May 7, 2026
Lighting People Remain Divided Over Human-Centric Lighting
RP-46 discussion reflects differing perspectives on circadian light exposure
Lighting people disagree on plenty of things. Warm versus cool color temperatures. Decorative fixtures versus architectural restraint. Uniform illumination versus dramatic contrast. In most cases, those differences get sorted out among project stakeholders, with room enough for more than one reasonable answer.
But occasionally, even the underlying lighting science becomes contested terrain. And few subjects in modern commercial lighting generate more sustained disagreement than circadian, or human-centric, lighting. The question of how much light the human body actually needs, at what times, in what spectral quality, and under what conditions has occupied researchers, standards writers and lighting specifiers for years. It has not resolved itself with widespread consensus.
A Researcher Raises His Hand
The latest episode occurred when Dr. Martin Moore-Ede, a former Harvard Medical School professor and one of the more credentialed voices in circadian biology, published a pointed critique of ANSI/IES RP-46-25, the Illuminating Engineering Society's recommended practice for supporting the physiological and behavioral effects of lighting in interior daytime environments.
Moore-Ede's piece, entitled Lighting Industry Attempts to Minimize the Need for Circadian Lighting, stated that RP-46 minimizes the importance of circadian amplitude, what he calls the "robustness" of circadian entrainment, in favor of a more modest baseline standard.
He contends the document takes a selective view of available research, understates the need for higher daytime blue-enriched light exposure in interior environments, and leans on a reading of scientific consensus that he does not accept. He has cited a survey of circadian researchers as evidence that expert opinion points toward stronger daytime light requirements than RP-46 reflects. His position: "Entrainment must be robust to promote good health."
It is worth noting that some of Moore-Ede's commentary moved beyond scientific disagreement into criticism of the standards-development process itself, including questions about institutional motivations.
What IES Said
The IES response, provided to Inside Lighting directly, was methodical and institutional in exactly the way one would expect from an organization that has spent decades writing standards under ANSI process requirements.
On the core question of circadian robustness, IES stated that RP-46 "fulfills its intended scope," and that expectations beyond that do not indicate a deficiency in the document. The recommended practice, the organization noted, was designed to support the physiological and behavioral effects of lighting in daytime interior environments, not to prescribe a full 24-hour circadian optimization program. Scientific consensus on what "optimal" circadian lighting actually looks like, IES argued, does not yet exist, and individual light sensitivity varies considerably across populations.
On the question of quantitative thresholds, the IES position was equally measured: "RP-46 intentionally supports a balanced, broadly applicable framework rather than fixed quantitative thresholds for circadian optimization." The organization also pushed back on Moore-Ede's use of the researcher survey as evidence of consensus, pointing out that the survey polled circadian researchers on broad questions about the importance of light, which few would dispute, while not including experts from visual science, clinical practice, or other relevant disciplines.
Procedurally, IES noted that Moore-Ede did not submit comments during the formal ANSI public review period, where his observations would have been considered and responded to directly by the committee.
This Conversation Has Been Going On Longer Than That
The tensions surrounding RP-46 are not new. In April 2018, the IES gathered researchers, scientists, and lighting professionals in Midtown Atlanta for its Research Symposium on Light and Health. The sessions were largely civil, though not without friction. What became clear, even then, was that the science was advancing faster than any consensus about what to do with it.
Then in August 2023, Randy Reid of Edison Report published a lengthy piece that blended reporting, commentary and advocacy. Drawing on conversations with IES RP-46 committee members and others involved in the process, Reid described what he viewed as deep procedural and governance problems, accusing the standards development process of "bad management, secrecy, turf fights, and politics." He called the resulting document a "convoluted mess" and described specific procedural choices during committee balloting as "bizarre questionable practices." His aspirations for the document were unambiguous: "My aspiration is that it faces rejection."
The article also raised concerns about conflicts of interest among committee members, the exclusion or marginalization of certain research perspectives, and what Reid described as a “veil of secrecy” around the process.
Days after publication, Reid was referred to the IES Ethics Committee. The article was later removed from Edison Report without public explanation, though an archived version is still available.
Where the Disagreement Actually Lives
None of this necessarily means one side is correct and the other wrong. Lighting has always accommodated competing philosophies, and specifiers routinely produce excellent work while disagreeing about color temperature, controls architecture, and daylighting strategy.
Circadian lighting may simply represent a more consequential version of that same reality: a field where evolving science, energy considerations, practical application constraints, and standards process requirements intersect imperfectly. The IES is not wrong that standards consensus and research consensus are different animals. Researchers are not wrong that the gap between those two things has real consequences for what gets specified in buildings where people spend most of their waking hours.
For lighting people, the more useful question may be less about who won this particular exchange and more about what comes next. RP-46 exists. Circadian research continues to develop. The distance between those two facts is where the next round of this conversation will take shape.
