Circadian Light Therapy

circadian light therapy

Circadian light therapy is the beneficial use of circadian rhythm LED (Light Emitting Diode) technology. This system mimics natural daylight as it progresses through the day from dusk through dawn, through noon, and to sunset and twilight.

It does this through the modulation of the color and intensity of LED light. This can have a very beneficial therapeutic effect in the right circumstances. However, it is not a substitute for natural lighting

There is a lot of trending buzz about circadian lighting. So let’s dig into what it all means.

Our circadian rhythm

The term “circadian” is relatively new. It was coined by scientist Franz Halberg in 1959.  According to Halberg the word derives from the Latin “circa” (meaning about) and dies (meaning day). 

However, the idea that humans and other things in nature respond to the light cycle of the day is ancient and you will find some fascinating information here.

The term is now mostly associated with “Circadian Rhythm.” This is associated with the cycle of 24-hours that is inherent in our various biological processes. These include sleep, wakefulness, and digestion. You can get the idea from the image above.

This circadian phenomenon also influences our overall physical performance, alertness, blood pressure, body temperature, hormone levels, sleep, and metabolism. It affects us on many levels and these include our immune system.

The word even gave rise to the term “circadian dysrhythmia” or disruption to the body’s natural clock. This would include jet-lag arising from travel across multiple time zones.

Here is a nice explainer video:

How natural daylight changes

Since our focus here is on circadian lighting specifically, and how that can affect us. Let’s see how natural daylight changes with the passage of the day.

The sun moves across the sky. And as it moves, the atmosphere filters the sunlight in different ways. When the sun is low in the sky in the early morning and late afternoon, its light must penetrate through greater distances in the atmosphere than when the sun is right overhead at midday.

In our school physics classes,  we learned that sunlight arrives in a spectrum of light waves ranging from infrared to ultraviolet. The further sunlight has to travel through the atmosphere, as is the case in the early morning and late afternoon, the more the shorter wave blue light is scattered and in effect blocked.

circadian light therapy

This is why the sun appears to be redder early in the day and late in the day. But when the sun is directly overhead, with the minimum atmosphere to penetrate, the full-color spectrum, including blue light, comes through strongly.

These changes in light during the day are what our circadian systems are designed to expect and it’s what they need. At the start of the day, we want to be gently woken by a red-shifted light. And in the middle of the day, we want the stimulation of strong blue-shifted light. And then at the end of the day, we want to be gently soothed by a red light.  

Our circadian light problem

Here is our problem with circadian light and our circadian rhythm. We spend so much of our time indoors that we have come to rely heavily on artificial light. And, until the arrival on the scene of circadian lighting systems, this type of artificial electric light was in a constant state. In other words, it did not and could not change color during the day in the same way as natural sunlight. 

This is not good for us. Scientists have found that an unchanging artificial light can have an adverse effect on our circadian clock. In turn, this has an adverse effect on the psychological and biological functions associated with our circadian rhythm.

This is easily understood when you compare a sunny day with a cloudy day. A sunny day is a natural mood booster. And a cloudy day can make us feel gloomy.

The solution to our circadian light problem

The solution is twofold. The best, most obvious and effective solution is to bring more natural light into our homes and workplaces. The Europeans are ahead of us in this. In fact the Germans actually mandate minimum levels of daylight in workspaces.

The second part of the solution is the use of supplementary circadian lighting in enclosed spaces, where there is no or insufficient natural daylight.

How do you get more natural light into the home?

There are many ways to bring more daylight into the home. This can either amplify what you already have or it can bring it into spaces that have never seen natural light. 

Taken together, they all have a cumulative effect. And by the way, as a former builder and remodeling contractor, I know quite a lot about this at a practical level. So you can rely on this information.

21 ways to bring more natural light into the home

1: Put in solar tubes. These are great for bathrooms and other smaller spaces, where a skylight is too large. A system of lenses and polished stainless steel transmits sunlight through the roof and sheds an exceptionally bright light within the room.

solar tube

2: Put in skylights. These are a better option than solar tubes in larger rooms, although much more expensive, mainly because of the added cost of installation.

3: Install more windows or enlarge existing windows.

4: Exterior glass doors. It may be feasible to add glass patio sliding doors to access the yard.

5: Clean windows. Make sure your windows are kept clean.

6: Glass block walls. Install glass block walls in exterior and interior walls as appropriate. As you can see here, this can also add a decorative splash

glass block wall

7: Trim back trees or shrubs that may be obstructing light from the windows.

8: Put in light colored flooring for its reflective effect

9: Paint walls and ceilings in light colors. As a general rule,the ceiling should be white. Use a gloss or, at least a high sheen finish.

10: Make sure the paint of your window trim is whilte. This creates the illusion of a larger window and helps reflect light around the room.

11: Paint the roof eaves white. This will help reflect light through the windows.

