ANSI/ASHRAE/IES Standard 90.1-2019: Energy Standard for Buildings Except Low-Rise Residential Buildings
About this book
ASHRAE Standard 90.1, officially titled "Energy Standard for Buildings Except Low-Rise Residential Buildings," is the most widely used and cited building energy code in the United States and one of the most influential internationally. Published by ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers), it establishes minimum energy efficiency requirements for the design and construction of new commercial, industrial, and high-rise residential buildings, as well as for major renovations of existing buildings. The standard was first published in 1975 as a response to the 1973 oil crisis, and has been updated on a roughly three-year cycle ever since.
Each successive edition has tightened energy requirements as technologies and best practices have advanced. The 2016, 2019, and 2022 editions represent significant milestones in this progression, each delivering substantial reductions in allowable energy use compared to predecessors. The standard is organized into chapters addressing: building envelope (walls, roofs, windows, and their thermal and solar performance requirements); HVAC systems (heating, ventilation, and air conditioning equipment efficiency, controls, and system design); service water heating; lighting (both interior and exterior power densities and controls); other equipment; and compliance paths including the prescriptive approach and the energy cost budget method.
A particularly important section is Appendix G, the Performance Rating Method, which provides a standardized baseline simulation methodology for demonstrating above-code performance. Appendix G is extensively used in green building certification programs, particularly LEED, where building designs must demonstrate a percentage improvement over the Appendix G baseline. It is also the basis for the ASHRAE Building Energy Quotient (bEQ) and similar rating programs.
ASHRAE 90.1 is referenced as the mandatory compliance standard in the International Energy Conservation Code (IECC), and has been adopted by reference in the building codes of most US states and many local jurisdictions. Internationally, it has influenced the development of energy codes in Canada, Russia, China, South Korea, and numerous other countries. The US Department of Energy is required by law to certify that each new edition of ASHRAE 90.1 represents greater energy efficiency than the previous edition.
The 2019 edition (referenced by both ANSI/ASHRAE/IES 90.1-2019 entries in this database) achieved approximately 4.7 percent better energy performance compared to the 2016 edition for new commercial buildings, according to DOE analysis. Improvements were concentrated in lighting power densities, HVAC efficiency requirements, envelope performance, and the introduction of new requirements for high-performance sequences of operation. The 2022 edition extended these gains further, incorporating requirements that align more closely with net-zero energy building targets.
The standard is developed through a continuous maintenance process involving standing project committees, public reviews, and formal balloting by the ASHRAE membership. The "IES" co-sponsorship since the 2010 edition reflects the Illuminating Engineering Society's formal participation in developing the lighting provisions, which have become among the most technically sophisticated in the standard. Sources: ASHRAE official website (ashrae.org); US Department of Energy Building Energy Codes Program (energycodes.gov); ASHRAE Standard 90.1 User's Manual; PNNL analysis reports for DOE.