CODES & STANDARDS | National energy standard influences commercial building code

July 28, 2023
CRAIG DILOUIE summarizes modifications in the 2019 90.1 energy reference standard that states will likely use for commercial energy code adoption, and compares alternatives to the standard.

The United States does not have a national commercial building energy code. Instead, the country leaves code adoption to individual states. However, it does have a national energy reference standard that is influential in code adoption. 

As required by the Energy Conservation and Production Act, the U.S. Department of Energy (DOE) issues determinations on whether the latest version of ANSI/ASHRAE/IES 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, will improve energy efficiency over the previous version. States then have two years to adopt this version or an equivalent. Those that comply are eligible for funding to assist in code implementation.

On July 28, the 2019 version of 90.1 will go into effect as the new national energy reference standard. What does that mean, what is different in the 2019 version, and what are popular alternatives to this standard?

Circle of influence

Commercial building energy codes regulate the design efficiency of new buildings and renovations. As such, they influence product development and adoption of energy-efficient lighting technologies. The lighting sections within the codes typically prescribe maximum power allowances and mandate various measures, notably energy-saving lighting controls.

States may write their own codes as in the case of California (Title 24, Part 6) or adopt a model such as 90.1 or the International Energy Conservation Code (IECC). The latter two are updated every three years. Some states — such as Colorado with its home rule constitution — do not have a statewide code, though jurisdictions within these states may adopt them. As a result, the U.S. has become a patchwork of different codes that update to new versions over time, which can make compliance complex.

While IECC is used by a majority of states, 90.1 has its own special significance because the DOE recognizes it as the national energy reference standard. As such, it is influential in IECC’s development as the two models constantly seek alignment. Furthermore, 90.1 serves as a standard for federal construction and green-building initiatives such as LEED. The IECC also recognizes 90.1 as an alternative compliance standard.

As of March 2023, around six states were compliant with the DOE requirement by having an energy code at least as stringent as 90.1-2019. However, more than 15 states eventually complied with the previous ruling recognizing the 2016 version of 90.1 as the national energy reference standard, suggesting that compliance with the current ruling will reach a significant level over time. Among the states taking longer, some may jump over 90.1-2019 and IECC 2021 to adopt 90.1-2022 or the upcoming IECC 2024.

Updates and notes to 90.1

For lighting, compared to the 2016 version of 90.1, the 2019 version modifies interior lighting power allowances and some mandatory control requirements, and it provides a new, simplified compliance method for office, school, and retail buildings. I cover several significant changes here, though not all changes. Details,  such as exceptions, are not covered; rather, this information is for general educational purposes and subject to final interpretation by the authority having jurisdiction (AHJ).

Lighting power: Standard 90.1 prescribes maximum interior lighting power allowances using the Building Area Method (whole building) or Space by Space Method (per space). The 2019 version modified these allowances based on modeling using updated technology and IES light level recommendations.

A few building types, including libraries and parking garages, received a bump up in power allowances, while the rest saw reductions ranging from modest to major. Among common market segments, office buildings and retail saw a roughly 20% reduction, while schools and universities, hospitals, and manufacturing buildings saw a roughly 10% reduction. This reflects a general trend among codes and standards toward lower power allowances, which also reflects the growing maturity of LED lighting.

New compliance path: The 2019 version offers a new simplified Building Area Method for buildings in which at least 80% of floor space is used for office, retail, or school purposes, under certain conditions. Tables 9.3.1-1, 9.3.1-2, and 9.3.1-3 in the standard (not shown) list lighting applications along with power allowances and control requirements. This is a significant change in that it represents an effort to simplify the standard to facilitate compliance.

Controls: The 90.1 standard mandates a broad range of automatic lighting controls, which is part of an ongoing trend toward more detailed control strategies in recognition of viable control technology and significant energy savings gainable beyond power allowances. Basically, with some exceptions, all lighting must be automatically turned off or reduced when it’s not needed, with supplementary manual control. The 2019 version updated requirements for parking garages, revised daylight-responsive control requirements, and added a definition of continuous dimming based on NEMA LSD-64-2014.

Parking garages have particular control requirements. In the 2019 version, lighting power to luminaires must be reduced by at least 50% when no occupant activity is detected for 10 minutes. The standard also addresses parking garage transition lighting.

In daylight-responsive lighting control, the photocontrol in daylight areas must reduce lighting power via continuous dimming in response to daylight by at least 80% (including off). If another partial-off control reduces lighting power, the daylight-responsive control can respond to daylight but may not increase power above the partial-off level.

IECC 2021 distinctions

Published by the International Code Council, the IECC is a model code available to jurisdictions to adopt as a commercial building energy code. In terms of requirements, the 2021 version is considered equivalent to 90.1-2019.

