The Uptake of Circadian Lighting

Guest Editorial: By Scott Roos, vice president of Product Design, Juno Lighting Group

Circadian Lighting, also known as human-centric or biophilic lighting, is a topic that is starting to be at the top of mind with lighting specifiers, allied professionals, and end users. While it is generally easy to understand the potential benefits of proper circadian lighting, many questions and challenges remain as to how to effectively design, commission and sell such systems that, at least for the time being, involve more cost, complexity and risk for the designer, installer and end-user. While we are still in the pioneering stage of circadian lighting, early adopters are already putting it into practice and experiencing positive results.

Examples of Early Circadian Lighting Applications

Shared findings and early adopter experiences reviewed at the first annual Human Centric Lighting Conference, held by the Human Centric Lighting Society on June 11, indicated that wider-spread adoption may be right around the corner.

Seattle Mariners™: The Seattle Mariners facility manager is hooked on human-centric lighting. His curiosity was initially peaked when reviewing the results of a 25-year statistical study of Monday Night Football where west coast teams dominated east coast teams in both wins and point spread. The generally held explanation is that because circadian rhythms drive peak athletic performance in the afternoon, the west coast teams gain a physiological advantage in both home and away evening games due to the three hour time difference. Understanding that athletic performance was linked to healthy circadian rhythms, the facility manager decided to install circadian-friendly lighting for the players. Today, tunable white lighting in the Mariners locker room and clubhouse is set cool and bright to stimulate alertness before and during games and to warm and dim after games to promote relaxation. Other sports teams are taking note of this model and are looking to install similar systems.

Renton, Washington, School District: The director of Facilities for the Renton, Washington, school district decided to implement human-centric lighting based on research that supported his objective to enhance the learning environment and increase student achievement through improved design and operation of facilities. Teachers at the school were excited to have more control of both the color temperature and lighting levels and chose the cooler 6500K as the default setting for all types of learning. Interestingly, they found that if they didn’t activate the high light level/cool color temperature (CCT) scene during a test, students would request the change as it would improve their concentration levels. The ability to adjust lighting also had a significant positive impact on special education students, many of which have light and spectral sensitivities.

The results at the school have been so encouraging that the 2015 Washington State Criteria for High-Performance Schools now awards a point for implementing tunable white lighting systems. Of note, this criterion cites that tunable white/circadian systems have shown an increase in reading speeds, as well as reductions in testing errors, classroom hyperactivity, and staff and student absences.

Vulcan Real Estate®: The corporate properties manager for Vulcan Real Estate, a Paul G. Allen company, piloted 100 tunable white fixtures in an office building in conjunction with their evaluation of the Well Building Standard®. As a result, they found that the number one element of employee satisfaction was having individual control of color temperature and light level. Most compelling was the positive feedback from employees with seasonal affective disorder who expressed gratitude for being able to improve their emotional state during the work day. Additional tunable white installations in Vulcan facilities are being planned based on the promising results of this trial.

Acceptance of Cooler CCTs in Commercial Interiors

Long-standing research on the impact that cooler color temperature spectrally tuned blue-rich light has on increasing visual acuity is becoming more widely recognized and appreciated in the context of circadian lighting implementations. Light rich in the blue spectrum causes a physiological response for the pupil to constrict, which improves visual acuity much like the depth of field increases when a camera’s aperture size is reduced. Photopic illuminance, and therefore, the metric of the footcandle, is also based on a limited two-degree visual field that excludes part of the contribution of the 507-nanometer peak sensitivity rods in typical daytime tasks. This research is detailed in the recent Illuminating Engineering Society (IES) TM24-13 technical memorandum, which recommends that lower footcandle levels can be used when illuminating select visually demanding tasks at higher color temperatures.

Advocates of using higher color temperature lighting in interior applications point out that while the Pacific Northwest Energy Lab places no restrictions on color temperature, the Design Lights Consortium® (DLC), which governs rebate eligibility for most of the country, does not allow CCTs above 5000K in interior spaces, which of course is a barrier to the adoption of circadian lighting systems. In support of lifting the DLC restriction on CCT, Brian Libel, principal of The Lighting Partnership and chair of the committee who authored IES TM24-13, has cited that research has repeatedly demonstrated that people easily adapt to – and actually prefer – working under cooler color temperatures.

