Deep Dive Into the Lighting Control Requirements of the 2024 IECC

Commercial building energy codes prescribe the design energy efficiency of new buildings and alterations. For lighting, these codes typically prescribe maximum lighting power allowances by building or space type. They also mandate detailed lighting control strategies that reduce or turn Off lighting when it isn’t needed, while providing manual control to occupants.

The United States does not have a national energy code. States may write their own code or adopt a standard or model such as ANSI/ASHRAE/IES 90.1 or the International Energy Conservation Code (IECC), which are periodically updated. Some states do not have a statewide code, though adoption may occur in various jurisdictions within their borders. The result is designers may encounter multiple codes and versions of these codes.

Published by the International Code Council (ICC), the IECC has been adopted by most states as a commercial energy code, residential energy code, or both. Updated every three years since 2000, it applies to various energy-using systems installed in new construction, additions, and alterations, including electric lighting.

Based on a new NEMA Academy course, this article provides general knowledge about the commercial building lighting control requirements in the 2024 revision of the IECC (as initially published, without addenda). For complete information—such as details and exceptions to various requirements—consult the code. For definitive interpretations, consult the authority having jurisdiction (AHJ).

Energy codes

While the United States does not have a national commercial building energy code, the Department of Energy (DOE) recognizes ANSI/ASHRAE/IES 90.1 as the national energy reference standard to support energy savings. In March 2024, the DOE determined the 2022 revision saves energy compared to the 2019 version, which subsequently required all states to adopt it or an equivalent by 2026 in order to receive enforcement funding, or, alternately, justify why they cannot comply.

A majority of states in the U.S. have adopted versions of the IECC, though the IECC recognizes 90.1 as an alternative compliance path. Below, we see commercial building energy efficiency adoption in the United States as of September 2024, based on analysis by the DOE, which established categories of energy efficiency based on different revisions of 90.1 or equivalence to these versions (including addenda). Note that as the IECC typically lags 90.1 in terms of alignment, the subsequent version of IECC is typically considered equivalent to a version of 90.1 (e.g., 2024 IECC being equivalent to 90.1-2022). While the map indicates a significant lag in complying with the DOE rulings, steady progress has been made to adopt more stringent codes and energy efficiency.

As code adoption varies from state to state and even among jurisdictions within states, the designer should confirm what code and version is in effect at the start of the project.

 

2024 IECC requirements for lighting controls

The 2024 IECC provides both a prescriptive (set of design goals and limitations) and performance-based (involving building modeling using software) compliance path. The prescriptive path features mandatory lighting control provisions in nearly all new construction projects as well as certain alterations, both interior and exterior (Section C503.5).

The 2024 IECC conceptually aims to minimize energy consumption by automatically reducing or turning Off lighting when it is not being used based on three inputs: occupancy, a timed event, or ambient light level. Required lighting controls include automatic shutoff, light reduction, and daylight-responsive controls. Additionally, various manual controls are required for occupant convenience and additional energy savings, and zoning restrictions ensure independent control of lighting where needed. Various exemptions apply, which are detailed in the code.

With the 2024 revision, the IECC features these notable changes:

• reductions in interior and exterior lighting power allowances;
• changes to alteration thresholds for code applicability;
• removal of the LLLC-based lighting controls formal compliance path;
• addition of a continuous dimming requirement for light reduction controls;
• changes to the enhanced energy efficiency requirements, including elimination of the digital controls option and addition of a demand-responsive controls option; and
• a requirement for functional testing of automatic receptacle controls and, if implemented in the project as enhanced energy efficiency options, high-end trim and demand-responsive lighting controls.

The following sections discuss the provisions of the 2024 revision of the IECC in greater detail. Specific sections in the code are reference for convenience.

Lighting control compliance paths

Starting with the 2018 revision, the IECC offered two paths for mandatory interior lighting controls compliance: 1) a discrete approach with remote-mounted devices that satisfies all the requirements, and 2) a nominally simpler option involving installation of luminaire-level lighting controls (LLLC) along with additional remote devices as needed.

This provision has been eliminated in the 2024 IECC, returning LLLC to being a compliance option rather than a parallel formal compliance path. This returns the code to one set of requirements, which can be satisfied with whatever solution the designer feels is optimal.

