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4 Things to Know about Circadian Lighting

By Kelsey Rowe, PE, CLD

February 3, 2022


Circadian lighting – have you heard of it? Maybe you’ve seen it called human-centric lighting, or you’ve read about how blue light can affect your sleep cycle. The WELL Building Standard features an entire concept on Light, part of which focuses on circadian lighting. You can filter out blue light on your cell phone screen and buy an alarm clock that wakes you up with a happy light.


So what exactly is circadian lighting? And what do you need to know before trying it out for your building or space?

Circadian lighting is lighting designed to have a biological impact on our circadian system. A healthy circadian rhythm has been associated with long-term health and better sleep habits. The goal of circadian lighting is to send signals to our brain, telling our bodies whether it’s day or night, and what functions to perform based on time of day. Many designs are incorporating circadian lighting into new spaces to optimize visual environments, increase productivity and promote the health of building occupants.

Circadian Lighting
Circadian Lighting
Blue Light Wavelength

1. Blue light refers to the wavelength of light.

In general, when scientists or studies are looking at blue light in connection to circadian lighting, they are looking at a certain wavelength of blue light – 460 – 490 nm. Most white LED sources have a peak emission between 400 – 470 nm of blue light. This is different than the color temperature of the light, but many manufacturers promote tunable white or dynamic white LED systems as solutions for human-centric lighting. While changing from warm white to cool white can offer psychological benefits, they aren’t necessarily affecting the circadian system of occupants.

Blue Light Wavelength

2. Blue light isn’t always bad.

Studies have shown that exposure to blue light in the 460 – 490 nm range reduces melatonin production. Melatonin is a hormone your body creates that plays a role in sleep. That means that prolonged exposure to light in this range can shift the normal sleep cycle.

However, additional studies have shown that exposure to this same light can stimulate cognitive functions and increase alertness. Other studies are finding that blue light can be used to treat seasonal affective disorders and other sleep disorders.

Skyline Park Lighting

3. Brighter days, darker nights.

The human body was designed to spend the days in the sunlight and the nights beneath the stars. Our current lifestyle means that most people are not exposed to enough bright daylight during the day, and our nights are filled with too much light. This means that our bodies are not getting the signals they need for healthy circadian rhythms. Studies are showing that the amount of light (think brightness and intensity) have just as big of an impact on our circadian system as the wavelength of the light.

Skyline Park Lighting

4. The internal clock is unpredictable.

You probably won’t be surprised to learn that everyone’s personal circadian system operates a little differently. What may surprise you though, is that your own internal clock and your circadian lighting needs can change on a daily basis. For example, if you got up this morning, drove into the office while it was dark out, and started chugging away at your computer before the sun was up, your exposure to melatonin-reducing light, and your need for it, is much different than your coworker who maybe went for a brisk walk as the sun came up and had a breakfast meeting on the patio of the café downtown.

Van Wert health North Lights
Van Wert health North Lights

The lighting industry is continuously learning more and more about the effects of electric light and daylight on our bodies. There are a number of building standards and best practices that now address how to light spaces with this in mind. This kind of research will continue to shape manufacturing standards as well as energy requirements, and right now it might feel like a moving target. We can help you decipher what options might work to improve the lighting in your space.

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