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New research on circadian entrainment and the expanding understanding of the non-visual photoreceptors makes headlines daily; we’re up to five different types of ipRGCs in the retina. With a skeptical take on all the hype, lighting designers at Arup are taking a hands-on approach. They are exploring the technology in-house and sharing results among their design teams across the globe. Jake Wayne, senior lighting designer, leads Arup’s Boston lighting group, and Toby Lewis is a senior lighting designer at Arup’s San Francisco office. They have developed and continue testing a dynamic circadian white lighting system in their own offices, with their own employees here in the US. Wayne and Lewis use this experience to educate clients: emphasizing psychological benefits, discussing the potential health and productivity impacts, and specifying flexible systems as the research evolves.

"The reality is, we’ve been experimenting with electric lighting sources in our built environment and after the hours of daylight for decades and decades – a hundred years – without even thinking about the physiological impacts. Now that the industry is starting to think specifically about the physiological impacts, I think that shifting color temperature in indoor lighting systems to more closely match what’s happening outdoors is a reasonable next step in the electric lighting experiment," Lewis said. "There’s still a ways to go to really understand how much these tunable systems, or WELL‑tailored systems, are impacting human health."

Arup has been designing and deploying dynamic circadian lighting for its clients since before there were dynamic circadian, or "human-centric," standard products on the architectural lighting market – winning the Lighting Control Innovation Award at the international Illumination Awards in 2017. The WELL-certified Arup Boston office employs tunable-white lighting on a circadian schedule. Lewis’ San Francisco office followed suit, and Chicago’s system is undergoing commissioning. Designing new offices for Arup in Downtown Los Angeles, Dan Foreman, the lighting team leader who recently joined the LA office, is exploring a "daylight‑integrated, tunable‑white" lighting design.

Tunable white goes beyond the WELL Building Standard, which focuses on delivering vertical illumination and equivalent melanopic lux (as well as daylighting, visual acuity and comfort). "We feel that there’s also a psychological benefit to having the color shift. The reality is that most people working in a tunable-white space may not notice that the color changes with time of day. It is intended to be a subtle transition. But there is a subconscious effect when the conditions in your built environment make you feel more connected to the changing conditions that are happening outside. More research attention in this area would be beneficial," Lewis said.

There are two components to this: matching the color dynamics that are generally seen in daylight and adding dynamics to interior spaces away from daylighting. "There’s benefit to both. But the real question is, are these spaces that people will occupy for extended periods: at least 4 hours throughout the day? In San Francisco, our conference rooms, for example, don’t have tunable pendants because they’re not places where the system would have high impact on people. When cost choices need to be made there should be an underlying logic to guide the decision making," she said.

The Arup lighting design in their Boston offices
In their Boston offices (here and at top), the Arup lighting design team has experimented with various circadian lighting routines. Preliminary survey results show a preference for dynamic over static lighting.
Working in the lab

Wayne explained that the primary Boston lighting solution crossfades two channels of white LEDs, using DALI controls with a primarily indirect pendant lighting system. CCT and light levels are shifting throughout the day; from about 3000K early to 5000K midmorning through the afternoon (peaking at 40 fc average), to 3500K through the evening hours. "We warm it back up again, as well as leveling off then reducing the intensity over the course of the afternoon. We’re helping people kind of wind down at the end of their day, using light as the primary mechanism."

Arup is experimenting both with astronomical timing and with workday schedules. "Part of the fun of having this system in our office is we’re using it as a big testing lab, essentially," he said. "We’re trying to understand, does it make more sense to do it based on the schedule of when people are in the office? Or with the sunset?"

In some spaces, direct troffers, slot lighting, coves, decorative pendants – a variety of fixtures – demonstrate tunable white with a high-end aesthetic. They’re RGB with DMX control, crossfading 0‑10V, or proprietary systems. "We want to test out all the different types and technologies to control lighting and really learn from it as designers that live with it as well," Wayne said.

Based on their experience in-house, Arup teams can better inform clients that are trying to separate hype from value. "We work with our clients and think about how they want to use light. Give them the tools to make their own decisions," he explained. "Especially when you’re talking about healthcare institutions." Compared to a static system, additional components and significant commissioning are involved. "If you’re in California, where code requires a centralized control system, or if you have a high level of sophistication to your control system, the added complexity of tunable white lighting may not actually be that difficult, depending on the application." He cited the biggest challenge as lack of standardization in the marketplace. "It adds complexity for the design team to figure out a smart solution and manage that cost impact."

Arup's lighting design in their San Francisco office
Arup’s San Francisco employees start the day in a warmer, welcoming atmosphere. The energy level and CCT ramp up mid‑morning, peaking around 1:30 pm.
Psychological vs physiological

Wayne and Lewis both emphasized the psychological impact of circadian lighting systems, and they were careful not to overstate the known benefits to human health "The key is to have a system that is adaptable," Wayne said. "As research continues and we learn more about actual biological responses, clients should have the ability to change their programming, to update it or change how they use it."

Lewis explained the strategies and unique challenges found in the San Francisco office design. In open offices and core collaboration spaces, primarily indirect pendants and column graze lights provide circadian lighting in concert. "Unforeseen field conditions required us to change the spec of the column graze fixture and switch to a different manufacturer," she explained. Just commissioning the controls produced discordant color-and-intensity curves, because chips from different manufacturers produce light at different locations on the black body curve. Even using a luminance meter to synch the CCT and spectral power of each light source failed to produce harmony between the two luminaire types. "We had to visually tune one light source to match the other. That’s one of the ongoing challenges as these systems get implemented: how do you ensure color and intensity consistency across manufacturers?"

Lewis incorporated an astronomical timeclock that varies the circadian lighting cycles with the seasons. Wayne countered that Arup has guidelines, but preferences differ in less-sunny climates: "These are things we’re learning and investigating. There’s so much research ongoing; I don’t think any of us claim to have the best answer." But as Arup’s in-house surveys in Boston progress, the lighting design team is seeing a definite preference for the dynamic circadian lighting system over the static.

"Clients are certainly interested and motivated to look into whether this technology is right for them. Again, it all comes down to education and explaining where the research is. Really making sure they understand in their unique situation, what’s the best value? And from a design point of view, as well – does it make sense? Then applying it in such a way that aligns with their ability to maintain and operate the system," Wayne said. "We have to change our mindset to be more tuned-in to the ongoing operation of these systems and really understand it as we design…. Ultimately, what we design, they have to live with."

Lois I. Hutchinson

About Lois I. Hutchinson

Lois I. Hutchinson is a freelance writer specializing in lighting and energy issues. She is also the content marketing mastermind behind Inverse Square LLC, a Los Angeles–based consultancy. Contact her via with your comments and any article ideas that concern the lighting community here in the Southwest.

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