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UL Publishes Lighting Design Guideline for Circadian Entrainment

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May 22, 2020

Northbrook, Illinois, May 22, 2020 – Underwriters Laboratories (UL), a world leader in safety and performance testing and certification services, has announced the publication of DG 24480, Design Guideline for Promoting Circadian Entrainment with Light for Day-Active People. The first edition of the Design Guideline creates an optional baseline performance goal for indoor lighting specifiers and building owners to consider when seeking circadian entrainment in addition to quality illumination.

For over 100 years, designers have designed indoor lighting primarily to accommodate illumination for tasks, essentially for the horizontal work surface. This publication furthers the understanding of lighting’s impact on human health and well-being by adding design guidelines for indoor light that enters the human eye (vertical photopic illuminance). Alternate approaches utilizing different assumptions about the spectral sensitivity of the circadian system are also discussed. 

The DG 24480 approach utilizes the circadian stimulus (CS) method for specifying circadian-effective light, and the included recommendations have been tested in field studies demonstrating that light that promotes circadian entrainment will lead to better sleep, mood and behavior. In a task force led by Mark Rea, Ph.D. and professor of cognitive science at the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute, UL managed the procedures, including two public comment processes during which lighting design professionals, facility owners, lighting manufacturers, sleep scientists and others provided constructive input.

According to Dr. Rea, “Lighting isn’t just for vision anymore. It’s high time we had a valid, agreed-upon metric and some basic guidelines so that healthy lighting can be effectively delivered to benefit society.”

The task force relied on a cross section of expertise from industry, academia, medicine, government and other sources. “Diverse industry participation and feedback enabled us to produce DG 24480, an industry-leading document that lighting designers can use as an option in their work,” stated Adam Lilien, global business development manager at UL.

DG 24480 incorporates a quick guide with six steps to achieve the goals with specific lighting levels and times of day, a specification guide with worked examples and details of supporting research findings. The 65 cited research publications span five decades and emanate from the fields of neurobiology, endocrinology, physiology, illumination engineering, anthropology and sleep medicine. While the field is evolving, these optional non-visual performance goals of DG 24480 can help guide applications successfully achieve measures that benefit building occupants.

You can view DG 24480 for free or download it for $75.00. To create an account and access the Design Guideline, visit


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