Lighting

Light and wellness: A circadian approach to lighting design

A growing body of research shows that lighting has a significant impact on people’s well-being
By Brian Stacy, IALD, LEED AP, Arup, New York City August 21, 2019
Figure 3: Even though Arup achieved WELL Gold certification for the Boston office, our designers always try to go beyond checking a box. We use our home projects to test the limits of lighting design and improve the advice we can offer on our next project. Courtesy: Arup

Learning objectives

  • Gain an understanding of the history of circadian lighting design research. 
  • Learn the basic principles of circadian lighting. 
  • Glimpse the future of the lighting design industry based on these recent trends. 

How do we, as lighting designers, consistently up the ante in creating environments that aren’t just functional, but beautiful and socially useful? By letting our physiological systems lead the way.  

Starting more than a decade ago, Arup’s lighting design team immersed itself in the latest groundbreaking research on circadian rhythms. Circadian rhythms are driven by internal biological clocks that operate on a 24-hour, day/night schedule meant to optimize the body’s physiology. 

The intent of circadian lighting design is to work in harmony with humans’ internal clocks by providing ample access to daylight or, when daylight is unavailable, modulating the spectrum and color of artificial light in symbiosis with the natural lighting cycle. This harmony should amplify occupant comfort and productivity and create a healthier visual environment and experience.  

Sounds easy enough, right? In reality, circadian lighting design is more of a lengthy experiment than an authoritative design standard. In fact, there’s no universally agreed upon guidance  yet. At Arupthe team is working to sort out the human and technical complexities behind this quite natural idea, determining best practice through extensive research and more than a little self-experimentation. 

Figure 1: Traditional office lighting design typically has one color temperature tuned to the horizontal work surface, whereas in Arup’s Boston office, we’re thinking about the quantity of light that actually reaches the eye as well as the color profile of that light. Courtesy: Arup

Research in action 

The basics of circadian lighting research started in the 1960s and 70s around seasonal affective disorder. In the 90s, Arup’s research and development team (the forbears of Foresight, Research and Innovation) put together its first research project focused on how seasonal affective disorder impacts office workers.  

Over the past five yearsArup has had several internal research projects where staff delve into the leading papers in scientific journals about the effect of lighting on the circadian system. This work created a knowledge base of the demonstrable positive effects circadian lighting can have on office workers, health care workers — particularly shift workers — and even hospital patients. Now in 2019, both the Illuminating Engineering Society and UL are developing reports on recommended practices for circadian lighting 

Toby Lewis, an Arup lighting designer from the San Francisco officenoted recently in conversation that the move toward circadian lighting was a natural step for our industry. Her point was that designers have been experimenting with electric lighting sources in the built environment for decades without even thinking about the physiological impacts. Now that the industry is starting to think specifically about thatLewis was rightly saying 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. 

Figure 2: A circadian lighting system requires a spectrum of color temperature and intensity that follows a specific light curve, adapting the quality of light based on the time of day, as well as the local conditions. Thus, the curve in Boston is going to be a little bit different from the curve in Los Angeles. Courtesy: Arup

One of the first projects where we could put our research into practice was the Kaiser Permanente Medical Center in San Diego. Implementing a circadian lighting system in the hospital was a natural way to improve patient recovery times and create a healthier work environment for staff — all while supplying Kaiser Permanente with regular data they can use for future design decisions 

In speaking with my colleague Jake Wayne from Arup’s Boston office, he posed the argument that because of the experimental nature of these systems, flexibility is vital. A key point Wayne made was that as research continues and we learn more about actual biological responses, our clients should have the ability to change their programming to update or modify how it is used. I couldn’t agree more. 

It’s no secret that better sleep leads to faster healing, but getting a decent night’s sleep in a hospital isn’t easy. Arup’s lighting designers designed an allLED room lighting system that delivers “cooler” (rich in blue wavelengths) light during the day to promote wakefulness and transitions to “warmer,” lowintensity light in the early mornings and evenings for rest and recovery. The lighting effectively reinforces healthy circadian rhythms, which quicken recovery time. 

Figure 3: Even though Arup achieved WELL Gold certification for the Boston office, our designers always try to go beyond checking a box. We use our home projects to test the limits of lighting design and improve the advice we can offer on our next project. Courtesy: Arup

Case study: self-experimentation 

Circadian lighting systems aren’t something our design team is just recommending to clients. Our most ambitious experiments are done on our own turf. Starting with large-scale renovation projects in our San Francisco and Boston offices and soon kicking off in Seattle, Los Angeles and Toronto, circadian lighting design is Arup’s new normal.  

Traditional office lighting design typically has one color temperature tuned to the horizontal work surface, whereas in the Boston office, we’re thinking about the quantity of light that actually reaches the eye as well as the color profile of that light. A circadian lighting system requires a spectrum of color temperature and intensity that follows a specific light curve, based on the time of day. And the curve in Boston is going to be a little bit different from the curve in Los Angeles. 

Figure 4: Arup’s Boston office was one of Arup’s first circadian lighting testing grounds. Now that we have similar systems in place for our San Francisco, Seattle, Los Angeles and Toronto offices, circadian lighting design is becoming Arup’s new normal. Courtesy: Arup

Research is still evolving on how to tune circadian systems based on their actual latitudes and natural spectrum. Our bodyclock cycles adjust to the fluctuations of light from sunrise to sunset, as well as to other factors like cloud cover. This stems from the fact that light affects the body’s stimulus in different ways. For instance, biological eye sensitivity for the suppression of melatonin peaks around the 460 to 475 nanometer blue range (basically suppressing a person’s biological cycle instinct to sleep). At the same time, the eye’s sensitivity peaks in the green range around the 550 nanometer for vision sensitivity. This is one area where there’s more exciting research to be done.  

The variable color temperature lighting and ambient light quality throughout the office far exceeds what industry standards like International WELL Building Institute qualify as circadian lighting. Even though we achieved WELL Certified Gold for the Boston office, our designers always try to go beyond checking a box. We use our home projects to test the limits of lighting design and improve the advice we can offer on our next projectAnd, of course, we’re working toward a healthier and more comfortable place to work. 

Figure 5: Color temperature recommendation in relation to human circadian rhythm. The x axis is hours in a day and the y axis is color temperature in degrees kelvin. Courtesy: Arup

Circadian lighting moves into the mainstream  

For a very long time, there’s been a separation between daylight and electric lighting and Arup has been at the forefront of work to integrate the two. Now we’re seeing an uptick in the rest of the industry.  

Circadian lighting, while still evolving, is no longer just a dreamLately we’ve seen requests from major commercial clients asking for large-scale, human-centered lighting systems in their new facilities. On the other end of the spectrum are consumer products featuring tunable whitelighting technology via an app on a smartphone. 

The future of interior and exterior lighting design certainly lies in this balance of quality daylight and electric light working together to support our human circadian adaptation. And the logical extension of this is that lighting design will eventually start to drive building shape and aperture. And it may happen sooner than you’d think. The healthiest, most comfortable and most productive spaces will be those designed from the inside out. 

To view a time-lapse video of Arup’s San Francisco office that shows how they company has programmed the color temperature of their lighting to shift throughout the day, click here.


Brian Stacy, IALD, LEED AP, Arup, New York City
Author Bio: Brian Stacy is a principal and global skill leader of the lighting design studio for Arup. He is a leading international daylighting, architectural lighting and lighting controls designer.