12 Replace solid exterior doors with glass. Or at least add a glass panel. You can do this in the door itself or (if there is room) down the sides of the door.

circadian light therapy

13: Glass interior doors: Whenever feasible or appropriate, use glass interior doors or panels (frost them for privacy, if needed).

14: Window drapes. Get rid of heavy window drapes. Use translucent fabrics.

15: Install mirrors. These reflect light around the home. Where possible, place mirrors opposite each other.

16: Use glass or reflective tiles in kitchen and bathroom backsplashes.

17: Use other decorative reflective materials to bounce the light around. You might include glass objects.

18: Include a water feature. A fish tank or fountain will add reflective surfaces.

19: Move furniture away from the windows to avoid obstructing light.

20: Use light colored furniture.

21: When designing a remodeling project, try to remove partition walls where this makes sense. This not only lets a great deal more light around the home. It can also improve its functionality.

And, by the way, many of these measures will add value to the home..

Use circadian lighting systems

Natural lighting is best. But circadian lighting systems are a great way to supplement it when necessary, especially in enclosed spaces.

Until recently, this was not possible. You had an electric light that was either turned on or turned off. Of course, we had dimmers that could turn the light intensity down, but there was no way of controlling the color of the light that was emitted.

But now that we have advanced LED lighting, we are able to modulate, manage, and mix luminescence and light colors in such a way that we can imitate circadian light. In other words, in the absence of natural light, we are able to provide what our circadian rhythm needs.

These LED circadian systems can give us warm, red-shifted light at the beginning and end of the day, and a brighter more stimulating blue-shifted light in the middle of the day. This is an artificial way of providing a timed circadian sunrise-to-sunset effect.

Getting a little technical

In techno-speak, the LED circadian lighting system moves through the color spectrum. This is from a dimmer, warmer 2700K through a brighter and cooler 6500K in the middle of the day, and back again to the dimmer, warmer 2700K at the end of the day.

Lighting language

Lumen: this is the brightness of the bulb

Wattage: this is the amount of energy consumed in the  production of the light (with LEDs it is much less than with the classic incandescent bulb)

Kelvin (K): this is the color temperature of the light measured on the Kelvin absolute scale of temperature. 

It is the Kelvin value that is important to the circadian lighting system. A “soft white,” which is what we want in the morning and late afternoon hours, has a lower Kelvin of around 2700K to 3000K.

A “bright white” is at around 4000K. And a “daylight/full-spectrum” light, which is what we want in the middle of the day, comes in at 5000K+. This produces a cool, bluish tone of white. 

However, be aware that some people with vision issues may find anything above 5500K glaring and uncomfortable.

Westinghouse has provided these handy graphics. These are not directly related to circadian lighting systems but help us understand Kelvin and its effect on the light we see.

kelvin table
kelvin color temperature effect

What makes circadian lighting systems so effective is that they are able to change the Kelvin temperature of individual LED light bulbs during the day.

Commercial circadian lighting systems 

Some commercial environments benefit from circadian rhythm lighting. It has been found that circadian lighting is helpful in managing the sundowner syndrome in Alzheimer’s patients. So Watermark Retirement Communities has installed these systems in some of their properties. This is a great illustration and application of circadian light therapy.

NASA is also looking at circadian lighting for space stations. Astronauts in orbit can experience 16 sunsets per day! And you can imagine this wreaking havoc on the circadian clock and causing all kinds of unnecessary stress that stand to get alleviated in this way.

Home-based circadian lighting systems

We can now use circadian lighting systems in the home in order to supplement the natural light we are bringing in. And of course, in some areas of the home, there is no natural light to be had at all. So this type of lighting is perfect for basements, for example.

What are our circadian lighting options?

This is still an emerging technology, so it does not make sense to go totally all in for it right now. But it is definitely worth trying out. This would be especially the case in basements, where there is virtually no possibility of bringing in natural light.

As for cost, this is negligible compared to the high cost of some of the ways of bringing in natural light, like installing skylights or glass block walls. SO try out this circadian lighting system by  Philips.

This is Alexa and smartphone compatible. There’s a nice explanation here.

Conclusion on circadian light therapy.

In our world of natural health and healing, it’s hard to think of a better way to get the natural rhythms of nature back into our lives than by paying attention to the importance of natural light.

Our bodies and minds were developed over eons in an environment of natural light. So the more we bring it into our homes the better we will feel, whether we do this naturally or artificially.

Here at, we are strong advocates for the natural way of doing things. But we are also down-to-earth practical people. And we are not hostile to science. So, when our efforts to bring in and enhance natural light reach limits, we embrace a technology that will emulate it and help us get to where we want to be. 

The new circadian lighting technology is an important advancement and we should take advantage of it. Many of the rooms in our homes have zero natural light. Think basements and some bathrooms and interior rooms. 

These are perfect candidates for a circadian lighting system when you compare it to the cost of the natural light alternatives we talked about earlier. Besides, our living rooms and bedrooms can also benefit from morning and evening illumination by supplemental, soothing red-shifted lighting, rather than the harsh white lighting we are used to.

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