Menu Toggle Software

Nonresidential Daylighting

Measure Description

This CASE Report will use a comprehensive approach to daylighting design and control strategies that maximize the use of natural light while minimizing glare and solar heat gain. Specifically, this CASE Report comprises several submeasures to promote more efficient use of daylight and to generate more energy savings, including Automatic Daylight Dimming to 10 Percent, Relative Solar Heat Gain Coefficient Equivalent for Louvers, Exterior Shading Thermal Breaks, Cleanup and Improvements to Daylighting Design Power Adjustment Factors, and Mandatory Secondary Daylit Zone Automatic Controls.

Daylight Dimming to Off

This submeasure proposes to update the nonresidential automatic daylight dimming controls provision such that, for areas other than parking garages, when daylight illuminance is greater than 150 percent of the design illuminance received from the general lighting system at full power, the general lighting power in the daylit zone is turned off. This submeasure leverages the proliferation of solid-state lighting and its dimming capability in the nonresidential sector and takes full advantage of the 0-100 percent dimming range that is already required for LED luminaires and sources in Title 24, Part 6. The proposed dimming to OFF further aims to result in higher energy savings by promoting the 0-10V “dim-to-dark” LED drivers that cuts power to the LED light engines when dimming control voltage is close to 0V. The same dim-to-off result can also be achieved by other implementations, such as a 0-100 percent dimming driver with a power relay.

Mandatory Controls in Secondary Sidelit Daylit Zones (SDZs)

This proposed sub-measure would move the prescriptive requirements for automatic daylighting controls in secondary sidelit daylit zones (SDZs) to the mandatory section of the Title 24, Part 6 where all ther lighting controls requirements appear. Currently, the requirement for automatic daylighting controls in SDZs is prescriptive, which means that users who choose the performance approach can trade off other high efficiency features in the building against SDZ controls. This results in confusion and uncertainty during code compliance inspection about whether the controls in SDZs were traded off, or if they were required and installed. As a prescriptive requirement, it is less likely that there is reliable enforcement of the control’s requirements. By converting the SDZ controls requirements into mandatory requirements, this proposal will simplify the daylighting code and the compliance enforcement process and align the daylighting requirements in Title 24, Part 6 with daylighting requirements in ASHRAE 90.1. The proposed changes will also provide certainty about when daylighting controls in SDZs are required, which will make it more likely that lighting in SDZs are controlled with photocontrols.

High Performance Envelope Submeasures

The following measures were initially presented as Nonresidential Daylighting submeasures, but have been grouped, more appropriately, under Nonresidential High Performance Envelope.

  • Refine Prescriptive Exterior Shading Reflective Solar Heat Gain Coefficient Requirements
  • Exterior Shading Thermal Breaks

Shading Power Adjustment Factor (PAF) Improvements

The “Shading Power Adjustment Factor (PAF) Improvements” was largely comprised of code language changes to improve the clarity, consistency, terminology and syntax of the current code language. It was therefore moved to the Code Cleanup Initiative.

This submeasure would simplify and correct the existing language for the Daylighting Design Power Adjustment Factors (PAFs). Some features of the PAF are better placed in the mandatory sections of the code rather than the prescriptive sections so that those features are also required under the performance path. Requirements would also be reviewed to evaluate whether their modification or deletion can be justified so as to increase the opportunities for installation on projects and ease the burden of compliance.

While implementing the PAFs in the 2019 code cycle, various errors or ambiguities were uncovered that require correction. The set of savings calculations derived in the development of the PAFs in 2019 vary depending on spacing, tilt and reflectance. This set would replace the single PAF value in the performance path compliance software.

Relevant Documents

Measure proposals, supporting documents, and other outside references will be made public as they become available.

Provide Feedback

This measure description will be updated as research is developed to support the 2022 code cycle. For questions or suggestions, email Include the measure name in the subject line.


Give Us Your Feedback

The Statewide CASE Team values input from all stakeholders engaged in the Title 24, Part 6 code change process. We encourage the open exchange of code change comments and concerns.

  • Use the form above to provide feedback on this measure.