Color-Correlated Temperature (CCT) is the measurement of the color appearance of a white light source based on its temperature value measured in Kelvin (K). In LED lighting, the common range of color temperatures is from 2700K to 5700K. While all of the color variations in that range are considered white, there is a noticeable difference in color appearance ranging from “warm” white (<3000K) to “cool” white (>5000K). Color temperatures between 3000K and 5000K are referred to as “natural” white.
Warmer color temperatures are typically found in residential environments as well as churches, restaurants, and the occasional office building that prefers a warmer atmosphere. Natural white is most popular in commercial buildings, while cool white is preferred in warehouses and exterior lighting where higher visibility is the main concern.
With legacy lighting technologies like incandescent, high pressure sodium, and metal halide, the CCT was static and could not change within the specific technology. LED lighting, on the other hand, can be designed to emit any specific CCT required for the space it is installed.
New LED lighting technology now offers the ability to change the CCT value on-demand just like you can with dimming. There are many active scientific studies evaluating how the color of light affects your body’s natural circadian rhythm. This new ability now gives building operators the ability to have their interior lighting mimic the phases of the sun (i.e., warmer light in the morning, cooler light in the middle of the day, then warmer light again in the evening). This color-changing helps with attention and focus throughout the day.
This ability to change CCT on-demand is commonly referred to as Tunable White Light (TWL). Studies have focused on three use cases where sizeable potential benefits are possible: schools, hospitals, and office buildings.
With schools and office buildings, the ability to tailor the light to the activity at hand can be very beneficial. For example, higher CCT can assist with focus and attention during tests or presentations while lower color temperature can offer a more relaxing atmosphere for reading, studying, or researching, which can offer a big boost in productivity.
In hospitals, using light to follow a patient’s circadian rhythm in the patient room has shown to expedite the healing process, which is exactly the opposite effect caused by harsh flickering fluorescent lights above and around the patient bed.
For more information on the benefits of tunable white LEDs, check out the U.S. Department of Energy’s Solid-State Lighting Program: https://www.energy.gov/eere/ssl/solid-state-lighting
This article was written by Ricky Arras, LC, and Jason Duncan of Energy Lighting Services (energylightingservices.com). Arras is the Director of Project Development and is Lighting Certified (LC). Duncan is the founder, president, and CEO. If you’d like to talk with a lighting consultant about the lighting in your facility, please call our office at 855.270.3300.