Manual control (Section C405.2)

In a majority of interior spaces, occupants are to be given the means of controlling the general lighting via manual control. This may be a discrete device (C405.2.6) or be incorporated with or as an integral part of an occupant sensor (C405.2.1.1). Manual controls must be placed so they are readily accessible to occupants. The controlled lighting must be visible to the user or, in the case of remote control, the controls must identify the area served by the manual control as well as indicate the status of the lights.

 

An occupant sensor may be full-automatic-On in some applications. In the majority of applications, however, it must be partial-On to 50 percent of power or manual-On. If the occupant sensor is partial-On, the manual control allows the lights to be raised to full or turned Off. If the occupant sensor is manual On, the manual control allows the lights to be turned On and Off.

In areas where occupant sensors are not required, a time-switch control may be used (C405.2.2). This approach must incorporate an override manual control device that enables the lighting in a maximum 5,000-sq.-ft. area to remain On for up to two hours. In the case of specific large applications such as mall concourses and sports arenas, a captive key device may be used as the override method, with the control zone configurable up to 20,000 sq.ft.

Dimming (Section C405.2.3)

Previously titled “light reduction controls,” this section has been significantly revised in the 2024 IECC. Bilevel switching has been eliminated as an option. Continuous dimming controls for general lighting in a list of spaces from classrooms to lobbies to offices (with an exception for lighting controlled by special application controls) is now required.

Dimming controls must be provided with manual control unless high-end trim lighting control is being implemented. The lights must be continuously dimmable from full output to 10 percent of full power or lower, plus Off.

Interior automatic lighting shutoff controls

Automatic shutoff controls automatically turn Off or reduce lighting when an area is vacated, based on either occupancy or schedule. The 2024 IECC requires that interior lighting be equipped with such controls. Acceptable methods include occupant-sensing or time-switch controls.

Occupant sensor controls (Section C405.2.1)

Occupant sensor controls are devices that automatically turn Off lighting when an area is unoccupied. This method may be used to comply with the 2024 IECC’s lighting shutoff requirements. Occupant sensors are specifically required as the automatic shutoff method in a wide range of spaces: classrooms, conference rooms, offices, warehouse storage areas, and more. In the 2024 IECC, data center computer rooms, medical supply and telemedicine rooms in healthcare facilities, and laundry/washing areas were added to this list.

The occupant sensor must be able to turn the lights Off within 20 minutes after the space is vacated. Though the sensor may automatically turn lighting full-On where manual operation would pose a safety or security risk or in spaces permitted by code, generally, the occupant sensor controls must either turn lighting On by manual-On or auto-partial-On to no more than 50 percent of lighting power. As stated previously, a manual control is also required so occupants can turn the lighting Off when not needed.

Occupant sensors in warehouse storage areas (Section C405.2.1.2)

Warehouse aisles are typically intermittently occupied but may need to stay On during building operating hours for safety and security. In these spaces, the lighting in aisles must be controlled independently via an occupant sensor that reduces lighting power to at least 50 percent within 20 minutes of vacancy. This allows a lower level of illumination when rack aisles are not occupied. A manual control must be provided for occupants to turn the lights On and Off. A means of full automatic lighting shutoff must still be provided.

Occupant sensors in open-plan offices (C405.2.1.3)

Starting with the 2021 revision, the IECC requires occupant sensors in offices, with special additional requirements for implementation in open-plan offices 300 sq.ft. and larger. In this application, the general lighting must be controlled by sensors with control zones limited to 600 sq.ft.

When a sensor in a control zone detects occupancy, it may turn the lights On to full. When this happens, the lights in unoccupied zones in the open office may stay Off or turn On to no more than 20 percent full power.

Within 20 minutes of a control zone being vacated, the lights must turn Off or uniformly reduce to no more than 20 percent full power. When all occupants have vacated all zones, the control system or a time-switch must turn all general lighting Off.

Occupant sensors in corridors (C405.2.1.4)

In corridors with a light level of two footcandles or more at their darkest point on the floor, the 2024 IECC requires occupant sensors to monitor for occupancy and uniformly reduce lighting power to at least 50 percent full power within 20 minutes of vacancy. This measure provides energy savings while ensuring the lights remain On for safety and security.

Automatic time-switch control (C405.2.2)

Where occupant sensors are not specifically required, automatic time-switch controls may be used to comply with the 2024 IECC’s shutoff requirements, unless specifically exempted. These controls employ a schedule, typically programmed into a microprocessor, to signal lighting to turn Off at designated times. Time-switch controls are well-suited to spaces that are rarely unoccupied during predictable operating hours.

