ASHRAE/IES 90.1-2022 Becomes New National Energy Reference Standard

In March 2024, the U.S. Department of Energy (DOE) determined that the 2022 version of ASHRAE/ANSI/IES 90.1, Energy Efficiency Standard for Buildings Except Low-Rise Residential Buildings, saves energy over the 2019 version. As such, this standard became recognized as the new national energy reference standard.

What this means: Each state must certify their state building code is as energy-efficient as this version of 90.1 or justify why they cannot comply within two years of publication of the DOE ruling in the Federal Register.

This article explains how energy code adoption works, the likelihood of adoption of the 2022 or an equivalent standard in various jurisdictions, and what’s new in the standard, focusing on lighting control requirements.

Energy codes

Commercial building energy codes regulate the designed energy efficiency of nonresidential buildings. As technological advances afforded substantial energy savings, lighting has been a favored target for energy efficiency improvement.

These codes typically include prescriptive and mandatory requirements. Prescriptive requirements focus on the lighting side, capping lighting power density (LPD, expressed as W/sq.ft.) for either buildings by building type or indoor and outdoor spaces by space type, depending on the compliance method. Lighting controls typically fall under mandatory requirements, with various control strategies and parameters required in a majority of space types.

States may write their own codes, as California does with Title 24, Part 6, or adopt a model code or standard in whole or part. Other states do not have a statewide energy code, such as Colorado with its home rule constitution, though there may be significant adoptions at the county or municipal level.

The most prevalent model codes are ASHRAE/ANSI/IES 90.1 and the International Energy Conservation Code (IECC). While a majority of codes are based on the IECC, 90.1 is recognized by the DOE as the national reference standard; 90.1 is also the basis for building rating systems such as LEED. Further, the IECC recognizes 90.1 as an alternative compliance standard. Both model codes are updated every three years.

As a result, the United States is a patchwork of code adoption, as shown in this status of code adoption map produced by the DOE (March 2024):

Since 1999, the overall trend is toward lower power allowances and more detailed control requirements to maximize energy savings. A significant driver in progressive energy efficiency has been the Energy Conservation and Production Act, which authorizes the DOE to recognize a national energy reference standard and require all states to adopt an energy code as least as energy-efficient as this standard or justify non-compliance.

Before recognition of the 2022 version, the 2019 version was recognized, with a requirement for all states to comply by July 2023. Based on historical compliance, 13 states are expected to comply with the new ruling by the deadline.

ASHRAE/ANSI/IES 90.1-2022

The 2022 version of 90.1 includes an expanded scope for building sites, a minimum prescriptive requirement for onsite renewable energy, and other major additions appearing for the first time in a U.S. model energy standard or code. For lighting, the new version adjusts power allowances, adjusts the definition of alterations, adds horticultural lighting, and updates several control requirements.

The DOE estimates that buildings meeting the updated Standard 90.1-2022, as compared to buildings meeting the 2019 edition, would result in national site energy savings of 9.8 percent, source energy savings of 9.4 percent, energy cost savings of 8.9 percent, and carbon emissions savings of 9.3 percent. When accounting for the impact of onsite renewable energy systems, the national average site energy savings estimate increases from 9.8 to 14 percent.

Let’s take a look at what’s new, focusing on salient changes while noting this information is provided for educational purposes only and does not constitute a definitive interpretation, which is up to the authority having jurisdiction. For more information, interpretations, and definitively accurate reading of the text, consult the code or the applicable AHJ.

Building sites

ANSI/ASHRAE/IES 90.1-2022 clarifies the scope of 90.1 to include the site, not just the building.

Before this change, the standard covered only systems fed by building power. As a result, exterior and parking lot lighting, if not provided through the building’s main electrical panel, were previously not within the scope of 90.1. Now it is.

Inclusion of the building site also ensures that onsite renewables can count as credits toward energy usage even if not part of the building footprint.

Lighting alterations

As 90.1 evolved, lighting retrofits have increasingly been recognized within the standard’s scope. In the 2022 version, all alterations are grouped together, including retrofits in which the original lamps and driver/ballasts are replaced with lamps and drivers/ballasts that were not components of the original luminaire. These alterations are then broken out and assigned separate requirements depending on whether the lighting is interior or exterior.

