2024 IECC and Lighting Controls

Adopted by states and other jurisdictions, commercial building energy codes regulate the energy-efficient design of buildings, with the majority based on the International Energy Conservation Code (IECC), a model code.

In August 2024, the International Code Council published the 2024 version of the IECC, which has been updated every three years since 2000. As with previous iterations of the IECC, this new version reduces lighting power allowances, expands mandatory controls requirements, and issues clarifications.

This article starts with some background about commercial building energy codes and then describes the major lighting control requirements in the 2024 IECC, highlighting significant changes from the 2021 version. For greater specificity regarding requirements and exceptions, consult the IECC. For ultimate interpretation, consult the authority having jurisdiction.

Codes and standards

Energy codes may be adopted for residential or commercial buildings and at various levels of government including Federal, state, and local jurisdictions. At the state level, a majority have adopted codes based on the IECC; others base it on the ANSI/ASHRAE/IES 90.1 energy standard, developed their own code, or have no statewide code. As both the IECC and 90.1 are updated every three years, this presents a significant variety of energy codes across jurisdictions and a need to keep abreast of code developments. Note the IECC recognizes 90.1 as an alternative compliance standard, presenting 90.1 compliance as an option.

In an effort to promote energy savings, the Department of Energy (DOE) recognizes 90.1 as the national energy reference standard. Currently, the DOE recognizes the 2019 version as being in effect. In March 2024, the DOE determined the 2022 version saves energy compared to the 2019 version and now requires all states to adopt it or an equivalent by 2026 in order to receive enforcement funding, or justify why they cannot comply.

Below, we see commercial building energy code adoption in the United States as of September 2024, based on analysis by the DOE, which established categories of energy efficiency based on different version of 90.1 or equivalence to these versions. 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.

Scope of the 2024 IECC

The 2024 IECC applies to various energy-using systems (including electric lighting) installed in building new construction, additions, and alterations, including electric lighting. The lighting section (C405) contains prescriptive and mandatory provisions focused on prescriptive lighting power allowances, mandatory lighting controls, and functional testing of lighting controls, with various exceptions.

The 2021 version included the addition of daylight-responsive lighting control for secondary daylight zones, automatic power receptacle control, parking garage lighting control, and corridor lighting control. In the 2024 version, major changes include manual continuous dimming being specifically required in a range of space types, parameters for implementing an enhanced energy efficiency option for demand-responsive lighting control, and removal of the luminaire-level lighting control (LLLC) compliance path.

Also new to the 2024 version, for alterations, the exception was removed for projects involving replacement of less than 10 percent of interior luminaires (Section C503.5). For exterior lighting, a threshold of 400W was added. If wattage is increased by 400W, the IECC’s lighting power allowances apply. If the total wattage of new or replacement luminaires exceeds 400W, the exterior lighting control and related functional testing requirements apply, with a significant exemption for individual luminaires smaller than 50W that pass functional tests for automatic shutoff based on daylight.

Lighting control

Conceptually, the 2024 IECC aims to minimize energy consumption by automatically reducing or turning OFF lighting when it is not being used based on three inputs: occupancy, a time event, or ambient light level. Additionally, various manual controls are required for occupant convenience and additional energy savings with dimming, and zoning restrictions ensure independent control of lighting where needed. Functional testing requirements ensure the lighting control installation is vetted and supported by construction documents.

New to the 2024 IECC, the LLLC compliance path has been removed. Starting with the 2018 version, the IECC began offering two paths for interior lighting controls compliance: 1) a discrete approach that satisfies all the applicable requirements, and 2) a more direct approach of luminaire-level lighting controls along with occupant sensors, specific application controls, and manual controls. In the 2024 IECC, LLLC returns to being a compliance option rather than a formalized path.

Occupant sensing (C405.2.1)

Occupant sensors can be used where appropriate to satisfy requirements for interior automatic shutoff, but they are specifically required in a range of spaces. These are usually smaller, enclosed spaces such as classrooms and private offices but also include larger spaces such as warehouses and open offices, which can be divided into smaller zones with dedicated occupant sensor control.
New to the IECC in the 2024 version, computer rooms (data center), medical supply rooms (healthcare facilities), laundry/washing areas, and telemedicine rooms (healthcare facilities) have been added to the list of spaces requiring occupant sensor controls.

Where occupant sensors are installed, a manual Off control device is required, which may be remote or integrated with the occupant sensor. Otherwise, the sensor must turn the lights Off within 20 minutes of the space being vacated and feature manual-On or auto-On-to-maximum-50-percent-power operation. Full auto-On with no manual control is allowed in some applications, such as corridors and interior parking areas.

The 2024 IECC identifies three special applications for occupant sensors, with particular requirements:

Warehouse storage areas: The sensor must reduce lighting power by no more than 50 percent within 20 minutes of the area being vacated. Lighting in each aisle must be controlled independently. Lights that are not turned Off by occupant sensors must be controlled via a time-switch enacting scheduling. A manual control must be provided that enables occupants to turn the lighting Off.

Open Offices: 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 of full power. When all occupants have vacated all zones, the control system must turn all general lighting Off, or a time-switch may be assigned for this.

Corridors: Unless the corridor is lighted with the bare amount of illumination required for safety, lighting power must be uniformly reduced by no more than 50 percent within 20 minutes of the space becoming unoccupied.