Time-switch controls must be programmed to automatically turn the lights Off when they are not needed, with the ability to accommodate individual scheduling for each day of the week in addition to holiday shutoff. For spaces where schedules aren’t available, the 2024 revision of the IECC requires the control system be programmed to a schedule that turns the lights Off at least 12 hours per day.

Additionally, the time-switch control must provide backup capability in the event of power interruption and a manual switch override for occupants.

Daylight-responsive controls (C405.2.4)

Daylight-responsive lighting controls are required for areas receiving ample and consistent daylight. These areas are defined as primary sidelit (adjacent to vertical fenestration such as windows), secondary sidelit (adjacent to primary daylight zones), and toplit (under toplighting such as skylights) daylight zones.

The first step for compliance is to identify 1) primary, secondary, and toplit daylight zones in each interior space and their dimensions, 2) the total general lighting wattage in each zone, and 3) whether the space or area is exempt.

If the space has primary sidelit and/or toplit daylight zones containing more than 75W of general lighting, daylight-responsive control is required. (This wattage threshold was reduced in the 2024 IECC.) If the total wattage of general lighting in primary and secondary sidelit daylight zones combined is more than 150W, again, control is required. Daylight zones in multi-floor atrium areas must be established at the top floor surrounding the atrium and bottom floor, but not any intermediate floors.

The IECC recognizes projection factor (shading by overhanging projections) as potentially limiting the utility of daylight-responsive control.

The 2024 IECC requires independent automatic daylighting controls in primary and secondary sidelit and skylit daylight zones.

The lighting in sidelit and toplit zones must be controlled independently, as must lighting in primary and secondary sidelit zones. In the 2024 revision of the IECC, the calculated exemption to daylight-responsive controls in trade for reducing the lighting power allowance was removed, and an exemption has been added for enclosed office spaces smaller than 250 sq.ft.

The automatic daylight-responsive controls must be capable of reducing lighting power via continuous dimming with a dimming range of 100 percent to 15 percent of full light output or lower; the controls must also be capable of turning Off the controlled general lighting. If the area includes occupant sensors providing light reduction, the daylight-responsive controls may dim lighting below the occupant sensor unoccupied setpoint but not raise the lighting above it.

The controls must be capable of being calibrated only by authorized personnel within the space with a readily accessible means of calibration.

Specific-application controls (C405.2.5)

The 2024 IECC designates control requirements for special applications such as display lighting and supplemental task lighting. These luminaires must be controlled by either an occupant sensor or time-switch control for automatic shutoff, plus a manual control enabling them to be controlled independently.

Lighting for nonvisual applications such as plant growth must be served by an independent time-switch control. However, note that Section C405.4 in the 2024 IECC requires that luminaires in greenhouses be controlled by a device that turns luminaires Off in response to daylight.

Interior parking garages (Section 405.2.9)

There are also special lighting control requirements in the 2024 IECC for interior parking garages.

Interior parking garage lighting may be controlled by either an occupant sensor or a time-switch control. Lighting power must be reduced by at least 30 percent within 20 minutes of vacancy, with each control zone limited to 3,600 sq.ft.

Where lighting for visual adaptation is provided at entrances and exits, these luminaires must be controlled by a device that reduces lighting power by at least 50 percent from sunset to sunrise.

Luminaires that are within 20 ft. of the perimeter wall openings must be automatically reduced by at least 50 percent in response to available daylight.

Sleeping and dwelling unit controls (C405.2.10)

The 2024 IECC includes a new section for sleeping and dwelling units and placed all control requirements and exceptions there.

In sleeping units and dwelling units in hotels, motels, and vacation timeshare properties, lighting controls must automatically turn all lights and switched receptacles Off within 20 minutes of the unit being vacated. Automatic shutoff is not required, however, if captive key override control is used to control lights and receptacles in units that have five or fewer permanently installed lights and switched receptacles.

In sleeping units located in congregate living facilities (e.g., dormitories), an appropriately marked manual control must be installed by the entrance that turns Off all lights and switched receptacles aside from bathroom and kitchen lighting. In bathrooms, an occupant sensor must be installed for automatic shutoff within 20 minutes of vacancy.

