Indoor Lighting Controls

1. Parking Garage Daylight Adaptation Zones Nighttime Controls. This measure ensures proper visual adaptation for drivers entering parking garages at night by requiring lighting in the daylight adaptation zones to reduce the light level to that of the general parking zone from sunset to sunrise.
2. Require Occupant Sensing Controls in more Spaces. The space types currently being considered include computer rooms, exercise/fitness and gymnasium areas, financial transaction areas, laboratory, lobby/main entry, and lounge, breakroom, or waiting areas. Additionally, the requirement would trigger occupied standby controls in spaces where ventilation is allowed to be shut off and temperature set back when no occupant is detected. This would result in energy savings from HVAC systems.
3. Reduce Occupant Sensing Control Delay Time. This measure would reduce the time delay for occupant sensing controls from the current 20 minutes to 15 minutes.
4. Update Multilevel Lighting Controls Requirements. This measure aims to clarify the current code requirements on multilevel lighting controls and update the exceptions to better reflect the current technology. The proposal includes five elements:
   • Improve the code language in specifying manual dimmer requirements
   • Change the trigger for requiring manual dimmers from an LPD basis to a wattage basis to align the metric used for determining controls requirements across all mandatory lighting controls.
   • Revise the threshold for requiring manual dimmers for spaces in nonresidential buildings, which were previously determined based on traditional light sources, to reflect LED lighting technologies. The current proposed threshold is 50 watts for spaces in nonresidential buildings.
   • Remove references to multilevel lighting controls and directly specify continuous dimming capability in other mandatory control sections, such as daylight responsive controls and demand responsive lighting controls.
   • Require all daylight responsive controls to be implemented with continuous dimming, and manual overrides to daylight responsive controls timed or reset at the next ON cycle.
5. Make the Alternate Partial Daylight Test the only test method for the Daylight Responsive Control Acceptance Test. This proposed measure would remove the Partial Daylight Test method and make the Alternate Partial Daylight Test the only test method. This simplifies the acceptance test procedure and promotes better compliance with the daylight responsive controls requirements.
6. Improve the lighting controls acceptance test methods for luminaire-level lighting controls (LLLC). The proposed measure would improve the acceptance test methods by providing instructions for testing LLLCs when they are used as the control solution to meet the mandatory lighting controls requirements. The improved test method would reduce test burden and increase effectiveness for the Acceptance Test Technicians.

Scope of Proposed Code Change

Justification for Proposed Change

Several of the proposed revisions to the mandatory control requirements would bring Title 24 into alignment with ASHRAE 90.1 lighting requirements and increase energy savings. The nighttime adaptation compensation controls for the parking garage daylight adaptation zone are an existing requirement in ASHRAE 90.1, and such controls are considered a best practice to increase safety from an illuminating engineering standpoint. ASHRAE 90.1 also requires more spaces to implement partial or full OFF occupant sensing controls, and some of those spaces are currently either not required to have occupant sensing controls or not included as an area category in Title 24. Reducing the maximum time delay of occupant sensing controls to 15 minutes saves energy and aligns with the publication of Addendum BD to ASHRAE 90.1-2022, as well as the default settings for many brands of occupant sensors.

The 0.5 watts per square foot threshold for requiring multilevel lighting controls has been in place since the pre-LED era and was based on traditional light sources. With LEDs’ high efficacy and being continuously dimmable with no or minimal additional cost, it would be prudent to recalibrate and revise the threshold based on current technologies. The multilevel lighting control is the only mandatory lighting control requirements that use an LPD-based trigger, while all others use a wattage-based trigger, creating confusion and compliance complexity for market actors. Furthermore, the code language for multilevel lighting controls has been ambiguous as to whether it pertains to continuous dimming that other controls can utilize or a physical dimmer for manual dimming. Since several other mandatory control sections reference multilevel lighting controls, it is essential to clean up the multilevel lighting controls code language to ensure those references are consistent and coherent. The current exception for multilevel lighting controls also creates a conflict with daylight responsive controls when a space is exempted from multilevel lighting controls but is required to implement daylight responsive controls. Without continuous dimming provided by multilevel lighting controls, daylight responsive controls would not be effective, and the resulting behavior could be perceived negatively by the occupant. The proposal of requiring continuous dimming for daylight responsive controls regardless of the multilevel lighting controls exception aims to address this conflict.

Requiring manual overrides of daylight responsive controls to be timed or reset at the next ON cycle is a code cleanup effort to address ambiguity in the current code language that does not clearly specify whether daylight responsive controls can be overridden by any user and how and when daylight responsive controls should resume when overridden.

The Alternate Partial Daylight Test was proposed and adopted in the 2022 T24 energy code as an alternative to the original Partial Daylight Test, as creating a proper test condition for performing the original Partial Daylight Test is often difficult. The intent was for the two test methods to coexist for a few code cycles, allowing Acceptance Test Technicians’ (ATTs’) to make a smooth transition to the Alternate Partial Daylight Test. It is time to formally remove the less effective Partial Daylight Test to improve acceptance test effectiveness and increase the compliance rate.

Current lighting controls acceptance test methods were designed for zone-based controls, where the lights in the entire zone, e.g., a daylit zone, are controlled by a single sensor. When luminaire-level lighting controls (LLLC) are used as the control solution to meet mandatory control requirements, the sampling rules in current test methods create a test burden, as too many controls would need to be tested. Additionally, the current test methods need to consider the independentedness of each LLLC luminaire in responding to changing daylight conditions and provide specific instructions for correctly and effectively performing the Full Daylight Test.

Relevant Documents

• Indoor Lighting Controls Measure Summary

CASE Reports

• Indoor Lighting Controls Draft CASE Report

Round One Utility-Sponsored Stakeholder Meeting Materials

• Indoor Lighting Controls – Proposal Summary
• September 24, 2025 Meeting Notes
• September 24, 2025 – Presentation Slides