If only circadian lighting was as simple as its most often made to be. All you need is to clamp down on lighting intensity and color temperature controls and everything’s good. Right? Unfortunately, circadian lighting (human-centric lighting, daylighting, etc.) is a lot more complex. “True circadian lighting,” according to veteran lighting designer Alessio Urso, “Depends on so many external factors that are very difficult to control.”
Using Lights to Train Our Circadian Rhythm
Lights are just a portion of the puzzle when it comes to circadian rhythm, but it’s a good place to start. The rhythms are largely influenced by the traditional 24-hour day and night cycle that’s been going on since humans first started to walk the earth. You can imagine, then, that it’s a pretty deeply ingrained cycle. At the start, though, we were outside nearly 100% of the time. Now, we spend 90% of our time indoors in front of blue-lit screens (blue being the color that often tells the brain it needs to be awake for daytime).
Integrators are all brushing up on the subject, and manufacturers have made tremendous strides in making easy-to-install, affordable human-centric lighting (HCL) systems, but there’s no replacing a lighting designer for developing the most effective set-up for a home.
Urso states there are a number of factors that decide how well we can train ourselves so that we stay on the same track evolution set up for us. Lighting intensity and color temperature are two, as we mentioned earlier, but others less commonly talked about include:
- Timing (when the transitions occur)
- Light history (how light presents itself in an individual’s context)
- Spatial distribution (how intense lighting distribution is and where it comes from)
- Spectrum (like color temperature, but more focused on non-visual wavelengths like ultraviolet)
Not All Circadian Lighting Is Built Equal
As Urso says, “Light color temperature can be shifted from warm to cool, and back to warm throughout the day,” Urso says, “but that will not help much if the spectrum is not appropriate.”
Each 5000 Kelvin fixture has the potential to behave differently due in part to their varying spectral output, better displayed by their color rendering index (CRI) score. CRIs above 95 come closer to natural daylight, which by definition registers at 100.
Knowing this is just the beginning, according to Urso. An effective scheme should utilize both direct and indirect lighting, wall sconces, floor lamps, windows (i.e. shading control and photsensors) and more. It falls back to spatial distribution. Not only can it play a strong role in triggering circadian response, but it also provides tremendous visual comfort.
Providing Circadian Lighting the Way Only the Sun Can
“Lighting coming from above the horizon is best in the morning,” Urso says, “but typical downlights are not effective because our brow bone blocks most of the light that needs to go into the eye.” Anywhere from zero to 45 degrees above the horizon is actually the best spot for morning lighting. There, the light strikes photoreceptive cells in the retina that are responsible for the creation of melatonin, the body’s natural sleep aid.
It goes without saying, then, that effective evening scenes need the light to come from below the horizon, employing table lamps, step lights and other lower-level illumination wherever possible.
We should look no further than human evolution and the history of the world to recognize that our DNA revolves around the rising of the sun before the work day and the setting of the sun at bedtime.
And yet, can you remember the last building you stepped into, residential or otherwise, that employed this assortment of fixtures at varying levels to support these natural cycles?
“For circadian lighting to be most effective, it has to be coordinated between the lighting designer, interior designer, architect, and controls specialist,” Urso says.
Another version of this article previously appeared in CE Pro.