REDUCTION OF EMBODIED GHG EMISSIONS IN THE 2027 IBC
In April 2025 the ICC Committe proposed changes to the I-Codes that would codify required reductions in GWP. The changes will be in a new voluntary appendix (Appendix Q) to the 2027 IBC, and can be adopted by local jurisdictions.
Overview of Appendix Requirements
This proposal adds a new voluntary appendix to the International Building Code (IBC), which may act as a reference for jurisdictions wishing to establish code methods to measure and reduce the embodied greenhouse gas (GHG) emissions impact of building materials.
Appendix Q provides criteria for the production and submission of environmental product declarations, building life cycle assessment, and proof of building reuse for a building project.
In sum, the appendix provides a requirement for construction document submittals to include reporting on the embodied GHG emissions associated with proposed projects over a choice of 50,000 or 100,000 square feet, as determined by the AHJ. Project teams must choose one form of documentation from the following three options:
1. Product compliance pathway: submit product or facility-specific environmental product declarations (EPDs) for covered products that indicate that the global warming potential (GWP) meets a certain percentage – as determined by the AHJ – of the industry average GWP of the product.
2. Building compliance pathway: submit a building life cycle assessment (LCA) for the building’s structure and enclosure that indicates a percent-reduction – as determined by the AHJ – in GWP from 102 lbCO e/square feet (500 kgCO e/m2) or compared to an industry-average baseline.
3. Building reuse pathway: submit proof of reuse of at least 45% of an existing building’s structure and enclosure.
Finally, the proposed appendix aims to provide a clear and simple path for code officials to determine compliance at two points along the project timeline: at the initial submission of construction documents and at the subsequent submission of amended construction documents. The role of the code official is to check for the submission of required documentation, confirm that requirements were met, and verify that the registered design professional has signed off on meeting these provisions. These efforts that fall on the design professional as well as the code official are anticipated to require minimal effort.
DOCUMENTATION
Prepared by a registered design professional.
Any changes to the products shown on the construction documents versus the as-built products require that the GWP calculations be updated and attested to by the registered design professionsal.
DISCUSSION
This code revisions is a positive step to codify embodied carbon reductions in buildings. However, there are several unique issues created with this code revision:
The AHJ needs to realize that 2027 code changes will effect buildings being completed 2-4 years later and select the % reductions of the material compliance or building compliance accordingly in order to ensure that reductions are on a pathway for annual changes in the 8-10% range.
The material compliance pathway will require extensive material takeoffs and collection of EPDs by the design team, and may force design teams to begin providing LCAs.
The building compliance pathway that allows comparison with an equivalent building requires a considerable amount of additional work and the term “equivalent building” is open to multiple interpretations.
The building compliance pathway that requires meeting a certain % of 500 kgCO2e/m2 has several extenuating issues:
a. This value is too high for many building types (e.g. wood-framed multifamily and office buildings, simple low-rise buildings), and too low for other building types (e.g. recreation and aquatic centers, hospitals, labs, stadiums, high-rise). This one-size-fits-all approach will be difficult to work with and may not achieve the desired effect.
b. The scope is defined as structure and enclosure as a minimum, and allows interiors to be added. The scope chosen for an LCA has a high impact on the results. LCAs performed by different companies will use different scopes. Whole building LCAs, which will include structure, enclosure, interiors, MEP, FF&E, and site are what the top firms are progressing towards. This pathway may require firms to prepare two LCAs, one with their best practices scope and one scaled-back to a structures and enclosures scope.
The documentation requirement that the construction documents must have the same products as the final building will make fully modeled as-builts mandatory.