ANSI/ASHRAE/IES 100-2024
Energy and Emissions Building Performance Standard for Existing Buildings
- Standard No.
- ANSI/ASHRAE/IES 100-2024
- Release Date
- 2024
- Published By
- American National Standards Institute （ANSI) US / ANSI
- Latest
- ANSI/ASHRAE/IES 100-2024
- Introduction
Standard Overview and Development Background
ANSI/ASHRAE/IES Standard 100-2024 (hereinafter referred to as "Standard 100") is an energy and emission performance standard for existing buildings, developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) in collaboration with the Illuminating Engineering Society (IES). This standard aims to help existing buildings reduce energy consumption and carbon emissions and address climate change challenges through mandatory requirements. Statistics show that there are approximately 5.9 million existing commercial buildings and 124 million residential buildings in the United States, accounting for 40% of total national energy consumption, 70% of electricity consumption, and 40% of carbon dioxide emissions. Among existing buildings, approximately 90% will still exist in 10 years, 75%-80% will exist in 2030, and at least 50% will exist in 2050. Therefore, improving the performance of existing buildings is key to emission reduction.
Standard 100 was first published in 2018. The 2024 version underwent major updates, including: renaming to "Energy and Emission Building Performance Standard," adding greenhouse gas intensity (GHGI) targets, updating energy use intensity (EUI) targets (based on 2012 CBECS and 2015 RECS data), adding regional energy conversion factors, and providing an optimized emission reduction measure package for buildings without targets (based on a ten-year simple payback period with carbon costs). The standard is written in mandatory, enforceable language, suitable for inclusion in building codes, and has been adopted by multiple jurisdictions in the United States.
Core Requirements and Framework
Standard 100 requires building owners to develop an energy and emission management plan (Chapter 5), implement an operations and maintenance plan (Chapter 6), and achieve compliance based on EUIt and GHGIt targets determined in Tables 7-2 through 7-6. Buildings must meet both on-site or source EUI targets and GHGI targets. If targets are not met, an energy audit and decarbonization assessment (Chapter 8) must be conducted, energy efficiency measures (EEMs) and emission reduction measures (ERMs) must be implemented, and verification must be completed within 15 months.
Dimension Standard 100-2024 Standard 100-2018 Metrics EUI + GHGI (dual targets) EUI only Data Basis 2012 CBECS + 2015 RECS 2003 CBECS + 2005 RECS Climate Zones 20 (newly added 0A, 0B, 1B) 17 Building Types 55 (newly added bars/lounges, courthouses) 53 Compliance Path Compliance / Energy Audit + Optimized Measure Package Compliance / Energy Audit + Economically Feasible Measures Carbon Cost Included in ten-year payback calculation Not specified Key Definitions: HVAC systems, lighting systems, building envelopes, etc., are all within the scope of operations and maintenance requirements. The standard requires all replacement equipment to meet the highest efficiency standards, and lighting power density must not increase (unless illuminance is below IES recommended values).
Technical Evolution and Implementation Recommendations
Standard 100 has shifted from focusing solely on energy consumption to balancing energy consumption and carbon emissions, reflecting the industry's response to climate change. Its technical evolution includes: converting from source energy consumption to regionalized emission factors; introducing the concept of carbon costs to make the economic assessment of emission reduction measures more comprehensive; and using optimized measure packages that consider interaction effects through iterative calculations to ensure maximum emission reduction.
Implementation Recommendations: 1) Building management should prioritize establishing an energy and emission accounting system to record 12 months of continuous data; 2) Develop a capital management plan to gradually phase out fossil fuel equipment (except for backup equipment); 3) For buildings without targets, use the optimized measure package to achieve at least 75% of estimated energy savings and emission reductions; 4) Utilize regional source energy conversion factors and GHG emission factors (such as Tables 5-3 and 5-4) to improve accuracy.
Case Study: Office Building Compliance Path
An office building (Activity Type 1: Administrative/Professional Office) located in Climate Zone 4A with an area of 10,000 m². According to Table 7-2b, the on-site EUI target is 200 MJ/m²·year; according to Table 7-4b, the GHGI target is 12 kg CO₂e/m²·year. If the measured EUI is 250 and GHGI is 15, the targets are not met. An energy audit is required to identify EEMs such as upgrading LED lighting, optimizing VAV system controls, and adding building automation systems. After 12 months of verification following implementation, if EUI drops to 180 and GHGI drops to 10, compliance is achieved.
Standard 100 provides a progressive improvement framework for existing buildings, helping to achieve long-term carbon neutrality goals. Jurisdictions can adjust targets based on Appendix J (Guidelines for Developing Local Targets) to adapt to regional characteristics.
ANSI/ASHRAE/IES 100-2024 history
- 2024 ANSI/ASHRAE/IES 100-2024 Energy and Emissions Building Performance Standard for Existing Buildings
- 2018 ANSI/ASHRAE/IES 100-2018 Energy efficiency in existing buildings