Interior: If the lighting system in the interior building spaces adds up to more than 2000W of load, the alteration must comply with 1) the lighting power allowance and 2) mandatory control requirements applicable to each altered space. If the connected lighting load is 2000W or less, the alteration must comply with 1) the standard’s lighting power allowance requirements (or result in new wattage at least 50 percent below the original wattage of each altered lighting system) while 2) needing only comply with the standard’s manual local and automatic shutoff mandatory lighting control requirements.

Exterior: For an exterior building area, if the total number of new or retrofitted luminaires is greater than 10 or where the combined length of new and retrofitted linear luminaires is greater than 20 linear feet, the alteration must comply with the standard’s lighting power allowance and mandatory control requirements. If the alteration is smaller, it must comply with lighting power allowance requirements (or result in new wattage at least 50 percent below the original wattage of the system) but only need be controlled by an Off switch.

Lighting power

The 90.1 standard limits maximum lighting power density. Unless opting to use complex building modeling, designers can choose one of two compliance paths, either the Building Area Method (single maximum power allowance in W/sq.ft. for entire building) or Space by Space Method (maximum power allowance for each type of space within building). The standard also caps exterior lighting power using a system of base allowances and tradable surfaces.

The 2022 version of 90.1 adjusted Building Area Method power allowances.

Exterior lighting power allowances are significantly reduced compared to previous versions of the standard. For interior lighting power, allowances were generally reduced or stayed the same. Also generally, when power allowances were reduced, they were not reduced as significantly as in previous versions, suggesting maturing acceptance of LED by 90.1.

Some examples of the reduction in interior lighting power allowances are shown in the table below:

 

Building type	90.1-2016	90.1-2019	90.1-2022
Office	0.79W/sq.ft.	0.64W/sq.ft.	0.62W/sq.ft.
Retail	1.06W/sq.ft.	0.84W/sq.ft.	0.78W/sq.ft.
School/University	0.81W/sq.ft.	0.72W/sq.ft.	0.70W/sq.ft.
Hospital	1.05W/sq.ft.	0.96W/sq.ft.	0.92W/sq.ft.
Manufacturing	0.90W/sq.ft.	0.82W/sq.ft.	0.82W/sq/ft.
Warehouse	0.48W/sq.ft.	0.45W/sq.ft.	0.45W/sq.ft.

Horticultural lighting

This new 90.1 lighting section addresses the distinct characteristics of horticultural lighting. Certain horticultural luminaires must achieve a minimum photosynthetic photo efficacy (PPE), a metric adopted in ANSI/ASABE S640, and be controlled by a device that automatically turns them Off at specific times.

Germicidal lighting

The 2022 version of 90.1 added power used only for a germicidal function in lamps or luminaires to the list of lighting exempted from interior power allowance calculations.

Track lighting

The 2019 version of 90.1 provided only one method for calculating the wattage of line-voltage track lighting and plug-in busway designed to allow the addition and/or relocation or lighting without system wiring alteration: the specified wattage of the system’s lighting with a minimum of 30W/linear foot. The 2022 version reduced the 30W/linear foot to 10W/linear foot in recognition of the predominance of higher-efficiency LED technology.

Decorative and retail power allowances

When using the Space-by-Space Method to comply with maximum allowed lighting power, an increase is allowed in 90.1 for specific purposes such as decoration (decorative lighting or to highlight art or exhibits that are not exempted by the standard) and supporting retail sales.

The 2022 version of 90.1 decreased the additional interior lighting power allowance for decorative lighting from 0.75W/sq.ft. to 0.70W/sq.ft. and also reduced the retail sales area additional power allowances. Additionally, 90.1-2022 created a new power allowance of 0.50W/sq.ft. for interior lighting used for videoconferencing.

Lighting controls

ASHRAE/ANSI/IES 90.1-2022 updated the lighting control requirements with several significant changes and additions.

Occupancy sensing in open offices: Previously, occupancy sensors were required as the automatic shutoff strategy in various spaces, typically smaller, enclosed spaces such as offices smaller than 300 sq.ft.. In the 2022 revision, larger offices are included, aligning 90.1 with IECC 2021 and the latest Title 24, Part 6 energy code in California.

If the office is 300 sq.ft. or larger, such as open offices, occupancy sensors are required to provide automatic shutoff within 20 minutes of the area becoming unoccupied. The control zone for each sensor is limited to 600 sq.ft.

