Emissions
Understanding the New Requirements for
Operational Greenhouse Gas Emissions
Operational Greenhouse Gas Emissions or opGHG refer to gases released during a building's operation over its entire lifetime from the energy used for space heating and cooling, and water heating. For the first time, the 2025 National Building Code (NBC) has introduced requirements aimed at reducing opGHG emissions from new buildings. To reduce these emissions, new homes will have to meet defined performance levels related to their expected opGHG output. This applies across all regions of the country and is intended to push the market toward lower-emission design choices while allowing flexibility in how those outcomes are achieved.
Technical Concepts
GHG Emissions Performance Levels: (National Codes) Emission Factors: | |
Compliance Methods
To meet the opGHG requirements, builders can choose from two different compliance methods in Part 9, each offering varying levels of simplicity and flexibility:
Prescriptive Path the target performance level can be achieved based on the location's grid emission factor, the selected energy equipment for the home (e.g., water heater, furnace/ heat pump) and their respective energy sources and the minimum number of Energy Conservation Points that the home achieves under the energy efficiency requirements in 9.36.9.
Performance Path The annual GHG emissions calculated for both the proposed and reference building models, then compared using either the percentage of target or percent improvement to assess performance level compliance.
Prescriptive Path via the Energy Conservation Points Method
One starting point for builders is to begin by selecting the desired performance level (from A to F) for their home design. Each Performance level has a dedicated Table in the code. The design options for the desired level then depend on the location's grid emission factor. Using the respective table for the desired level, the builder can select the type of space and water heating equipment with their respective energy sources. The energy conservation points for the entire home can then be established by following Subsection 9.36.9 the 2025 NBC. Although the prescriptive table offers several compliance options for each performance level, the grid emission factor (GEF) requirements effectively exclude provinces with high GEF values from meeting better performance levels. For example, achieving Level B requires a maximum allowable GEF of 100, while Alberta s GEF is 181, making compliance with Level B impossible. The best achievable rating for a new home in Alberta is therefore Level C using the prescriptive method. | |
Performance Path via the Percent Improvement Method
The performance path uses the reference-vs.-proposed concept in conjunction with the energy model data for the same home.
To obtain the Total Annual Emissions of the Reference House:
- Annual space heating energy is multiplied by 235,
- Annual water heating energy is multiplied by 260
- Annual ventilation and cooling energy is multiplied by the GEF of the province where the house is located
- All of these values are then added and divided by 1,000
For the Total Annual Emissions of the Proposed House the annual energy used in each of these categories (ventilation, cooling, heating, water heating) is multiplied by the emission factor corresponding to the respective fuel type of the equipment.
It is important to note that emission factors are taken first from provincial sources; if these are not available, utility-issued factors are used. Only when neither of these sources provides data are the emission factors from the NBC Table 9.36.11.6.-A are applied (see page 1)
Example
Table 1 below is an example of a Net Zero home in Saskatchewan, which has a grid emission factor of 146.6 g CO2e/kWh and a utility gas emission factor of 185 g CO2e/kWh. These values were selected from NBC Table 9.36.11.6.-A for simplicity. |
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Once these values are calculated, the performance level is determined by dividing the emissions of the proposed house (1,225 kg CO2e) by those of the reference house (6,784 kg CO2e). In this case, the result is 0.18, indicating that the proposed house achieves an 82% reduction in GHG emissions compared to the reference house, which corresponds to Performance Level B. |
What about reducing emissions via solar PV panels?
Although solar photovoltaic (PV) energy equipment installed on homes constitutes a zero-emission energy source, the installation of PV panels is not recognized by either compliance method to reduce opGHG emissions in homes. This exclusion of on-site renewable energy from operational GHG calculations reduces design flexibility for builders, inflates reported emissions for homes with PV panels, and can force unnecessary costly upgrades in insulation to reach higher energy tiers and GHG levels that would not be necessary if the emission reductions from PV sources were recognized. Builders who want to integrate solar PV in their homes will have to work with local authorities to have the emissions reductions from PV panels counted. Table 1 shows how many emissions in kg CO2e solar panels can reduce a home's annual operational GHG emissions based on the NBC electrical emission factor of the province, in which the home is located. The table was developed using research from CHBA and Volta Snap's net-zero homes studies, assuming a worst-case annual solar output potential of 964 kWh/kW for standard 5 kW and 10 kW south-facing systems. This method can be used to estimate the GHG savings from PV systems by region. If available, provincial or utility emission factors can be applied by multiplying the total estimated energy produced by the PV system with the local electricity grid emission factor. This calculation would provide the total emission savings resulting from PV energy production that could be reduced from a home's operational GHG emissions. | |
Climate Resilience
For the highest performance levels A and B, the prescriptive code compliance only allows fully electric homes and shifts even supplemental heating to fully electric. While this may reduce emissions in many provinces, it also comes at a cost of less energy resilience. This applies particularly in rural areas that often face longer power outages after extreme climate events and requires heating systems that can reliably operate on modest backup power such as battery storage systems. A gas furnace typically needs only 300 700 W of electricity to run its blower and controls, compared to the several kilowatts often required by electric resistance heaters or cold-climate heat pumps, which makes electric-only systems more difficult to sustain during extended outages.
Furthermore, CHBA data from over 1,200 gas heated Net Zero homes show an average of 80% opGHG reduction (Level B) under the performance path, but the same homes, due to using gas, would drop to Level C prescriptively. This means homes built under the prescriptive path can appear less efficient than equivalent homes under the performance path, despite delivering similar or better real-world results.
As CHBA continues to demand that code committees reconsider the inclusion of zero-emission energy sources like solar PV to provide a fair assessment of a home s true opGHG emissions and reward builders pursuing practical energy efficiency and carbon emission saving paths, builders can make their case to the local authorities.
Additional Info
Download File : opGHG backgrounder.pdf