What is Circadian Lighting?
Various sectors, from healthcare to corporate, have begun to explore the potential benefits of lighting that follow the natural sleep/wake cycles of the human body. Known as circadian lighting, these strategically designed systems may have the power to positively affect people’s health, alertness, productivity, and more.
The concept of circadian lighting follows that of the human circadian rhythm, a 24-hour internal clock that cycles between tiredness and alertness at regular intervals. The area of the brain called the hypothalamus controls each person’s circadian rhythm by receiving signals from the eyes that report when it’s daytime and nighttime. The hypothalamus, in turn, controls the amount of melatonin released to correlate sleepiness with darkness and alertness with lightness.
Research has indicated that light affects both our visual and non-visual systems and that electric light can impact circadian rhythm. Circadian lighting is a concept that involves changing the and correlated color temperature (CCT) of lighting fixtures to coincide with the typical human circadian rhythm. We experience cooler color temperatures (ranging from 4000K up to about 10,000K) when the sun is highest in the sky and people are typically most alert during the day. Therefore, cooler CCTs are used in spaces and during times when it’s appropriate to promote alertness and attention.
On the other hand, warmer color temperatures (ranging from <2700K to 3500K) represent daylight hours when the sun is rising and setting, when people are falling asleep and waking up. Circadian lighting systems are set to adjust based on the CCT we typically observe at any given time of the day.
Circadian Lighting Applications
Healthcare centers are increasingly exploring circadian lighting. Studies are investigating the possible benefits to the health and recovery of long-term hospital patients. At Saint Barnabas Medical Center’s Cooperman Family Pavilion, the goal within the neonatal intensive care unit (NICU) is to increase the newborns’ exposure to natural daylight with the intention of regulating their circadian rhythm. Michael Barber and Ryan Conover specified a tunable white LED lighting system, which is programmed to adjust color temperature based on the time of day. Changes from cool blue to warm amber throughout the day is intended to support the newborns’ and their families’ natural sleep/wake cycles.
In education settings, circadian lighting may be able to influence the attentiveness and focus of students. Autonomous changes to color temperature can support natural light cycles while balancing the available natural and electric light, which has the potential to focus attention and elevate the overall mood in academic spaces.
WELL Standards for Circadian Lighting
The International WELL Building Institute (IWBI) established the WELL Building Standard to lead the design of buildings and communities to enhance comfort, health, and well-being. The IWBI offers circadian lighting standards for work areas, breakrooms, living environments, and learning areas. Feature L03, Circadian Lighting Design, is in place to provide users with appropriate light exposure in order to enhance circadian rhythms. In order to obtain points for this feature, all regularly occupied spaces in the project must have lighting that achieves a minimum of 120 EML (equivalent melanopic lux). Melanopic lux is measured on the vertical plane at the eye level of the occupant (about four feet off the ground). Feature L03 is an effort by WELL to create a metric for melanopic vision, which takes into account not only visual perception but also the biological impact of light. By offering circadian lighting standards for a variety of spaces, the IWBI can ensure designers are successfully using light to support humans’ visual and non-visual needs throughout.
As more studies and market sectors explore the uses and benefits of circadian lighting, designers will continue to refine the ways this concept can support people’s health and well-being in a variety of settings.