ANSI/ASHRAE/IES Standard 100, Energy and Emissions Building Performance Standard for Existing Buildings, is a code-ready building performance standard that provides processes and procedures for reducing energy consumption and carbon emissions through improved energy efficiency and performance of all types of existing buildings, including residential, commercial, institutional, and industrial. Standard 100 provides owners, utility companies, and government at every level a verifiable process that can reduce energy costs and support tax incentives, rebates, and related programs.

The 2024 edition brings numerous key updates to the standard:

• New metrics are provided for greenhouse gas emissions targets, along with continued improvements to energy efficiency and performance in existing buildings.
• Buildings are required to
  • Establish an energy management plan that incorporates efficient, low-carbon equipment into capital replacement
  • Achieve energy and emissions performance goals
  • Implement an operations and maintenance program to ensure continued building performance.
• Energy-efficient and low-emission buildings are provided a simple compliance mechanism to demonstrate compliance with the standard if they meet both energy use intensity (EUI) and greenhouse gas intensity (GHGI) targets.
• For buildings that do not meet targets, an energy audit and decarbonization assessment must be conducted, necessary measures must be implemented, and it must be demonstrated that measured EUI and GHGI targets are met. A separate compliance process is included for building types without targets.