Controlled receptacles (C405.12)

The 2024 revision of the IECC contains automatic receptacle (plug load) control requirements. Specifically, at least 50 percent of all permanently installed 125V, 15A and 20A receptacles installed in certain areas such as enclosed offices, workstations, and classrooms must be controlled. At least 25 percent of branch circuit feeders installed for modular furniture not shown on the building plans must also be controlled.

The control function may be based on split-controlled receptacles (top controlled) or separately controlled receptacles installed within a 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, via an occupant sensor with a 20-minute time delay, or via a signal from another control or alarm system.

Exterior lighting controls (Section 405.2.7)

The 2024 IECC recognizes the total exterior connected lighting power to be the maximum rated wattage of all exterior lighting powered through the building’s energy service and building site lighting for which the owner is responsible.

Exterior lighting must be turned Off when sufficient daylight is present. Building façade and landscape lighting must be automatically turned Off at night at a minimum between midnight and 6AM, or no later than 1 hour after the closing of building or business operation, and back On no earlier than 1 hour before the start of building or business operation.

All other exterior lighting—typically operating from dusk to dawn—must be reduced during the night based on the same time scheduling limitations as façade and landscape lighting or based on activity detection. Dusk-to-dawn lighting power must be reduced by at least 50 percent after normal operating hours. Outdoor parking lot luminaires greater than 40W and with a mounting height of 42 ft. or less must be controlled with an occupant sensor to reduce power by at least 50 percent with a 15-minute time delay. For control of such luminaires, control zoning is limited to 1500W of lighting power.

Additional efficiency requirements (C406)

Buildings complying with the 2024 IECC must enhance energy efficiency by acquiring credits for implementing various stretch energy efficiency options. First introduced in the 2021 IECC, this section has been dramatically revised and expanded to delineate requirements by building size.

For lighting, options include energy monitoring, high-end trim lighting controls, occupant sensors installed in a greater number of space types and with a 10-minute time delay, reduced lighting power density, demand-responsive lighting controls, and automated shading. The option for enhanced digital lighting controls has been removed.

Demand-responsive lighting controls (C405.2.8)

In this new section, demand-responsive lighting controls are covered as an enhanced energy efficiency option in C406 and also in Appendix CI103.1. This requires at least 75 percent of the interior floor area in certain building occupancy categories to include demand-responsive lighting controls. This appendix is not mandatory and is subject to specific adoption as an ordinance by the jurisdiction to be effective as a requirement.

If demand-responsive lighting controls are installed, they must be capable of reducing the output of controlled lighting down to 80 percent or less of either full power or total output after receiving a demand response signal from a certified virtual end node (VEN). If high-end trim is implemented, the trim level is considered “full power” or “full output.” The lights should be continuously dimmed over a period of up to 15 minutes to reach the demand response level. After the demand response event ends, the controlled lighting must return to normal operation.

Functional testing and documentation (C408.3)

The 2024 IECC’s Section C408 requires project commissioning to ensure all installed building systems operate as specified. This includes functional testing for lighting controls and automatic receptacle controls as well as specific documentation requirements.

Functional testing is indicated for different control types: occupant sensors (lighting and automatic receptacles), time-switch controls (lighting and automatic receptacles), and daylight-responsive controls. In the 2024 IECC, functional testing requirements for high-end trim controls and demand-responsive lighting controls, if installed, are also included.

At the conclusion of the project, in addition to documentation provided by the functional testing party that the installed controls meet or exceed specified performance criteria, specific documentation about the lighting and control system must be provided to the owner for maintenance purposes.

Documentation requirements include a lighting control narrative (Control Intent Narrative) with recommended setpoints, operating and maintenance manuals, functional testing reports, submittal data indicating all selected options for lighting and controls, a schedule for inspecting and recalibrating lighting controls, and more.

Conclusions 

Commercial building energy codes are becoming increasingly stringent in regard to lighting and controls while evolving with technological change, and the 2024 revision of the IECC is no exception.

In the future, commercial building energy codes may evolve to focus on energy consumption and decarbonization rather than initial design power and control capability. In the meantime, the 2024 IECC is likely to be adopted by jurisdictions and used.

Lighting practitioners in jurisdictions likely to implement the 2024 version of the IECC should become familiar with its requirements, as there are some significant changes in regard to lighting and controls.

For more information, consult the 2024 IECC.