The Building Decarbonization Code is a groundbreaking tool aiming to deliver carbon neutral performance. The Version 1.2 code language from NBI serves as a building decarbonization overlay to the 2021 International Energy Conservation Code (IECC) and is now compatible with ASHRAE 90.1. It is designed to help states and cities working to mitigate carbon resulting from energy use in the built environment, which accounts for 39% of U.S. emissions.