Time-switch controls (C405.2.2)

Where occupant sensors are not installed, time-switch controls must be installed and programmed to automatically turn the lights Off when the space is predictably unoccupied based on a schedule, with notable exceptions.

The control must feature a minimum seven-day clock, backup capability in the event of power interruption, and “holiday” programming. New to the 2024 IECC, for spaces where schedules aren’t available, the control system must be programmed to a schedule that turns the lights Off at least 12 hours per day.

Users must be given override capability via a manual control device that is limited in zoning to 5,000 sq.ft. and keeps the lights On for no longer than two hours. Manual controls must be located so they are readily accessible to occupants and either enable the lights to be visible or otherwise indicate the area and status of the lights. In certain large facilities such as mall concourses and sports arenas, the override time may be longer (if the override is a captive key device) and the control area may be up to 20,000 sq.ft.

Dimming controls (C405.2.3)

Previously titled “light reduction controls,” this section has been thoroughly revised in the 2024 IECC. Eliminating bilevel switching as an option, this version requires 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, which we’ll cover in detail later in this article).

Dimming controls must be manual unless high-end trim lighting control is being implemented for the lighting. The lights must be continuously dimmable from full output to 10 percent of full power or lower, plus Off. Again, manual controls must be located such they are readily accessible to occupants and either enable the lights to be visible or otherwise indicate the area and status of the lights.

Daylight-responsive controls (C405.2.4)

The 2024 IECC requires that general lighting in daylight zones feature daylight-responsive controls that independently control the lighting, with exceptions. The IECC defines the dimensions of these daylight zones (primary and secondary) based on whether they are sidelit (adjacent to vertical fenestration such as windows) or toplit (under fenestration such as skylights).

Daylight-responsive controls are required in daylight zones as defined by the code if the general lighting reaches a wattage threshold, which the 2024 IECC reduced from the 2021 version for primary sidelit and toplit zones. If the space has primary sidelit and/or toplit daylight zones containing more than 75W of general lighting, daylight-responsive control is required. If the total wattage of general lighting in primary and secondary sidelit daylight zones combined is more than 150W, again, control is required. The lighting in sidelit and toplit zones must be controlled independently, as must lighting in primary and secondary sidelit zones. In the 2024 version of the IECC, the calculated exception to daylight-responsive controls in trade for lowering the lighting power allowance was removed, and an exception added for enclosed office spaces smaller than 250 sq.ft.

Controls must be automatic and provide continuous dimming down to at most 15 percent of full light output and be capable of turning the lights Off. Controls must be configured so they can be calibrated within the space, with the calibration means readily accessible. In warehouse storage areas and corridors where occupant sensing reduces lighting, daylight-responsive controls may reduce power further but not raise it above the level set by the occupant sensor.

Special applications (C405.2.5)

The 2024 IECC designates control requirements for special applications such as display and accent 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 separately from the general lighting.

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 calls out horticultural lighting and states that the luminaires in greenhouses must be controlled by a device that turns Off luminaires in response to daylight.

Interior parking garage lighting controls (C405.2.9)

The 2024 IECC requires lighting controls in interior parking garages. Interior parking garage lighting must be controlled by either an occupant sensor or a time-switch control. Additionally, lighting power must be automatically reduced based on occupancy with a time delay of 20 minutes and a control zone limited to a maximum of 3,600 sq.ft. At entrances and exits where lighting is provided for visual adaptation between indoor and outdoor brightness levels, this lighting must be reduced by at least 50 percent between sunset to sunrise.

Sleeping and dwelling unit controls (C405.2.10)

The 2024 IECC created a new special section for sleeping and dwelling units and identified all control requirements and exceptions there.

In sleeping units and dwelling units in hotels, motels, and vacation timeshare properties, at least two 125V 15- and 20-amp switched receptacles must be provided in each room aside from bathrooms, kitchens, foyers, hallways, and closets. Lighting controls must be provided that 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, 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.

Automatic receptacle controls (C405.12)

The 2024 version 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 applications 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 plans must be controlled.

The control function may be based on split-controlled receptacles (top controlled) or separate controlled receptacles must be 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 (C405.2.7)

With exceptions, exterior lighting must be turned Off when sufficient daylight is present or based on a schedule.

Building façade and landscape lighting must be automatically turned Off during the night when it is no longer needed, within set times. All other exterior lighting—typically operating dusk to dawn—must be reduced by at least 50 percent during the night based on time or occupancy.

Additional energy efficiency requirements (C406)

Buildings complying with the 2024 IECC must enhance energy efficiency by acquiring credits for implementing various stretch energy efficiency options listed on a table with applicable credits. 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 more applications and with a 10-minute time delay, reduced lighting power, demand-responsive lighting controls, and automated shading. Note that the credit for enhanced digital lighting controls has been removed.

Demand-responsive lighting controls (C405.2.8)

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

In either scenario, 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 full 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 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 certain documentation.

Specific 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. New to the 2024 IECC, this section now also includes functional testing requirements for high-end trim controls and demand-responsive lighting controls if installed.
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, the owner must be provided certain documentation about the lighting and control system so that they can maintain it.

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

2024 IECC decoded

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

In the future, commercial building energy codes may evolve toward a 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 put to use.

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

For more information, consult the 2024 IECC.