The newly released Building Performance Standards (BPS): A Technical Resource Guide was created to provide a technical basis for policymakers, building owners, practitioners and other stakeholders interested in developing and implementing a BPS policy. The first in a series of seven guidebooks by ASHRAE on building decarbonization, this guide focuses on reducing building operating energy use and resulting emissions in existing commercial and multifamily buildings, as established by leading U.S. cities and states. Jointly developed by ASHRAE, the U.S. Department of Energy (DOE) and its national laboratories, the BPS guide is meant to provide the information needed to make informed policy design decisions that drive deeper existing building decarbonization and provide equitable outcomes for all involved.