Circadian Rhythms and Interior Natural Light
Circadian rhythms are physical, mental, and behavioral changes that follow a daily cycle. These cycles are set by a “master clock” in the brain and respond primarily to light and darkness in an organism's environment, regulating many of our daily cycles, including sleeping, eating, and hormone fluctuations.
The clock is generated internally, but it relies on signals from the external environment to synchronize it. Light is the primary cue governing our sleep and wake cycles.
Melatonin helps synchronize the circadian rhythms with the environment and the body. In addition to regulating metabolism and sleep patterns, the circadian system influences important functions such as heart rate, blood pressure, body temperature, hormone levels, and urine production. Because of its role in regulating sleep, melatonin can be used to treat sleep disorders and reset the biological clock after a major disruption, such as an overseas flight.
Not so long ago, human activity was dictated by the sunrise and sunset. While people have long used fire and fuel lamps to extend productivity before and after dark, it was not until the advent and spread of electric lighting that we seriously began to subvert the natural cycles of day and night.
Modern lifestyles and artificial lighting can potentially disrupt the body’s normal rhythms, particularly sleep cycles, with negative consequences to health and well-being.
Bright Skies at Night
With the plethora of streetlights, signs, billboards, security, and porch lights, it is often impossible to escape light pollution, which can cause circadian disruption. In fact, more than 80 percent of the world’s population lives under skies that are nearly 10 percent brighter than they would be normally. The problem is worse in industrialized countries, with 99 percent of Europeans and Americans living under light polluted skies.
Much artificial lighting has been converted to fluorescent lamps and/or LEDs. While this is certainly good news for improving energy efficiency
, both emit a high percentage of blue light.
In addition, most of us spend hours in front of screens, which also emit short-wave blue light. While light of any kind can suppress the secretion of melatonin, blue light at night does so more powerfully. Exposure to this type of light at the wrong time—say, right before bedtime
—can slow or even prevent melatonin production and prevent us from getting a good night’s sleep.
Dearth of Daylight
Ironically, many people suffer from the opposite problem: not enough exposure to natural light during the day.
Exposure to high-intensity blue light is key for regulating circadian rhythms; however, people are spending more and more time indoors, many in buildings without adequate daylighting. According to the Environmental Protection Agency (EPA), people spend 90 percent of their time indoors. If this time is spent in buildings with inadequate daylighting, it could be enough to disrupt circadian rhythms and impact the quality of sleep. Fortunately, there are many ways to bring natural light into buildings, to the great benefit of building occupants.
Glass, Daylighting, and Interior Natural Light for Well-Being
There are several key reasons to promote daylighting in buildings. First, daylighting reduces the need for artificial lighting and makes buildings more energy efficient. Second, daylighting is a biophilic design
strategy that connects building occupants to aspects of the natural world, including fresh air, sunlight, and views of the outside. Daylighting can promote social interactions and help create feelings of well-being
in building occupants. Finally, exposure to daylight supports our circadian rhythms and, by extension, the physiological processes that are vital to good health.
Many studies have quantified and documented the positive impacts of daylighting on the health and well-being of building occupants. Daylighting can promote employee productivity, help reduce absenteeism, and even boost retail sales. In health-care settings, daylighting and views of nature may aid in healing and reduce reliance on certain medications. The role of daylight and artificial light in supporting circadian rhythms is a newer field of research, but an exciting one.
Designers can create spaces that ensure occupants are exposed to natural light throughout the day, whether through the placement of windows, skylights
, and/or through open plans that ensure all occupants have access to natural light. Equally important, glass and shading options can also help balance the need for natural light with control of solar gain and glare.