New Medical Findings

The use of spectrally tunable lighting has also gained the interest of medical facilities based on research, and more recently clinical trials, by companies like Photokinetics. Photokinetics claims they have validated that timed exposures to specific spectra of light can improve patient outcomes for a variety of medical conditions and can increase the effectiveness of 60 percent of the pharmaceutical drugs administered today. Considering that the Affordable Care Act allows medical facilities to qualify for increased reimbursement rates based on demonstrating improved patient outcomes and satisfaction, spectrally tunable white lighting systems should enjoy a quick return on investment – which would be certain to spur adoption.

The use of spectrally tunable lighting in medical applications does raise some interesting questions and challenges. For example, at what point does a tunable white luminaire become regulated by the Food and Drug Administration as a medical device? And while a lighting designer may specify tunable white fixtures and fixture placement, the programming and administering of “light prescriptions” will most certainly be the domain of healthcare professionals. The line between architectural lighting control and software applications that deliver light prescriptions is also a little blurred. Early installations of tunable white lighting fixtures in medical facilities will certainly provide the basis for controlled studies which will help refine our understanding of how different spectra exposures impact healing, health and well-being. This will also provide the opportunity for the lighting and medical communities to cooperate and develop effective solutions that are easy to commission and maintain.

Technological Innovation

Beyond the healthcare industry, there are other encouraging signs of circadian innovation. In particular, during the Human Centric Lighting Conference, two innovators presented technology that hold promise to make the specification of circadian lighting easier.

Michael Herf, the creator of the popular f.lux™ software that removes blue rich light from computer and smart device displays, previewed his latest f.luxometer™ online tool which can be found at www.fluxometer.com/rainbow. The f.luxometer allows users to easily and quickly compare circadian blue light spectra in different light sources and devices. It also provides comparison factors including calculated melanopic lux and the relative circadian impact vs. being outside on a sunny day. As more light sources are added to the library, this will become an even more useful resource.

In the not too distant future, it is likely that lighting design software will be used to predict both photopic and melonpic illuminance. Ian Ashton at Lighting Analysts, creator of the popular AGi 32 lighting design software, is actively working on developing such software, which he acknowledges is quite a complex undertaking as many factors need to be taken into account including the spectral power distribution of both the light source and reflecting surfaces as well as the anthropometrics of the eye and brow structure.

Putting Human Centric Lighting into Action

The inherent higher costs and greater complexity of designing and implementing circadian lighting brings challenges when proposing it to a client. Mike Lambert of KCL Engineering uses the following method, which we can learn from:

  1. Introduce the concept of human centric lighting to your client.
  2. Present strong research, much which is already available, to support the proposed benefits.
  3. Install mock-ups in areas that are visible to key decision makers. Monitor and report on the results.
  4. Submit proposals for human centric lighting as an alternate bid to allow for a cost and benefit comparison vs. standard lighting.

KCL has active mock-ups with two Iowa schools and, based on results to date, anticipates both will install human centric lighting as 100 percent of its new lighting solution by the end of 2015.


While we are no doubt still in the pioneering stages of understanding and implementing smart, spectrally tunable white lighting systems, early adopter experiences and ongoing research are quickly validating the benefits. There are many challenges for lighting specifiers to understand, justify and confidently specify spectrally tunable circadian lighting systems for clients, but just like with other new technologies, these early adopters will pave the way for wider spread adoption.



Bio: Scott Roos, vice president of Product Design, Juno Lighting Group

Scott Roos has 35 years of experience in the lighting industry encompassing product design, marketing, product management and lighting education. During the course of his career, he has worked on products that have earned numerous patents and awards including the Industrial Design Excellence Award and the LIGHTFAIR Technical Innovation Product award. Most recently Scott has been focusing on circadian lighting, serving as an advisory member of the IES Healthcare Committee and as a member of the Human Centric Lighting Committee. Scott has a BFA in Industrial Design from the University of Illinois and an MBA from De Paul University.

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