Latest ASHRAE Energy Efficiency Standard for Existing Buildings


ASHRAE has released the latest version of its energy efficiency standard for existing buildings, with an expanded focus to incorporate building decarbonization. 

ANSI/ASHRAE/IES Standard 100-2024, 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. The latest edition of the standard includes carbon emissions performance requirements for existing buildings, as well as emissions targets for dozens of building types.

“As the demand grows for reduced energy use and carbon emission in existing building, there has been heightened interest in Standard 100 within the past year for its potential to shape building regulations on an expanded level,” said 2023-24 ASHRAE President Ginger Scoggins, P.E., Fellow ASHRAE. “The development of this revised standard underscores our commitment to advancing sustainability measures and responding to the evolving needs of the industry.”

Key updates to the standard are as follows:

  • New metrics provided for establishing greenhouse gas emissions targets, along with continued improvements to energy efficiency and performance in existing buildings.
  • Building requirements to: 
    • Establish an energy management plan incorporating efficient, low-carbon equipment into capital replacement.
    • Achieve energy and emissions performance goals 
    • Implement an operations and maintenance program for continued building performance.
  • Simple compliance mechanism for energy-efficient and low-emission buildings.
  • Energy audit and decarbonization assessment and a separate compliance process for building types that do not have energy or emissions targets.
  • Guidance for jurisdictions seeking to develop their own energy consumption and/or greenhouse gas emissions targets. 



Founded in 1894, ASHRAE is a global professional society committed to serve humanity by advancing the arts and sciences of heating ventilation, air conditioning, refrigeration and their allied fields. For more information, visit