Key Changes in the 2021 IECC for the Northeast and Mid-Atlantic

The 2021 International Energy Conservation Code (IECC) is regarded by many as a significant achievement in building energy efficiency compared to the prior two code cycles (IECC 2015 and IECC 2018). Based on early industry estimates, residential construction would gain an 8-14 percent increase in efficiency (depending on climate zone). For commercial construction, estimates suggest improvements in energy efficiency of around 10 percent. Since buildings account for approximately 40 percent of greenhouse gas emissions in the United States, an energy code that provides significant energy efficiency improvement is a substantial advancement for the building sector, especially as states aim for higher levels of energy efficiency and a reduction in emissions. This resource is an overview of the major changes in IECC 2021 and is not intended to cover all changes within the code. For official code resources, please visit:

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