Lighting controls have elevated energy efficiency. Dynamic white lighting control is something different. Also known as tunable white lighting, it has the capacity to fine-tune LED light to better sync with our biological clocks. Such luminaire precision is poised to be the next frontier in lighting.
Government and university lab researchers continue to investigate artificial lighting and its effect on the human body, encouraging Acuity, Lutron, Philips and others to develop tunable-white lighting products. With the emergence of the International WELL Building Institute’s WELL Building Standard and the Center for Active Design’s FITWEL Certification System, building owners, design teams and contractors are beginning to understand and apply lighting to achieve a “healthy” building for occupants.
In a discussion of tunable white light, individuals speak to correlated color temperature (CCT)—light made warmer or cooler based on color spectrums. While dynamic white lighting controls can vary in sophistication from manual to programmed, they also vary in CCT range. The complex systems offer three color temperatures or kelvin (K) output capability (e.g., 3,000K, 4,000K and 6,500K). Some systems start at around 2,500K. Downlights and linear systems are the typical lighting forms for tunable white technology. Desk lamps have entered this space, too.
How color is made
Carl R. Ingling Jr., noted color and vision researcher at Ohio State University, wrote, “Color is a pigment of your imagination.”
Mark S. Rea, director of the Lighting Research Center (LRC) and professor of Architecture and Cognitive Sciences at Rensselaer Polytechnic Institute, further expanded on this thought.
“The eye computes the colors we receive,” he said. “Your head dictates how you see color. Wavelengths have no inherent color. Unlike the ear, the eye is not a frequency analyzer. As vernacular shorthand, we use the word ‘red’ to be synonymous with long wavelengths and ‘blue’ with shorter.”
Rea spoke at Lightfair International 2018 in Chicago. The LRC in Troy, N.Y., is a global leader in lighting research and education that includes solid-state lighting, light and health, transportation lighting, and energy efficiency. It hosted a number of lighting seminars at Lightfair.
Positively affecting the human circadian rhythm through the control of color wavelength is an increasingly important objective for tunable white light. In noted LRC studies sponsored by the U.S. Office of Naval Research, 200 lux of long-wavelength (red) and 2,650K lighting increased performance in short-term tasks. Forty lux of blue and red lights increased cognition and reduced sleepiness and relaxation. Exposure to 40 lux of long-wavelength light increased alertness in the afternoon. The same affect was found through exposure to 200 lux of long-wavelength red light and 360 lux of 2,650K light.
Robert Soler, vice president of human biological technologies and research for BIOS Lighting in Melbourne, Fla., presented at an LRC seminar on circadian lighting and the need for better lighting design.
“Biology does adapt to lighting,” Soler said. “While our biological clocks have evolved around the sun, modern society has broken this relationship. The question is, and the research continues, in how we can replicate what we have outdoors to indoors so we can properly guide our master clock. Our biology does synchronize to the light input indoors, though slowly.”
Soler explained providing bright lighting in the morning is important for initiating the “day” period for our bodies. Bright light at the end of the day is equally important for ending the “day” period of our biological clocks. There is a big benefit to providing high daytime signals during our biological daytime. The simplest way to achieve this is constant daytime light exposure.
“Quite frankly, bad lighting and bad lighting design have confused our biological clocks,” Soler said. “Indoor lighting tends to be too dim to be proper daylight and too bright to be night. Artificial light level requirements were designed without biology in mind. So the point is to create biologically brighter days and darker nights. The light spectrum can help do this without compromising color preference or intensity.”
Lighting design plays a role, too. Soler suggested lighting above the horizon with high photopic lux, high vertical lux and applying a melanopic-rich spectrum; perhaps use layers of light in the space. While this may be a more expensive approach, it has been shown to increase productivity, help achieve better academic performance, and better health.
The WELL standard uses melanopic lux (good blue) as a measure. This lux refers to how melanopsin-containing cells in your retina react to light. Such cells provide major input to circadian rhythms at high light levels. If melanopic lux values are too low (below 5), they will have little effect in changing circadian phases. Finding the right levels is important. WELL does make some recommendations. Its Part 54: Circadian Lighting Design, requires 200 melanopic vertical lux for a minimum of 4 hours or 150 for the entire day. Daylight can be incorporated to achieve this objective.
