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Advanced Daylighting Topics

Nonresidential Lighting

Codes and Standards Enhancement (CASE) Report

The Statewide CASE Team is requesting feedback on the 2019 Title 24, Part 6 Draft CASE Reports. The CASE Report presents pertinent information that supports the code change proposal. Please email feedback to You may also submit written comments to the Energy Commission. See the agenda for Energy Commission pre-rulemaking workshop (available here) for instructions on how to submit comments to the Energy Commission’s docket.

Draft CASE Report: Nonresidential Advanced Daylighting Design

Measure Description

Proposal A: Power Adjustment Factors

The proposed measure will allow Power Adjustment Factors (PAF)* for indoor lighting that are controlled by daylighting controls when certain technologies are installed in the proposed building. The PAFs may be applied to any nonresidential building subject to the provisions of Title 24, Part 6.

The proposed technologies include: fixed slats (louvers), daylight redirecting devices and clerestories. These technologies tend to increase the likelihood that glare is mitigated (e.g., fixed slats) and/or have the ability to increase the daylight potential (area or number of hours) of a space.

Previously, no credit could be taken for certain innovative technologies which increase the daylight potential of a space. Offering PAFs for these encourages their use. It is possible that the introduction of these technologies into the 2019 update may provide a gradual path to their prescriptive requirement in future updates.

Proposal B: Min VT Interpretation for TDDs

An interpretation of the Minimum Visible Transmittance (Min VT) requirement for plastic skylights (Table 140.3-C) is proposed for Tubular Daylighting Devices (TDDs). This is based on a new National Fenestration Rating Council (NFRC) Test Procedure (NFRC 203) for TDDs.

Proposal C: Update to Daylit Zones Definitions

An update to the Skylit Daylit Zone definition is proposed to ensure proper interpretation for skylights in atriums, and to the Sidelit Daylit Zones definition for cases with large exterior overhangs.

*Power Adjustment Factors are multipliers on the proposed design’s lighting power. From a compliance perspective they effectively reduce the proposed design’s lighting power. As such, a higher lighting power may be reduced enough to meet the maximum allowed lighting power of Title 24, Part 6.

Request for Feedback

The Statewide Utility Team encourages participation in the CASE Report development process through the submission of data—both primary sources and references to existing data. We are requesting data on areas such as energy savings, costs, market impacts, industry practices, barriers to code compliance, etc. from stakeholders. The data will inform the energy savings estimates, cost-effectiveness analysis, compliance and enforcement, and market impacts that will be presented in CASE Reports.

Do you have feedback or data to share? Send us an email at

California Statewide Utility Codes and Standards Program

This program is funded by California utility customers and administered by Pacific Gas and Electric Company, Southern California Edison, San Diego Gas and Electric Company, Southern California Gas Company, Sacramento Municipal District, and Los Angeles Department of Water and Power in preparation for the California Energy Commission’s Codes and Standards Buildings Advocacy.