Energy codes and building performance standards in the US

Energy codes set the minimum energy performance for new buildings and major renovations, and building performance standards increasingly set limits for existing buildings. Together they are the main regulatory driver of operational energy and carbon. CON-140 explained how the International Code Council's model codes are developed and adopted by states and cities; this lesson looks at the energy codes and standards themselves, the stretch codes some jurisdictions use to go further, and the benchmarking and performance rules that apply once a building is occupied. Codes change frequently and adoption varies by state and city, so treat the details here as a map dated 2026 and always check the edition in force where you build.

How energy codes work

Energy codes usually offer two or three compliance paths. A prescriptive path sets minimum values for each component, such as maximum U-values for walls, roofs and windows, minimum equipment efficiencies, lighting power limits and controls. A trade-off path lets a better component offset a weaker one within limits. A performance path compares an energy model of the proposed building with a model of a reference building that just meets the prescriptive requirements, and the proposed building must use no more energy (or emit no more, in codes with emissions metrics) than the reference. Performance paths give designers flexibility but depend on modeling skill and honest inputs, and most also have mandatory requirements, such as airtightness and controls, that apply whatever the path.

For builders, codes create two practical responsibilities. First, what is built must match what was approved: a substituted window, a missing thermal break or a different mechanical unit can make the building non-compliant even if it was compliant on paper. Second, more codes now require tests and documentation during construction, such as airtightness tests, commissioning reports and as-built energy model updates, which must be scheduled and paid for.

The model energy codes

The two main model energy codes in the United States are the International Energy Conservation Code (IECC), published by the International Code Council every three years, and ANSI/ASHRAE/IES Standard 90.1, which the IECC allows as an alternative for commercial buildings and which is the federal reference standard for commercial energy codes. The IECC has separate residential and commercial provisions; mid-rise apartment buildings of four stories or more fall under the commercial provisions and 90.1. The 2021 and 2024 IECC and 90.1-2022 are the most recent editions, and the 2024 IECC added requirements for additional efficiency credits, electric-ready and renewable-ready provisions, some of them in appendices that jurisdictions can choose to adopt.

State adoption is uneven. Some states adopt each new IECC edition promptly, others lag by one or more editions, some have no statewide code and leave adoption to local governments, and some, such as California with its Title 24 Part 6 standards and Washington and Oregon with their own state energy codes, write their own codes that often exceed the IECC. Federal law requires the Department of Energy to determine whether each new edition saves energy and requires states to certify that their commercial codes meet the latest 90.1 edition, but enforcement of that requirement is limited. Federal funding to help states adopt the latest codes was part of the 2022 Inflation Reduction Act, and its status has changed with later federal budget decisions, so check before relying on it.

Stretch codes and state standards

Many states and cities go beyond the base code. Stretch codes are optional, more stringent codes that local governments can adopt; Massachusetts, for example, has a stretch energy code and a municipal opt-in specialized code with net zero provisions. New York's state energy code and New York City's local energy code exceed the IECC, and Washington state's energy code is among the most stringent and favors heat pumps for space and water heating. Some cities tried to ban gas connections in new buildings; a 2023 federal appeals court decision against Berkeley's ban led many cities to shift to other approaches, such as all-electric preferences in energy codes or emissions limits, and the legal picture continues to evolve.

# Local Law 97-style emissions and penalties (coefficients and R-2 limits for 2024-2029 and 2030-2034)
ELEC, GAS = 0.000288962, 0.00005311     # t CO2e per kWh and per kBtu (2024-2029 coefficients)
LIMITS = {'2024-2029': 0.00675, '2030-2034': 0.00407}   # t CO2e per ft2 per year, multifamily (R-2)
PENALTY = 268                            # dollars per t CO2e over the limit
buildings = {   # name: (gross ft2, electricity kWh/yr, gas kBtu/yr)
    'Cedar Row, gas design':        (90400, 462000, 2237000),
    'Cedar Row, heat pump design':  (90400, 678000, 0),
    '1970s apartment building':     (120000, 1600000, 9500000),
}
for name, (ft2, kwh, kbtu) in buildings.items():
    e = kwh * ELEC + kbtu * GAS
    out = [f"{name:28s} {e:5.0f} t/yr"]
    for period, lim in LIMITS.items():
        over = max(0.0, e - lim * ft2)
        out.append(f"{period}: limit {lim * ft2:4.0f} t, penalty ${over * PENALTY:8,.0f}")
    print(' | '.join(out))

