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Musings of an Energy Nerd

Understanding the Latest Energy Code

The 2021 IECC raises the bar on insulation levels and energy performance

The latest version of the most widely used energy code in the U.S. is the 2021 edition of the International Energy Conservation Code (IECC). The residential provisions of the 2021 IECC are also found in the 2021 International Residential Code (IRC). [Photo courtesy of International Code Council]

Most residential builders in the U.S. need to comply with a one of the International Codes. Energy provisions are found in the International Energy Conservation Code, or IECC; these energy-related requirements are also found in the International Residential Code, or IRC.

The International codes are updated every three years, and different states adopt newer codes at different rates. Some states are operating under the 2009 IRC, while others are operating under the 2015 IRC or 2018 IRC.

The latest version of the energy code is the 2021 IECC. As far as I know, no state has yet adopted the 2021 IRC or IECC, but it’s just a matter of time before some of them do. The 2021 IECC differs in several respects from its immediate predecessor, the 2018 IECC. So what’s new in the 2021 IECC?

There are various compliance paths

Residential builders can comply with the energy provisions of the 2021 IECC in various ways. There are four different compliance paths:

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