This fact sheet produced by ACEEE details why HUD’s proposal to update the referenced energy codes to the 2021 IECC/ASHRAE 90.1-2019 is so important.

International Energy Conservation Code
The IECC is referred to as a model energy code* because building codes are state or local laws; there is no national building energy code in the US. Regardless of when any state adopts a code, every three years, the IECC is updated to incorporate new building technologies and practices as they evolve over time, and ensure that new American homes and commercial buildings meet modern-day minimum levels of efficiency. In previous cycles, officials from municipalities and states across the nation voted on the proposed changes; starting with the 2024 IECC, the code is determined by committee members, representing nine different categories, including governmental regulators.
The IECC serves as the go-to source for states adopting an energy code; an ICC code is in use or adopted in all 50 states and beyond. That’s why it’s important to get each three-year version right, so that states can be confident they’re adopting an updated, well-vetted, and feasibly implementable building energy code.
*The IECC is the model residential energy code in the US; for commercial buildings, ASHRAE 90.1 is considered the model code, though the majority of states adopt the commercial IECC with the option to comply via ASHRAE 90.1.
History of the International Energy Conservation Code
For nearly two decades, successive versions of the IECC and its predecessor, the Model Energy Code (MEC), made only 1 to 2 percent gains in energy efficiency. That changed in 2009 and 2012, when the Energy-Efficient Codes Coalition (EECC) brought together government and business leaders, regional energy efficiency alliances, academics, think tanks, utilities, conservation groups, low-income housing groups and energy consumers to support a 30+ percent energy efficiency boost, as can be seen in the adjacent graph.
After the progressive gains made to the 2009 and 2012 IECCs, progress stalled as anti-efficiency lobbyists successfully halted further progress during the 2015 and 2018 code cycles. These lost opportunities for efficiency gains in the 2015 and 2018 IECCs set us behind and have cost homeowners and business owners thousands in lost revenue due to buildings being constructed to weaker standards than is feasible today.
The 2021 code cycle once again resulted in significant progress, with an efficiency boost of more than 10% over the 2018 IECC.
Energy Code Timeline
Additional Resources
IMT’s Cherylyn Kelley explores why the HUD proposal to reference the 2021 IECC is such a Big Deal.
Recommendations regarding select public comments submitted on the 2024 IECC Residential draft during the first public comment period in Fall 2022.
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