There is a lot of buzz about it, but what you really want is a window.
When the sun rises in the morning, the light has to travel diagonally through the atmosphere. The longer the distance it travels, the redder it gets as the shorter wavelength blue light gets blocked. At noon, when the sun is highest, the most blue light gets through. Then as the day goes on, the light gets redder again as the sun gets lower.
Our bodies have an internal clock that is tuned to these changes in light – the circadian rhythm. For a long time nobody worried much about it, particularly architects and lighting designers. They couldn't do much about it either, because electric lighting was either on or off, and you couldn't change the color.
This has changed; we have electronic controls and we have LEDs that can be mixed to any color. We also have the WELL Standard, "the premier standard for buildings, interior spaces and communities seeking to implement, validate and measure features that support and advance human health and wellness."
The WELL standard takes Circadian Rhythms very seriously:
Light is one of the main drivers of the circadian system, which starts in the brain and regulates physiological rhythms throughout the body’s tissues and organs, affecting hormone levels and the sleep-wake cycle. Circadian rhythms are kept in sync by various cues, including light which the body responds to in a way facilitated by intrinsically photosensitive retinal ganglion cells (ipRGCs): the eyes’ non-image-forming photoreceptors. Through ipRGCs, lights of high frequency and intensity promote alertness, while the lack of this stimulus signals the body to reduce energy expenditure and prepare for rest. The biological effects of light on humans can be measured in Equivalent Melanopic Lux (EML), a proposed alternate metric that is weighted to the ipRGCs instead of to the cones, which is the case with traditional lux.
They didn't teach us about ipRGCs in architecture school; it is all relatively new research. I haven't worried much about circadian-supportive lighting, either; that's what windows are for. You get the view, you get the biophilia from looking at trees, and you get light that changes over the course of the day. But evidently that's not enough.
Over at the Illuminating Engineering Society, Rachel Fitzgerald and Katherine Stekr display a little skepticism in Circadian in the Workplace: Does It Make Sense…Yet?
Lighting designers have had to add “pseudo-biologist” to their repertoire of skills when understanding new research over the past few years. Sure, the profession always required the designer to call upon their inner peacekeeper, artist, psychologist and engineer, but now we’ve added another layer of complexity.
They also note that this is all so new, that there are not really standards yet. "What does circadian lighting look like in practice? Based on what we know today, how do we design a lighting system to support healthy sleep-wake cycles while we wait for more concrete metrics and guidelines?"
Just because we can potentially affect occupants’ sleep-wake cycles with these systems, should we? That’s not to say that these systems should not be used. It’s to suggest that clarity is needed when we are explaining to our clients what these proposed systems are going to do. We are finding there is an intangible component of the perceived color shift throughout the day that simply adds to the value of the space. It’s an ethereal benefit that is hard to quantify, but undoubtedly makes spaces more interesting and appealing to occupants. We know great daylighting design, likely the best form of circadian lighting, promotes healthier workplaces.
I have always wondered why the emphasis isn't on great daylighting design. In Germany, the building code mandates that every worker must have access to a window. Debra Burnet, a daylighting designer, says “daylight is a drug and nature is the dispensing physician.”
Perhaps WELL and the building codes should worry less about the light fixtures and more about the windows. Fitzgerald and Stekr conclude that "tunable, dynamic white lighting might be the wave of the future, and it very well may do all it has been hyped up to do, but we don’t know that yet." But we have known about windows for centuries. Every worker in an office and every child in a classroom should have one.