This course is part of the Custom Home Academy

The Potential of Tunable Lighting

While daylighting has many benefits, including helping to keep circadian cycles in sync, people often are not exposed to enough of it throughout the day. Sometimes there simply is not enough natural light available, whether because of the design constraints of a building or because of the season or geographic region in which a project is located. Consequently, artificial lighting can play a vital role in supplementing daylight and promoting the well-being of building occupants.

Until recently, much of the research on daylighting has focused on the benefits of daylighting in a number of building types, including retail shops, offices, and health-care settings. Now, a new wave of research is focusing on how exposure to natural light can help regulate the body’s circadian rhythms.

The combination of exposure to high-intensity blue light during the day and minimal exposure to such light at night is key to ensuring circadian cycles stay in sync. Unfortunately, modern life promotes exactly the opposite: too little time outside during the day and too much screen time at night.

While building design using the strategies outlined in the previous section can go a long way to ensuring adequate exposure to natural light, in some cases, natural light may need to be supplemented with artificial lighting to receive these benefits.

Most electric lighting is designed to meet the visual requirements of occupants; however, both higher light levels and shorter wavelengths are required to activate the circadian system.²¹

So-called tunable lighting can help ensure that building occupants are exposed to enough high-intensity blue light during the day, and that exposure to such light in late afternoon and evening is minimized.

New lighting technologies can possibly enable greater control over both the amount of light and its “spectral characteristics” (i.e., whether light is warm or cool). Both of these qualities can promote circadian processes and health. Increasing interest in how buildings can promote human health is driving the development of these technologies and research that attempts to quantify the benefits in a number of settings, from health care to classrooms.

There are several types of tunable lighting. The simplest, sometimes called “dim to warm,” is available in a color temperature range of 2700–3000 Kelvin (K). These lights are dimmable; as the light dims, it becomes warmer. This type of lighting is a good option for homes and hotel rooms, as light in this color temperature range tends to promote relaxation. Light that becomes “warmer” as it dims simulates natural light as the sun lowers past the horizon and the sky goes dark.²²

White-tunable lighting, as the name suggests, allows a user to adjust the color temperature of a light without dimming it. White tuning allows users to change the color of light from warm to neutral to cool in appearance. These products have at least two sets of controllable LEDs, typically including a warm white color (around 2700 K) and another at a cool white color (5000–6500 K). These lights have many potential applications and may be used to create desirable conditions in a classroom or office, mimic light conditions outside, and possibly help support and even re-synchronize circadian rhythms.²³

Finally, color tunable systems include at least three LEDs of different colors. These can be “mixed” to create a broad range of white and white-tinted light. Though still being developed, these lights could have especially useful applications in schools and health-care settings.

Biodynamic lighting is a type of lighting in which the illuminance levels and color temperatures are designed to vary throughout the day, mimicking the natural pattern of sunlight.²⁴ Researchers are attempting to evaluate the benefits of this type of lighting, and while the benefits may be challenging to quantify, people are responding positively to biodynamic lighting in these experimental settings.

Research on Biodynamic Lighting

While still in early days, research is yielding some promising insights on the health benefits of biodynamic lighting.

In one study, dementia patients in a psychiatric hospital were exposed to biodynamic lighting that simulated daylight cycles. The lighting was installed in the common room. The results showed a decrease in the amount of daytime napping and in “nighttime wandering,” common in dementia patients. This study has important implications, as dementia is known to disrupt the circadian clock. Older people require more light to stimulate the “master clock” in the SCN; at the same time, they tend to spend little if any time outside.²⁵

Another recent study looked at the possible benefits of tunable LED lighting on energy, lighting quality, and health for residents and caregivers at a residential senior care center in Sacramento, California.

The Sacramento Municipal Utility District (SMUD) installed tunable-white LED lighting to learn if and how it affects the sleep patterns, nighttime safety, and other behaviors of the residents. They also wanted to create better conditions for staff so they could provide a high standard of care.

The LED systems included a combination of spectral tuning and dimming, and they were installed in the residents’ rooms, the adjacent corridor, and the nurse station.

With high-intensity cool light during the day and lower-intensity warm lighting in the evening, this lighting scheme was designed to suppress the production of melatonin from morning to midday, and to prevent the suppression of melatonin production in the evening and at night.

One of the difficulties of this type of research is that the benefits are hard to measure scientifically. However, staff noted several health-related benefits that could have been due—at least in part—to the circadian lighting. For instance, “agitated behaviors” such as yelling and crying decreased following the installation, and one of the residents showed a notable decrease in psychotropic medication. The number of patient falls also decreased after the LED installation, and residents also spent more time in the corridor where the lights had been installed.²⁶

A school district in Texas partnered with the U.S. Department of Energy to study the impact of tunable-white LED lighting systems in two classrooms: a fourth-grade reading and language arts classroom and an eighth-grade science laboratory.

The goals of this lighting system were different than those in the health-care setting. The system allowed teachers to vary the color temperature and intensity across four preset conditions. This enabled teachers to “set the mood” for students, using warmer and dimmer lighting to induce calm and cooler and brighter lighting to encourage alert, focused behavior.

The two teachers who participated in the study reported that they appreciated the ability to tailor the lighting to different classroom needs. They also noted that the lighting and controls allowed students to be engaged in choosing the settings for various classroom activities. Both teachers stated that the lighting system improved the overall learning environment.²⁷