Cedar Row, gas design          252 t/yr | 2024-2029: limit  610 t, penalty $       0 | 2030-2034: limit  368 t, penalty $       0
Cedar Row, heat pump design    196 t/yr | 2024-2029: limit  610 t, penalty $       0 | 2030-2034: limit  368 t, penalty $       0
1970s apartment building       967 t/yr | 2024-2029: limit  810 t, penalty $  42,045 | 2030-2034: limit  488 t, penalty $ 128,234

Both Cedar Row designs would comply easily with New York City's Local Law 97 limits for 2024–2029 and 2030–2034 if the building were in New York, because they are new and efficient. The 1970s building, by contrast, would pay about $42,000 a year in penalties during the first compliance period and about $128,000 a year in the second, which is why owners of older buildings are planning heat pump retrofits, envelope upgrades and controls improvements. For contractors, building performance standards are creating a large retrofit market in existing buildings.

Building performance standards

Building performance standards (BPS) set limits on energy use or emissions for existing buildings, usually large ones, with penalties for non-compliance. New York City's Local Law 97 covers most buildings over 25,000 square feet, sets emissions limits by occupancy type that tighten in 2030 and again toward net zero by 2050, and charges $268 for each metric ton of CO2e over the limit. Boston's BERDO 2.0, Washington state's Clean Buildings Performance Standard (based on energy use intensity targets, with the largest buildings due to comply from 2026), Denver's Energize Denver, and statewide standards in Colorado and Maryland follow similar principles. Most build on benchmarking ordinances that require annual reporting through ENERGY STAR Portfolio Manager. Legal challenges and amendments are common: an appeals court revived a preemption challenge to Local Law 97, but the law remained in full effect in 2026 while the litigation continued.

ENERGY STAR Portfolio Manager, the free tool most benchmarking laws rely on, faced proposed elimination in 2025. Congress funded ENERGY STAR for fiscal year 2026, and in March 2026 the Environmental Protection Agency and the Department of Energy agreed to make DOE the program's lead agency, with systems and partnerships moving over during 2026. Builders and owners should watch for changes to tools and scores, but benchmarking requirements in state and local law continue regardless.

Federal incentives and their end

For several years, two federal tax incentives shaped green building economics. Section 179D provided a deduction for energy-efficient commercial and large multifamily buildings, and Section 45L provided a credit to builders of energy-efficient homes, including multifamily units, both expanded by the Inflation Reduction Act in 2022. The One Big Beautiful Bill Act of 2025 ended them early: 179D is not available for property whose construction begins after June 30, 2026, and 45L is not available for homes acquired after June 30, 2026. Projects already under construction or completed before those dates may still qualify if they meet the requirements, including prevailing wage rules for the larger amounts. The federal Buy Clean program for low-carbon materials was also ended in 2025 (Lesson 12). For Cedar Row, which starts construction after mid-2026, neither incentive is available, so the business case must rest on operating savings, local incentives, utility programs and the owner's own goals.

Policy views differ sharply on these instruments. Supporters of stringent codes and performance standards argue that buildings last for decades, that efficiency is cheapest to build in at the start, and that markets underinvest because of split incentives between owners and tenants. Critics argue that each increment adds to construction and housing costs, that rules written for large cities may not suit small towns or cold rural regions, and that incentives and information may achieve similar results with less burden. Builders should be able to explain the costs and benefits of each option accurately to clients, whatever their own views.

What codes mean on site

Code compliance is increasingly verified by testing and documentation rather than drawings alone. A builder should expect to provide some or all of the following, and to plan time and money for them.