“Because today’s lighting design is all about comfort [e.g., glare, screen visibility, energy requirements], higher light levels aren’t considered,” Soler said. “So, healthy lighting techniques might create a tension in lighting preferences. But this is what happens in clinical and field studies when lighting a space with brighter daytime lights: early morning lights given to night owls significantly reduced ADHD [attention deficit hyperactivity disorder], improved cognitive performance in adolescents, and in the office, resulted in better mood for its occupants and better sleep at home.”
Because the science of indoor light’s effect on humans continues to be studied, Soler did advise avoiding promises in a healthy lighting strategy to elude liability. For example, use suggested language such as “Has been shown to do… .”
Applying dynamic white lighting
Finding the best way to apply dynamic white lighting requires understanding what an occupant does in that space and how lighting can support it. That’s a recommendation shared by Stewart Shell, project manager at Forte Building Science, a division of M.E. Group, in Omaha, Neb. Forte bills itself as a high-performance engineering firm focused on MEP systems. Helping create healthy indoor lighting that positively affects occupants is one aspect of Forte’s efforts.
“There is a psychological aspect to light and how it affects us,” Shell said. “Lighting can calm [and] improve mood. You are seeing tunable lighting applied in diverse settings from offices, schools and hospitals to correctional facilities. It’s a form of biomimicry. In the workplace, lots of lighting early in the morning is applied. We treat it as a dose of medicine. Research shows cognitive [function], and in part performance, are affected as is heart rate and cortisol levels. The morning is when we are becoming more alert and active. That’s what most businesses want and probably schools, too.”
Setting white light at 3,500K is still a very common starting point for designers, according to Shell.
“It’s safe,” he said. “You may be aiming for comfort with one client, but you might program lighting at a higher kelvin for say a call center, a nurse’s station or other areas within a hospital to drive alertness. Maybe you go 4,000K–6,000K in these instances.”
While tunable lighting can benefit a space, sometimes it’s not the best choice. The hours of operation may determine whether having a tunable lighting system even makes sense. If there are different activities at different times in a space, it might be a better candidate for such a lighting control system.
To determine whether tunable white light makes sense for a client and how to apply it, Shell said that Forte makes on-site visits to assess and “discover.”
“We use a human-centered design process that begins with a discovery phase,” he said. “So if it’s an existing space, we take measurements and get occupant feedback prior to a renovation design. We notice shading devices for the sun or bright light, desk and floor lamps, and lamps that have been removed from the overhead luminaire. We try to understand the tasks that occupants have underway and create design solutions that give them the greatest possible control of the lighting for their task.
“There are two types of lighting design: ambient and task. Task is the best place to apply tunable colors. You tune that lighting to the right kelvin. More sophisticated systems might be programmable changing automatically. I’ve seen simpler approaches with a color temperature visualized on a switch allowing you to choose warm or cool color temperature. We are big believers in giving employees control over the lighting. For instance, we are working with PNC Bank so their employees can move to calmer space within the office supported by the correct light spectrum (cooler blue light) when collaboration is needed,” Shell said.
Getting controls right
Craig Casey, senior building science engineer, Lutron Electronics Co. Inc., said at Lightfair that, when working with tunable white light, getting the sequence right with controls is important, especially as you are tuning color temperatures throughout the day.
“Understand what level of personal control will be allowed,” he said. “Is there one owner or several owners of the space? Allow the owners to create the right environment for all the tasks within the space. Write out the scenarios and determine the expected outcomes of the lighting by the owner. Find potential conflicts in the tunable lighting sequence of operation. Finally, if you are in a project pursuing WELL [certification], determine how the tunable light control system can help meet related WELL points in circadian design, color quality, activity-based lighting levels and visual acuity.”
Andrea Wilkerson, lighting research engineer at the Pacific Northwest National Laboratory in Portland, Ore., added that, when commissioning the control system, ensure meters are well calibrated.
“Check the fade rates of the control system so they are smooth and gradual if needed,” she said. “Know what points you are measuring and what you expect in advance to be more efficient and thorough. Remember, surfaces may impact the lighting color of the room.”