“Warm white” and “Cool white” have been standard colors of fluorescent lighting for decades. The maturation of LED light sources now give us many more choices in the colors of light we use in buildings. Some fixtures allow the occupants to manually select the color they want and the use of wall-washing or ceiling-washing fixtures allow visible color of the surface to be changed by turning a dial or slicing a switch. Other fixtures allow the light color to automatically change with the time of day to align the interior light sources to mimic the changes in natural light that occur from sunrise to sunset. It is thought that these subtle changes of color help the human body to wake up and prepare for sleep. Therefore, replicating them in artificial indoor light sources may also assist the occupants’ sleep patterns. Circadian light sources were provided to replace the previous fluorescent lighting fixtures on the International Space Station in 2017 in an effort to aid astronauts sleep patterns, which was a significant issue. For more information on the study of circadian lighting on the International Space Station click here.
Color temperature is measured on the Kelvin system of measure as degrees Kelvin. Cool white is typically around 7,000K and warm white in in the 3,000K range as shown in the graphic below. This illustration is available if you click here.