ASHRAE/IES 90.1-2022 DECODED

By Craig DiLouie, LC, CLCP

The American Society of Heating, Refrigerating, and AirConditioning Engineers (ASHRAE) and the Illuminating Engineering Society (IES) recently published ANSI/ASHRAE/IES Standard 90.1-2022, Energy Efficiency Standard for Buildings Except Low-Rise Residential Buildings

This edition 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.

Commercial building energy codes regulate the designed energy efficiency of nonresidential buildings. A majority of states rely on model energy codes such as 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 U.S. Department of Energy as the national reference code (currently the 2019 version, with all states required to adopt a code at least stringent as this version by July 2023); it 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.

For lighting, typically, energy codes impose a mix of prescriptive and mandatory requirements, with mandatory requirements focused on lighting controls. Since 1999, the overall trend is toward lower power allowances and more detailed control requirements to maximize energy savings. The 2022 version of 90.1 is no exception, with changes focused on tightening interior power allowances—based almost entirely on LED technology— while tweaking requirements for lighting controls.

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 and interpretations, consult the code or the applicable AHJ.

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.

Including sites also confirms that onsite renewables can count as credits toward energy usage across the building even if not part of the building footprint.

As 90.1 evolved, lighting retrofits have increasingly become recognized as within the standard’s scope. In the new 2022 version, all alterations are lumped 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 the standard’s lighting power allowance and mandatory control requirements that are applicable to each altered space. If the connected lighting load is 2000W or smaller, the alteration must comply with 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) and then comply with only 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) and then be controlled by at least an Off switch.

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.

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.

Here are some examples:

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

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 being subject to interior power allowances.

When 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 2019 version of 90.1 offered one option – 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 higher-efficiency LED technology being predominant.

When using the Space-by-Space Method to comply with maximum allowed lighting power, an increase is allowed 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. while also reducing the retail sales area additional power allowances. Additionally, 90.1-2022 created a new additional power allowance of 0.50W/ sq.ft. for interior lighting used for videoconferencing.

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

Occupancy sensing in open offices: Occupancy sensors are required as the automatic shutoff strategy in various spaces, typically smaller, enclosed spaces such as offices smaller than 300 sq.ft.. Now 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 being unoccupied. The control zone for each sensor is limited to 600 sq.ft.

While the 90.1-2022 standard allows up to 50% of the general lighting power to automatically turn On, here 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% of full power. This ensures that if, say, a single zone is occupied, it is surrounded by dim but not dark zones.

New threshold for daylight-response controls: Standard 90.1 requires that general lighting in daylight areas feature daylightresponsive 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 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 will reduce lighting power in response to daylight by 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 of full power in response to both a schedule and 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 being exempt.

In the 2019 and other previous versions of 90.1, rooms where lighting and switched receptacles were to be 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 feature 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 automatically turned Off via occupancy sensing.

The 2022 version of 90.1 increased minimum source efficacy to 75 lumens/W and luminaire efficacy to 50 lumens/W while making 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.

Overall, ASHRAE/ANSI/IES 90.1-2022 is modestly progressive on interior lighting power allowances and control requirements, though with several significant tweaks and additions adapting 90.1 to current technology and conditions. While it may be some time before this version of the standard sees adoption, 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 ■