Below is my contribution to the November issue of tED Magazine, the official publication of the NAED. Reprinted with permission.

White-light color tuning is one of the most exciting advantages of LED lighting, providing the ability to adjust luminaire color output across the white light spectrum. As the timed spectral emission of light plays a part in circadian lighting—the application of light to promote circadian health—this developing trend offers the potential to take tunable white more mainstream.

“Interest in tunable-white lighting is fueled by increased adoption of the WELL Building Standard and with more research demonstrating the positive impact tunable-white lighting can have on our moods and productivity,” said Rahul Shira, Senior Product Marketing Manager, Signify US (www.signify.com).

Tunable-white lighting products produce white light that can be adjusted over a range of correlated color temperatures, typically from a visually warm (orangish-white) 2700K up to a visually cool (bluish-white) 5000K or 6500K. This is accomplished via the relative dimming of separately controllable arrays of warm- and cool-white LEDs, or primaries. Other colors may be added to enhance the spectrum of available color output while maximizing color rendering across the dimming range. While some screwbase LED replacement lamps offer white-light tuning as a feature, it is primarily featured in luminaires.

As a new capability, tunable white has created new lighting applications. It can be used to change the apparent warming or cooling of a space, set a mood, visually emphasize room finishes or artwork, simulate daylight or candlelight, and signal activity changes in spaces such as classrooms.

As the industry develops best practices for circadian lighting, the primary utility of tunable-white lighting remains its ability to signal and support activity and mood changes for occupant productivity and wellbeing. Image courtesy of Hubbell Lighting.

“If implemented correctly, tunable-white solutions can enhance people’s moods by giving them a touchstone to the outside world, especially in spaces where they have no access to windows or daylight,” said Jeff Hungarter, Commercial Indoor Director, Cree Lighting (www.creelighting.com). “In combination with other design elements like ergonomic furniture and enhanced air quality, it can really influence the wellbeing of the people in the space.”

A promising demand driver is the potential role tunable-white lighting can play in circadian lighting and health, a relatively new aspect of lighting that deals with its non-visual effects. Circadian lighting encompasses light distribution (emphasizing vertical light to reach photoreceptors in the eye), quantity of light reaching these photoreceptors, how long and at what time of day the light is received, and the spectrum of light.

Regarding spectrum, scientific research suggests shorter-wavelength light (around 450-530 nm, bluish white) in the morning can promote circadian entrainment and thereby reduce the quantity of light required for it. As such, while the presence of tunable-white luminaires that deliver recommended spectra may not be enough on their own for circadian entrainment, they can play an important role.

These LED luminaires produce a skylight appearance and simulated daylight effect, using advanced lighting control and color tuning to simulate dawn-to-dusk, east-to-west travel of the sun. Image courtesy of Cree Lighting.

“Don’t be fooled—tunable-white lighting is not automatically circadian lighting,” Hungarter cautioned. “Tunable white can and will play an integral role when the lighting design is done to ensure quantity, timing, and other parameters for circadian lighting are met. Ongoing research and education are going to be key as we drive health and well-being into current and future lighting designs.”

This potential opportunity has created demand for design guidance. Currently, there are two guidelines for circadian lighting. One is UL’s Design Guide 24480, Design Guideline for Promoting Circadian Entrainment with Light for Day-Active People, which is largely based on Lighting Research Center recommendations and research, and the other is the WELL Building Standard, a points-based healthy building rating system that is potentially a significant demand driver for circadian lighting. Both account for spectral emission, which can be used to reduce quantity of light, though they use different metrics and WELL is more concerned with achieving a certain spectral profile (D65), while UL is more flexible.

The COVID pandemic has increased interest in designing around health and wellness. This is nominally good for lighting features such as disinfecting light, circadian lighting, and intelligent lighting control that enables space management, support of social distancing, and contact tracing. So far, however, tunable white has minimally benefited; the predominant beneficiary, at least in terms of interest, has been germicidal light.

“Designers are applying tunable white in education, healthcare, and higher-end commercial suites, where the circadian or aesthetic effects have value,” said David Venhaus, Manager of Training and Curriculum Development in the Lighting Solutions Center at Hubbell Lighting (www.hubbell-ltg.com). “COVID is driving more interest in disinfection options like UV-C or 405-nm visible blue disinfection lights.”

As a result, despite its utility, tunable white continues to face hurdles to adoption including a cost premium, more complex wiring, potentially more sophisticated controls, and a lower efficacy than fixed-color sources. While it is increasing in adoption, the market is still developing as end-users become more aware of its benefits and how to quantify these benefits.

This requires a conversation with customers that includes return on investment based on energy efficiency but also includes non-energy benefits of being able to adjust color appearance and resulting mood and atmosphere. The key to this transition and support of new lighting technologies like tunable white and intelligent lighting control is an educated customer and consultants like electrical distributors.

“Distributors can help guide end-user customers on their lighting decisions and advise them on how to shift their focus from energy savings-based ROI and take advantage of a combination of energy and occupant wellness-based justifications,” Shira said. “Moreover, distributors can add value by promoting qualified tunable-white lighting packages between fixture providers and control providers, with the understanding that manufacturers that offer both elements have robust and consistent performance and are capable of dealing with the complexity of correlated color temperature, intensity, and spectral tuning.”

“Invest the time, energy, and resources to establish a solid baseline understanding of the latest developments in tunable-white technology,” Venhaus advised. “Get familiar with the technology in the luminaires and the control systems used. And make sure you understand how the final end-user interface works because this is the key to a successful user experience.”

Craig DiLouie

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