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ANSI/ASHRAE/IES Standard 90.1

Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings

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Standard 90.1

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About Standard 90.1

ANSI/ASHRAE/IES Standard 90.1, Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings has been a benchmark for commercial building energy codes in the United States, and a key basis for codes and standards around the world, for almost half a century. This standard provides the minimum requirements for energy-efficient design of most sites and buildings, except low-rise residential buildings. It offers, in detail, the minimum energy efficiency requirements for design and construction of new sites and buildings and their systems, new portions of buildings and their systems, and new systems and equipment in existing buildings, as well as criteria for determining compliance with these requirements. It is an indispensable reference for engineers and other professionals involved in design of buildings, sites, and building systems.

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What’s New in Standard 90.1

The 2025 edition of Standard 90.1 continues ASHRAE’s efforts to improve energy efficiency for commercial buildings and sites. The standard incorporates 105 addenda that advance levels of energy efficiency, expand options for compliance, and better align with industry practice and related ASHRAE standards. Click below to see what’s new.


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General

  • Revised, more consistent flowcharts that better illustrate key system requirements
  • Online access to climate zone tables via a free-to-read version of Standard 169
  • New and updated supporting tools
  • Updated normative and informative references

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Enforcement and Compliance (Section 4)

  • Unified and simplified terminology for jurisdictional authority
  • Clarified commissioning requirements
  • Updated building performance factors (BPF) for use with Appendix G

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Building Envelope (Section 5)

  • Updated insulation levels for opaque elements (walls, roofs, and floors) and fenestration (windows and skylights) to increase envelope stringency
  • Clarified fenestration provisions to allow for performance impacts at high elevations
  • New requirements for the proper installation of rigid insulation boards
  • Updated methodology for calculating effective U-factors for steel-framed walls and where continuous insulation is interrupted

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Mechanical (Sections 6 and 7) 

  • Increased minimum efficiency requirements for a wide range of equipment to reflect the latest federal test procedures and industry rating standards for products that include unitary systems, water-source heat pumps, cooling towers, fans, and dedicated outdoor air systems
  • Updated annualized metrics that focus more on average annual efficiency:
    • New metrics for unitary products with the new IVEC cooling annualized metric, and a new annualized metric for heat pumps with an IVHE for warmer climates and IVHEC for cold climates
    • A new IEER for water-source heat pumps
  • Integrated DOE regulated products tables to improve presentation
  • New procedure for fan system power limits emphasizing distribution system efficiency
  • Revised pool heating provisions to prioritize recovered and renewable heat sources before conventional heating methods are engaged
  • New provisions for gas-fired heat pumps and gas-fired heat pump-water heaters to meet prescriptive requirements and qualify for energy credits
  • Updated dehumidification and ventilation requirements to align with ANSI/ASHRAE Standard 62.1

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Power and Lighting (Sections 8 and 9)

  • New provisions for electric vehicle spaces, receptacle controls, and energy monitoring
  • New requirement, where direct digital control systems are installed, for data to be graphically displayed to encourage effective monitoring of building energy use
  • Restructured lighting requirements to clearly distinguish lighting power density limits from control requirements, and updated interior and exterior lighting power density values
  • Revised decorative and specialty lighting values to reflect widespread LED adoption
  • Revised exterior lighting zones to align with current IES guidance
  • Strengthened control requirements through expanded daylight-responsive controls, updated occupancy provisions, and revised thresholds that trigger automatic control requirements

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Renewable Energy (Section 10)

  • Expanded and clarified renewable energy provisions, including higher minimum prescriptive on-site renewable capacity requirements based on an updated cost-effectiveness analysis, and the introduction of limited off-site renewable energy compliance options by climate zone

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Energy Credits (Section 11)

(Energy credits, first introduced in 2022, were intended to give a flexible prescriptive requirement for additional efficiency measures by requiring a minimum number of additional points for efficiency measures from various categories.)

