Working by Daylight: How Circadian Lighting Increases Productivity

Our High Performance Buildings Group experts discuss how implementing circadian lighting benefits building occupants by improving health and productivity.

A recent study published in Building and Environment shows that patients with direct access to morning light were seeing their stays shortened by anywhere from 16 to 41 percent.

By now, we all know that low access to daylight can be detrimental to our health. Eye strain, exhaustion, and weakening mental health are all issues that share a root cause in poor access to light.

But what if the implications of access to daylight went beyond wellness and energy savings, and we could prove it was inextricably linked to increases in productivity? If we were able to determine hour by hour (even minute by minute) how optimized a person’s mind and body are under specific lighting conditions, we would be able to leverage that information toward creating a workplace that goes beyond simply housing business activity and improving the quality of work being done.

In fact, we already can. It’s called circadian lighting—a lighting system designed to tap into the proven cycles our bodies follow each day, based on the position, duration, and color of natural sunlight at any given time. These cycles are known to lighting designers and medical researchers as “circadian rhythms,” and a circadian lighting system is tailored specifically to maximize our functionality.

For example, in a traditional office space we tend to have electric lighting we can turn on or off. But there is rarely a distinction in the color of that light or its brightness. Think of fluorescents hanging uniformly below a white dropped ceiling—your eyes may be hurting already. This works against occupants’ naturally occurring circadian rhythms and can cause dramatic decreases in overall wellness and productivity. Circadian lighting systems mimic the behavior of the sun and incorporate it into the environment, benefiting occupants by creating a comfortable space and increasing productivity. This can be achieved with a few methods that we’ll explore in this article, including introducing natural light into areas through architectural elements and by mimicking the solar sequence through tunable LED lighting.

The Biological Element

When we examine the pattern of the sun through its 24-hour cycle, we notice that the light it emits is more complex than simply light or dark. The color and intensity of sunlight changes throughout the day: warm amber light at sunrise slowly changes into a cooler, brighter light during the afternoon, before warming back into an amber light at sunset. Human vision follows this cycle throughout the day. The eye consists of photoreceptor cells—rods, cones, and intrinsically photosensitive retinal ganglion cells (ipRGCs)—that play a vital role. Cones sense changes in color and bright light, while rods sense changes in low light levels. The eye sends these signals to the brain to form images and trigger the release of serotonin (the body’s natural antidepressant) during the day and melatonin (a hormone affecting sleep) at night. And perhaps most importantly, ipRGCs, which are located at the lower back of the eye, send blue light information to our brains and act as an internal timekeeper, using the different intensities to synchronize our bodies to the 24-hour light cycle. This is what creates our circadian rhythm and promotes our mental and physical health, our mood, and our energy.


Lighting designers leverage data on how the human body reacts to light to create a system that understands the type of light an occupant needs to perform at optimum levels on an hour to hour (or even a minute to minute) basis. Just like with a healthy diet, if we feed the body what it needs, it will perform better.

The benefits of human-centric circadian lighting design include:
  • Faster cognitive processing
  • Increased alertness in the morning
  • Improved mood, productivity, and concentration
  • Improved sleep
  • Reduced hyperactivity
  • Reduction in errors and accidents

Recent studies show that office workers with the best possible view of natural light performed between 10 and 25 percent better on tests of mental function and memory recall. Those with poor views or no view at all (think high cubical partitions, heavy glare, basement offices, etc.) reported increases in fatigue and decreases in overall speed of performance. These variables can be controlled with circadian lighting design. Incorporating natural light in the architecture can boost not just the performance of a building, but also of those who occupy it as well.

Circadian lighting also has been shown to have useful applications in the healthcare industry, benefiting patients and institutions alike. A recent study published in Building and Environment shows that patients with direct access to morning light were seeing their stays shortened by anywhere from 16 to 41 percent.

How It’s Done

Existing technologies allow us to re-create the sun’s daily routine to help manage occupants’ circadian rhythms, particularly in spaces that have poor access to natural light. LED light fixtures can mimic the solar color shift with color changing technology and standard dimming to control intensity, creating health benefits similar to what we gain from daylighting. For LED circadian lighting to work, a controls system is needed to handle the job. Presently, that is the biggest cost. Numerous manufacturers have already designed their own systems, and it can be done using a variety of products. A full cycle of human-centric lighting has already become a reality for workplaces and healthcare facilities across the United States, and they are seeing the productivity benefits in real time.

Natural light has the most direct effect on our circadian rhythms and harnessing it for our interior spaces is the most effective way to optimize its effects. However, this means more than just allowing light into a space. Giant windows often overheat those nearby, do little to deflect glare, and leave much of the space unaffected. Proper daylighting involves controlling light and getting as much effective illuminance to target areas as possible while minimizing heat gain and glare. Architectural design elements like light shelves and louvers can bring more light into the interior of a building. They can also direct light deeper into a space. Exterior overhangs and vertical fins on the glazing walls of a building can help mitigate glare and heat gain.

Jake Herman, EIT, Lighting Designer

Images courtesy of Mario Gallucci