CBHCC seeking input on addressing embodied greenhouse gas emissions in the National Model Codes

To provide input on the draft policy direction:

  1. Review the content below.
  2. Submit comments to the CBHCC Secretary by email and attach any supportive material: CBHCCSecretary-SecretaireCCHCC@nrc-cnrc.gc.ca by July 14, 2025.

Introduction

This policy position paper presents the Canadian Board for Harmonized Construction Codes’ (CBHCC) approach on addressing embodied greenhouse gas (GHG) emissions for new houses and buildings in the National Model Codes. The purpose of this paper is to support the development of technical provisions in the 2030 code cycle. The draft direction enclosed focuses on embodied GHG emissions and was developed alongside the CBHCC’s 2025 code cycle work, which introduces a new GHG emission objective and technical requirements to address operational GHG emissions. Phase 1 provides initial direction. The CBHCC is considering expansion of scope to include other building elements and/or life cycle stages and performance evaluations metrics, and, as applicable, will provide further direction at a later date.

Background

The 2020 editions of the National Model Codes contain an energy efficiency objective and related requirements for the design and construction of new buildings and houses. The proposed 2025 edition of the National Energy Code of Canada for Buildings (NECB) and National Building Code of Canada (NBC) will also include an objective to address GHG emissions alongside technical requirements related to operational GHG emissions. Approximately 27%[1] of Canada’s GHG emissions are due to buildings. Embodied GHG emissions can account for up to 50%[2] of a new energy efficient building’s life cycle GHG emission. Minimizing excessive embodied GHG emissions in the National Model Codes will help reach GHG emission reduction goals. A life cycle assessment (LCA) is used to quantify a building element’s GHG emissions by evaluating the impacts at each stage of the building’s life cycle. The life cycle of buildings consists of four stages as shown in Figure 1.

Figure 1 – Life cycle phases of embodied GHG emissions.

Life cycle phases of embodied GHG emissions.

Text description of Figure 1This diagram illustrates the life cycle stages of a building as they relate to embodied greenhouse gas (GHG) emissions. It is divided into three main sections, outlined by a dashed line: Section 1. Embodied impact (in scope) Section 2. Beyond the building life cycle (out of scope) Section 3. Operational impact (out of scope) Section I – Embodied impact The Embodied impact section contains a sequence of four steps: Step 1: Product stage is outlined by a dashed red line labeled Embodied GHGe boundary considered in this document. This stage consists of three modules, visually represented by a series of vertically stacked red boxes.
  • Module A1: Raw material supply
  • Module A2: Transport
  • Module A3: Manufacturing
The visual distinction of this step represented by a separate outline, aligns with the policy position stating that the current focus is on modules A1–A3 of the life cycle, which are responsible for a significant portion of a building’s embodied GHG emissions. Step 2: Construction stage consists of two modules, visually represented by a series of vertically stacked orange boxes:
  • Module A4: Transport
  • Module A5: Construction and installation process
Step 3: Use stage consists of five modules, visually represented by a series of vertically stacked green boxes:
  • Module B1: Use
  • Module B2: Maintenance
  • Module B3: Repair
  • Module B4: Replacement
  • Module B5: Refurbishment
Step 4: End of life stage consists of four modules, visually represented by a series of vertically stacked blue boxes :
  • Module C1: Deconstruction/demolition
  • Module C2: Transport
  • Module C3: Waste processing
  • Module C4: Disposal
Out-of-scope sections – for context only Furthermore, as previously noted, two sections fall outside the scope of embodied GHG emissions considered in the policy paper, but are included for contextual purposes. Both of them are greyed-out to signify their status. Section Beyond the building life cycle is located to the right of the main i.e., Embodied impact section. It consists of four modules, visually represented by a series of vertically stacked light purple boxes:
  • Module D1: Recycling
  • Module D2: Reuse
  • Module D3: Energy recovery
  • Module D4: Exported energy
Section Operational impact is located below the Embodied impact section. It consists of two modules, visually represented by a series of vertically stacked light green boxes appearing as a continuation of Use stage modules (B1 to B5):
  • Module B6: Operational energy use
  • Module B7: Operational water use
Definitions
The following definitions are used in this document: Embodied GHG emissions[3] refer to the greenhouse gas emissions associated with materials and construction processes throughout the life cycle of a building excluding emissions from building energy use. This can include emissions from material extraction, manufacture, transportation, construction, replacement, refurbishment, demolition, removal. Life cycle is a term used in the context of assessing the overall environmental impact of buildings from the extraction of raw materials all the way to the disposal of waste at the end of their useful life. In the context of a building, it includes the product stage, construction stage, use stage and end-of-life stage. For the purpose of this policy position, operational impact and the Beyond the Building Life Cycle Stage D, is not in scope. The operational impact is addressed in the CBHCC’s policy paper on operational GHG emissions[4].

Draft policy direction for code development

Unless otherwise specified, the following are applicable to new construction only.
Tiered framework
Embodied GHG emissions National Model Code requirements should be developed in a tiered framework that allows jurisdictions to adopt changes at a pace that suits their needs while aligning on the overall approach and objectives. The tiered framework should incorporate progressively improved embodied GHG emissions performance targets within the parameters described below. In addition to the life cycle stages and building elements included below, the tiered framework should be able to accommodate the future addition of other life cycle stages and building elements and should provide options for a range of available construction materials. The parameters described below are based on the current state of knowledge and research in the subject area and reflects the availability of data that is suitable for development of National Model Code requirements in the 2030 code cycle. The CBHCC will continue ongoing policy discussions, which could inform future code development, on expanding the tiered framework described in this document to include a broader scope of life cycle stages, building elements, and/or GHG emissions metrics. The baseline level of the tiered framework should represent the minimum performance level that is attainable using construction materials and practices that are consistent with building elements associated with the lowest performing energy efficiency and operational GHG emissions tiers in the 2025 National Model Codes. Higher tiers of performance should include incremental improvements in performance over the baseline requirements. Where practical, the framework should leverage existing standards and guides.
Building elements and life cycle stages
When considering the impact of embodied GHG emissions on buildings elements, the National Model Codes should as a starting point have performance requirements for life cycle stages A1-A3 for the structural elements (including foundations and substructure), and, if practical within the code cycle, for the building envelope.
Performance evaluation metrics
Performance evaluation of embodied GHG emissions in the National Model Codes for the 2030 code cycle should include the percent-improvement (i.e. reference approach). The CBHCC will continue ongoing policy discussions, which could inform future code development, on expanding the performance evaluation to include both intensity (kg CO2 e/m2 of gross floor area) and absolute metrics (metric tons of carbon dioxide equivalent, MT CO2 e) and will provide further direction at a later date.
Prescriptive options
The scope of work should include prescriptive options for housing and small buildings (Part 9 of the National Building Code) that are available in the same edition of the National Model Codes as the tiered framework.
Geographical flexibility
The tiered framework should allow for flexibility to account for the unique circumstances of rural and remote areas.

[1] 18% operational GHG emissions including electricity-related emissions (source: Natural Resources Canada (2022). The Canada Green Buildings Strategy) and approximately 9% embodied GHG emissions (global estimate) (source: United Nations Environment Programme (2022). 2022 Global Status Report for Buildings and Construction: Towards a Zero-emission, Efficient and Resilient Buildings and Construction Sector).
[2] Embodied carbon emissions in buildings: explanations, interpretations, recommendations | Buildings & Cities 🗗
[3] National Whole-Building Life Cycle Assessment Practitioner’s Guide 🗗
[4] CBHCC Policy Positions on Developing and Implementing Greenhouse Gas Emissions Provisions in the National Model Codes 🗗