  • Improved flexibility and performance-oriented structure of energy credit framework
  • Added new credits for system-level strategies, including use of the Mechanical System Performance Rating Method (TSPR) and thermal energy storage for both heating and cooling
  • Increased the overall number of credits required by building type based on updated analyses that considered real-world performance factors

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Energy Cost Budget (ECB) (Section 12)

  • Refined the ECB compliance path to improve consistency with prescriptive requirements
  • Updated modeling rules to align envelope, mechanical, and lighting assumptions in the budget building more closely with Section 5, 6, and 9 requirements
  • Added requirements that, where available, actual utility rates or contractual energy prices must be used instead of generic national averages
  • Altered modeling of fan power in baseline systems due to changes in equipment efficiency metrics and rating conventions
  • Further refined ECB requirements with respect to building orientation, shading assumptions, and treatment of renewable energy

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Appendix G—Performance Rating Method

  • Made significant updates to reinforce Normative Appendix G as a stable, transparent performance baseline, while accommodating modern design approaches
  • Expanded and refined baseline HVAC system definitions, including new distinctions based on heating source and updated zoning and economizer rules
  • Revised modeling requirements for elevators, dehumidification, ventilation, and purchased heating and cooling to better reflect measured energy use and current international standards
  • Updated simulation software requirements to align with the latest version of ASHRAE Standard 140
  • Replaced references to specific simulation tools with performance-based qualification criteria
  • Updated building performance factors in consideration of the energy efficiency improvements introduced since the last edition

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Optional Appendices for Alternative Measures of Compliance

(Informative Appendices M, N, and O)

To meet the requests of states and cities several informative appendices were added or expanded to support jurisdictions and project teams seeking alternatives to traditional energy-cost-based compliance for an emissions reduction approach. These include optional pathways focused on source energy, carbon emissions, end-use performance factors, and net zero operation emission building outcomes, using either prescriptive (Appendix N) or performance-based approaches (Appendix M).

  • Appendix M provides a performance compliance pathway, based on Appendix G, which may be adopted by a jurisdiction or rating authority to achieve net zero operational energy emission (NZOEE) buildings. The performance pathway also includes building performance factors (BPFs) calculated on a site energy basis to ensure a minimum level of energy efficiency performance. The greenhouse gas emissions covered in Informative Appendix M include both on-site and upstream emissions associated with building energy use; they do not include emissions associated with other building use operations, such as refrigerant leakage or water use.
  • Appendix N provides a prescriptive compliance pathway that may be adopted by a jurisdiction or rating authority to achieve NZOEE buildings; it also incorporates the NZOEE performance path of Informative Appendix M. The prescriptive option is limited to buildings with common loads and standard, simple HVAC systems; compliance can be shown through emissions calculations or by meeting minimum renewable energy requirements. The greenhouse gas emissions covered in Informative Appendix N include both on-site and upstream emissions associated with building energy use; they do not include emissions associated with other building use operations, such as refrigerant leakage or water use.
  • Informative Appendix O provides an optional approach for implementing Appendix G that is particularly useful for projects with a typical load profile such as data centers. This appendix provides end-use-specific performance factors (EUPFs) that can be used in place of a single BPF, allowing compliance targets to reflect the distribution of energy end uses in each project. While Appendix G continues to use energy cost as its compliance metric, the end-use performance factors are also provided for site energy, source energy, cost, and carbon emissions for jurisdictions that elect to apply them.

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Buy Standard 90.1 

Buy the latest edition of 90.1: I-P Edition | SI Edition

More Ways to Buy

ASHRAE now offers publications in multiple formats so you can select the option that's best for you.

  • Printed Edition + PDF bundle—Purchase Standard 90.1 in print format and get electronic online access in PDF format, in addition to your print copy, for one low price.
  • Multi-user PDF—Purchase access to Standard 90.1 for use in your company for up to nine users.
  • Digital Collections—Need company-wide access? Digital Collections provide web-based, enterprise access to ASHRAE and other-industry publications for your information needs.

Preview Older Editions of Standard 90.1

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Standard 90.1 Training

ASHRAE continually offers several training options related to 90.1, including instructor-led training, on-demand eLearning, self-directed training, and training in conjunction with ASHRAE and other industry events. See the various options and sign up by viewing our Professional Development page.

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Standard 90.1 Resources

User's Manuals

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90.1 ECB App

A tool for modeling compliance with ASHRAE Standard 90.1-2010

A free web application from ASHRAE automates the calculations needed to show a building project’s compliance with ASHRAE/IES Standard 90.1-2010 using the Energy Cost Budget (ECB) Method described in the standard. The calculations are based on the ECB Method Compliance Forms found in the 90.1-2010 User's Manual.

Input your project parameters and then calculate your proposed design’s projected performance and compliance—no need to build your own spreadsheet. Output your results in Microsoft® Excel® for your clients and project records.

The app is accessible from your desktop, tablet, or other device anywhere. Set up an account  and store your project information in one place for easy reference and comparison.

Visit 901ECB.ashrae.org to register and get started.

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