Lighting People Remain Divided Over Human-Centric Lighting

Overview

Published by the trade news site Inside Lighting in May 2026, this unsigned news analysis examines the latest flare-up in a long-running argument: how much light, of what spectrum, at what time of day, does the human body actually need? The trigger was a public critique of ANSI/IES RP-46-25, the Illuminating Engineering Society's recommended practice for supporting the physiological and behavioral effects of daytime interior lighting, and the IES's formal reply. The article's real subject is the gap between what circadian scientists believe and what a consensus standards process can put on paper.

Key Findings

• Dr. Martin Moore-Ede, a former Harvard Medical School professor and prominent circadian biologist, argued in a widely read post that RP-46 plays down circadian amplitude and settles for a modest baseline instead of the robust daytime entrainment he believes health requires. His summary position: "Entrainment must be robust to promote good health."
• He contends the document reads the research selectively, understates the need for higher, blue-enriched daytime light indoors, and relies on a scientific consensus he does not accept, pointing to a survey of circadian researchers as evidence that expert opinion favors stronger requirements.
• The IES answered that RP-46 "fulfills its intended scope": it supports daytime interior lighting rather than prescribing a full 24-hour circadian program, no consensus yet exists on what optimal circadian lighting is, and individual sensitivity varies widely.
• The society defended its choice of a broad framework over fixed numeric thresholds, noted that Moore-Ede's survey polled only circadian researchers and omitted visual scientists and clinicians, and pointed out that he did not comment during the ANSI public review period.
• The article traces the friction back to the IES Research Symposium on Light and Health in Atlanta in 2018 and to an August 2023 Edison Report article by Randy Reid alleging governance problems in the RP-46 committee, which was later withdrawn and led to an ethics referral.
• Its conclusion: neither side is simply wrong. Standards consensus and research consensus are different things, and the distance between them shapes what gets specified in the buildings where people spend their waking hours.

Why It Matters for Daylighting

The whole RP-46 dispute is about how to approximate, with electric lighting, the daytime stimulus that daylight provides for free. Both camps agree that people indoors get too little bright, short-wavelength light during the day; they disagree only about how much electric light it takes to compensate. A building that admits real daylight through the roof sidesteps most of that argument, because daylight supplies the intensity, spectrum and daily variation that any circadian recommendation is trying to imitate. For warehouses and manufacturing plants, where a shift can pass without a worker seeing the sky, prismatic skylights are the most direct way to deliver the daytime half of the light-dark cycle, whatever threshold the standards eventually settle on.

The article is also a useful caution against overselling. Vendors of tunable "human-centric" fixtures often quote numbers the underlying science has not agreed on; a daylighting case built on energy savings, visibility and occupant preference does not depend on winning that debate.

About the Source

Inside Lighting is an independent U.S. trade news outlet covering the commercial lighting industry, its companies and its standards bodies. The piece carries no byline and runs about three pages in the library's printout, which includes advertising blocks that partially obscure one paragraph. Publication was May 2026. Read the full article at inside.lighting for the complete exchange, including links to Moore-Ede's critique and the archived Edison Report piece.