ANSI/ASHRAE/IES Standard 100-2024: Energy Efficiency in Existing Buildings

The American National Standard for energy efficiency in existing buildings, ANSI/ASHRAE/IES Standard 100, has been revised.

New buildings continuously emerge. New indoor environments are introduced to the world, and existing buildings are demolished to make space for new ones. Since the late Seventies, the number of U.S. commercial buildings has increased by around 50 percent. Worldwide, skyscrapers, surely the largest of buildings, have been sprouting up in higher numbers than ever before. In fact, 2023 set a record for the most new skyscrapers in one year.

Newly constructed buildings, regardless of purpose or size, generally benefit from more advanced technology and practices when compared with older buildings. This includes, of course, energy efficiency, a key concern when it comes to saving energy and money and striving for sustainability. On a grand scale, such an issue should not be overlooked, as buildings comprise 40 percent of the total energy consumption in the United States.

However, more often than not retrofitting an existing building is more environmentally friendly and cost effective than knocking it down and constructing anew.

What Is ANSI/ASHRAE/IES Standard 100-2024?

ANSI/ASHRAE/IES Standard 100-2024 sets criteria to reduce energy consumption through improved energy efficiency and performance in existing buildings. It applies to existing buildings, portions of buildings, and building complexes, including the envelope and all systems. The standard, however, excludes industrial and agricultural processes in buildings for which the energy targets do not include these processes.

Overall, ANSI/ASHRAE/IES Standard 100-2024 is purposed with increasing the energy efficiency of systems and components and upgrading the thermal performance of the building envelope. It provides procedures and programs crucial to energy efficient operation, maintenance, management, and monitoring.

In any building, energy consumption takes place in different forms, so assuring efficiency as part of the indoor environment confronts numerous facets of the various systems and practices. In fulfilling this responsibility, ANSI/ASHRAE/IES Standard 100-2024 details guidelines for operation and maintenance and energy use, as well as an energy management plan and the methods of implementation and verification. It details information relevant to residential and nonresidential buildings.

Changes to ANSI/ASHRAE/IES Standard 100-2024

ANSI/ASHRAE/IES Standard 100-2024 revises the previous edition of the same American National Standard for energy efficiency in existing buildings that was released in 2018. Some notable changes made to this standard include:

• Title, purpose, and scope were revised to position the standard as a model building performance standard (BPS) that includes performance requirements for carbon emissions, in addition to energy efficiency, for existing buildings.
• Requirements for greenhouse gas emissions were added to the existing energy efficiency requirements.
• An emissions GHG monitoring methodology was defined, and GHG targets were established.
• An Informative Appendix J, “Guidance for Locally Derived Building Performance Targets,” was added to provide guidance to jurisdictions seeking to develop their own energy targets based on local energy or emissions data.
• U.S. regional energy conversion factors were added to the normative section of the standard that pro vides authorities having jurisdiction with the option to use regional U.S. energy conversion factor values
  for electricity.
• EUI targets were updated with 2012 Commercial Buildings Energy Consumption Survey (CBECS) and
  2015 Residential Energy Consumption Survey (RECS) data. This update includes two new commercial
  building types (courthouse/probation office and bar/pub/lounge) as well as the three newest ASHRAE
  climate zones (0A, 0B, and, 1B).

ANSI/ASHRAE/IES Standard 100-2018: Energy Efficiency in Existing Buildings is available on the ANSI Webstore. This American National Standard was developed and published by ASHRAE. For any questions regarding its technical contact, please reach out to ASHRAE. You can find their contact information here: Who to Contact for Standards Related Questions.

Changes to ANSI/ASHRAE/IES 100-2018

For any past users of this standard, some of the major changes made to ANSI/ASHRAE/IES Standard 100-2018 included:

• Normative primary energy EUI target tables are provided in Sections 7, “Energy-Use Analysis and Target Requirements,” and 10, “Residential Buildings and Dwelling Units,” and in Normative Annex A, “Alternative Energy Intensity Targets,” along with a primary energy EUI calculation option in Annex A, to add an alternative compliance path for the qualified person seeking compliance with the standard
• Energy audit guidelines for buildings without energy targets are clarified by qualifying when a Level 1 audit can be used to comply with the standard
• New Informative Annex M, “Guidance on Building Type Definitions”
• Incorporation of Addenda a, b, c, and d to ANSI/ASHRAE/IES Standard 100-2015, the description information for which is given in Informative Annex N