While the 90.1-2022 standard allows up to 50 percent of the general lighting power to automatically turn On, all lighting in occupied zones is allowed to turn On to full power. If only some of the control zones in the office are occupied, the general lighting in the unoccupied zones is allowed to automatically turn On to up to 20 percent of full power. This ensures that if, for example, a single zone is occupied, the surrounding zones will be dimmed but not turn completely Off.

New threshold for daylight-response controls: The 90.1 standard requires that general lighting in daylight areas include daylight-responsive controls that independently control the lighting, with exceptions. IECC defines the dimensions of these daylight areas based on whether they are sidelit (adjacent to vertical fenestration such as windows) or toplit (under fenestration such as skylights), with sidelit areas divided into primary (directly adjacent to fenestration) and secondary (directly adjacent to primary) areas.

The 90.1 standard indicates a wattage threshold at which automatic daylight-responsive lighting controls are needed to control general lighting in daylight areas. In the 2022 version, if the total wattage of general lighting either entirely or partially in the primary sidelit area is 75W or greater, daylight-responsive control is required. This threshold was reduced from 150W in the previous version of 90.1.

Additionally, if the total wattage of general lighting either entirely or partially in the primary and secondary sidelit areas is 150W or greater, daylight-responsive control is required in both areas, with each area being independently controlled. This was reduced from 300W in the previous version of 90.1.

For toplit areas, if the total wattage of all general lighting either entirely or partially in a daylight area under skylights and roof monitors is 75W or greater, daylight-responsive control is required for the area. This was reduced from 150W in the previous version of 90.1.

In all of the above cases, the daylight-responsive control must reduce lighting power in response to daylight using continuous dimming to 20 percent (or less) plus Off. Note that general lighting in overlapping sidelit and toplit daylight areas must be controlled together.

Exterior lighting controls: Standard 90.1-2022 now requires that all exterior lighting be furnished with an Off control. All exterior lighting must be capable of being reduced by at least 50 percent in response to either a schedule or occupancy sensing. In the case of occupancy sensing, light reduction must occur within 15 minutes of vacancy and a single control zone may include no more than 1500W of controlled lighting.

Guestroom lighting controls: Both the 2019 and 2022 versions of 90.1 require automatic shutoff control of lighting and all switched power receptacles in guestrooms and suites in hotels, motels, boarding houses, and similar buildings. Specifically, lighting and switched receptacles in each enclosed space must be turned Off within 20 minutes after it becomes unoccupied. For bathrooms, shutoff must occur within 30 minutes, with up to 5W of night lighting exempted.

In the 2019 and other previous versions of 90.1, rooms where lighting and switched receptacles controlled using a captive card key system were exempt. The 2022 version eliminated this exemption, recognizing card key control as often bypassed and being otherwise largely obsolete.

Dwelling unit controls: For dwelling units such as living spaces in 4+ story multifamily buildings (not including hotel/motel guestrooms), the 2019 version of 90.1 required that at least 75 percent of permanently installed luminaires provide a light source efficacy of at least 55 lumens/W or a total luminaire efficacy of at least 45 lumens/W. A significant exemption is for lighting controlled by dimmers or turned Off automatically via occupancy sensing.

The 2022 version of 90.1 increased minimum source efficacy to 75 lumens/W and luminaire efficacy to 50 lumens/W and made the previous controls exemption a requirement. In dwelling units, at least 50 percent of permanently installed luminaires must be controlled by dimmers or automatically turn Off within 20 minutes of vacancy.

Additionally, permanently installed exterior luminaires dedicated to a dwelling unit must be provided with manual control while also automatically shutting Off based on schedule, occupancy (within 15 minutes), or daylight. An exemption is when the total rated luminaire wattage of these luminaires is no greater than 8W.

90.1 decoded

Overall, ASHRAE/ANSI/IES 90.1-2022 is modestly progressive on interior lighting power allowances and control requirements, with several significant changes and additions adapting 90.1 to current technology and conditions. While it may be some time before this version of the standard is widely adopted, it may be useful to begin familiarizing oneself with its changes now.

For more information, consult ASHRAE/ANSI/IES 90.1-2022, available at the ASHRAE bookstore here.