Compared to the 2018 version, the 2021 version reduces lighting power allowances while expanding mandatory control requirements, notably the addition of daylight-responsive control to secondary daylight zones, and new requirements for parking garage controls. In addition, it requires more expansive automatic power receptacle control. Salient changes follow, with the same qualifiers applying to our description of 90.1 that not all details are listed here.

Lighting power: Like 90.1-2019, IECC 2021 reduces interior lighting power allowances in a significant number of building types.

Occupancy sensing: IECC 2021 added corridors to the list of spaces requiring occupancy sensor–based automatic shutoff. In corridors, the lighting must be reduced by at least 50% within 20 minutes of detecting no occupancy.

Daylight-responsive lighting controls: IECC 2021 requires that general lighting in daylight zones feature independent daylight-responsive controls. IECC defines the dimensions of these daylight zones based on whether they are sidelit (adjacent to vertical fenestration such as windows) or toplit (under fenestration such as skylights).

IECC 2021 now identifies secondary daylit zones, which potentially doubles the reach of daylight-responsive controls; and recognizes a rooftop monitor as producing sidelit illumination. The code recognizes projection factor (shading by overhanging projections) as potentially limiting the utility of implementing daylight-responsive control. Finally, daylight zones in atrium spaces must be established at the top floor surrounding the atrium and not any intermediate floors.

In all daylight-responsive control applications, the control must be automatic and provide continuous dimming to 15% of full light output or lower and capable of turning the lights off. In warehouses, open offices, and corridors where occupancy sensing produces a light-reduction effect, daylight-responsive controls may further reduce power but not raise it above the level set by the occupancy sensor.

Parking garages: Parking garage lighting must be controlled by an occupancy sensor or time-switch control. In addition, lighting power must be reduced using an occupancy sensor and with a maximum 3,600-square-foot control zone. Lighting at entrances and exits must be reduced by at least 50% between sunset and sunrise.

Power receptacle control: IECC 2021 expands automatic plug load control beyond sleeping units, which can be served by lighting controls. Specifically, at least 50% of all permanently installed 125V, 15A, and 20A receptacles installed in certain applications — including enclosed offices, workstations, and classrooms — must be controlled. At least 25% of branch circuit feeders installed for modular furniture not shown on the plans must be controlled.

The control function may be based on split-controlled receptacles (top controlled), or separate controlled receptacles must be installed within 1 foot of each uncontrolled receptacle. All controlled receptacles must be marked per NFPA 70 and uniformly distributed. The receptacles may be controlled either on a scheduled basis using a time-switch control, via an occupancy sensor with a 20-minute time delay, or via a signal from another control or alarm system.

Exterior lighting controls: Exterior lighting must be turned off when sufficient daylight is present. Building façade and landscape lighting must be automatically turned off during the night when it is no longer needed. All other exterior lighting — typically operating from dusk to dawn — must be reduced during the night based on time or occupancy.

In IECC 2021, this dusk-to-dawn lighting power must be reduced by at least 50%, not 30%, after hours. Outdoor parking lot luminaires greater than 78W and with a mounting height of 42 feet or less must be controlled with an occupancy sensor that reduces power by at least 50% with a 15-minute time delay. For such luminaires, control zoning is limited to 1500W of lighting power.

Additional energy efficiency: Buildings complying with IECC 2021 must enhance energy efficiency by installing various stretch options, such as renewable energy and recovered or renewable water heating. Two of the listed options cover lighting and controls. With the 2021 version, the table was expanded into a credit system. New buildings are required to gain 10 credits from among 15 options. Between lighting and controls, 10 credits can be gained. For lighting, this involves achieving an even lower lighting power density. For controls, it involves using a digital lighting control system with certain capabilities.

Energy codes set the standard

Commercial building energy codes define a baseline design energy efficiency for buildings. As such, they set the standard for the minimum of what is achievable with available technology.

The general trend over the past two decades has been decreased lighting power allowances and increasingly detailed lighting control strategies. The latest model codes and standards assume LED as the predominant light source and require lighting control solutions in many spaces as part of an overall goal to maximize building energy efficiency. Unfortunately, the resultant growing complexity in energy codes requires education of lighting practitioners, designers, installers, and owners.

As energy codes realize the full potential for savings, they may head in new directions. Currently, various jurisdictions are experimenting with codes that regulate energy consumption or carbon emissions in existing buildings. As these experiments develop, we may see building energy codes evolve.

For more information about 90.1-2019 and IECC 2021, consult the standard or model code. For specific interpretations, consult the AHJ.

CRAIG DILOUIE, LC, CLCP serves as education director for the Lighting Controls Association, a council of NEMA dedicated to educating the public about lighting controls.

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About the Author

Craig DiLouie

Craig DiLouie, LC, CLCP, is education director for the Lighting Controls Association, a council of the National Electrical Manufacturers Association dedicated to educating the public about lighting control technology and application. Learn more at