2024 International Energy Conservation Code

The International Energy Conservation Code (IECC) developed by the International Code Council (ICC) is a model building code that sets minimum efficiency standards in new construction for a structure’s walls, floors, ceilings, lighting, windows, doors, duct leakage, and air leakage. It is the most adopted energy code in the country and is recognized as the national model energy code for low-rise residential buildings.

ICC published the 2024 edition of the IECC on Aug. 14, 2024. Historically, the IECC has followed the same code development process as other model building codes. Beginning with the 2024 IECC, ICC changed the procedures so that it now follows a standards development process, where the final decisions rest with consensus committees, not governmental voting members. Now, two consensus committees – one for the commercial provisions and one for the residential provisions – are tasked with updating the energy code.

NAHB was represented on both committees by a small group of NAHB builder members and NAHB staff who devoted significant time and effort to ensure the new energy will prioritize cost-effectiveness and consumer benefits, maximize design choices for builders, and can be practically implemented in the field. These individuals continue their work on these bodies to develop the next edition of the code, the 2027 IECC.

The U.S. Department of Energy (DOE) issued a determination on the 2024 IECC showing that it achieves a 7.8% site energy savings and 6.6% energy cost savings compared to the previous edition, the 2021 IECC. Although the 2024 IECC will achieve incrementally higher energy savings than the 2021 edition, the residential provisions will offer substantially more flexibility and a wider range of options for builders to achieve compliance. Among the most significant changes to the residential provisions:

• Ceiling insulation requirements are returning to levels from the 2018 IECC, and additional design flexibility is included for wall insulation in Climate Zones 4 and 5.
• The prescriptive compliance path will require additional efficiency practices from a list of dozens of measures with assigned credits.
• The performance compliance path has been updated and expanded to allow once again for equipment trade-offs and to recognize duct location.
• The Energy Rating Index (ERI) compliance path has been updated to improve its usability.
• Provisions for existing buildings have also been substantially updated.

The 2024 IECC also includes appendices (which states and municipalities can choose to adopt to be part of the mandatory requirements in their jurisdiction) developed to address state and local goals for electrification and even higher levels of performance, including options to achieve zero net energy in residential and commercial buildings.

NAHB is providing resources in the 2024 IECC Residential Code Adoption Kit to help builders and state and local HBAs navigate the new model energy code requirements. The kit includes:

• List of significant changes from the 2018 IECC to the 2024 IECC residential provisions and from the 2021 IECC to the 2024 IECC
• Cost analysis of the 2024 IECC code changes by Home Innovation Research Labs, which shows significant cost savings for the 2024 IECC compared to the 2021 IECC in many, but not all, climate zones.
• List of recommended amendments to 2024 IECC supported with substantiating information
• List of items to consider before adoption of 2024 IECC Appendices
• A summary table with the status of state adoption of different editions of the IECC around the country