Light and Health Video Series

To learn about circadian lighting and your health, check out the new Lighting and Health Video Series from the LIghting Research Center at Rensselaer Polytechnic Institute (RPI) in Troy, NY. Its a step by step explanation about why we need to be mindful about the effect of light on our sleep.

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Beating the winter blues with light

Do you ever think about what you can do to beat the winter blues?  Some “snow birds” head south for the winter, assuming that warmer weather is the solution.   As a not-yet-retired lighting designer and architect living in Vermont, I’m looking for a local, less costly option.  Besides, I like snow!

I know from research being conducted at the University of Vermont Medical Center (UVMC) that Seasonal Affective Disorder (SAD) is prevalent in women but also men during long winters in northern climates.   SAD has been recognized as an official medical diagnosis since the early 1980’s.  This is also roughly the time when special retinal eye cells were discovered that had nothing to do with vision, but were associated with melatonin production and the setting of the body’s circadian clock.   The two topics are related, although there are factors other than exposure to adequate light in determining one’s susceptibility to SAD.

Fortunately, I do not suffer from SAD.  I do, however, recognize a loss of energy and motivation starting around November of every year and ending as the last winter snow banks disappear.  This less severe form of “winter blues” is very common.  Most people are able to cope with it by getting outdoors- whether it is sunny or not- and getting a sufficient amount of exercise.  This does work for me much of the time, but it takes effort when the weather turns nasty. 

Researchers at Renssallaer Polytechnic Institute’s Lighting Research Center (RPI-LRC) are showing how sufficient amounts of artificial lighting can be used to affect a response similar to direct exposure to sunlight.   How much light?  That would be another great blog topic!   Remember, more light alone is not necessarily sufficient to treat SAD, but can be effective in combating the more common effects of reduced winter light.  You may have heard the term “human-centric lighting” to describe designing spaces with the right amount and color of light from morning to night.  The concept is likely going to gain in popularity as these changes are enabled by highly effective (and efficient) LED lighting and control technologies.

The magic of light on a winter’s day- it can chase away the blues if you surround yourself with it.

The magic of light on a winter’s day- it can chase away the blues if you surround yourself with it.

It is certainly the case that the combined daylight and artificial daytime light we get in our homes, places of work and play help affect not only our ability to get a good night’s sleep, but our general outlook during the wintertime as well.   Does this surprise anyone, or does it sound obvious?   

So, can we beat the winter blues with light?   Yep.  My next blog topics will focus on lighting that can help prepare ourselves to avoid next winter’s blues.  The good news is that some options do not involve spending money.   For those who must be indoors much of the time, creative use of existing light sources can be part of the solution.  And, for those who like to be on the cutting edge of technology, we’ll consider the growing options that are already out there.       

If you are in any way connected with K-12 or higher education, I would love to hear from you about lighting in classrooms and academic settings.  Your school could become a case study for combining the best of lighting science and energy efficiency.   Just email me at  

What is Circadian Lighting? Why is it important?

When we adopt good daylighting practices in a building design, we are incorporating circadian lighting.  Circadian lighting, by definition, is ambient light that simulates the color spectrum and intensity of daylight.   Of course, we don’t live in a climate where every day is perfectly sunny.  We also live on a planet where there are many more hours of available daylight in the summer than in the winter, unless you live in the tropics. 

Factoid:  Burlington, VT has an average of 58 sunny days (up to 30% cloud cover) and 101 partly sunny days (40-70% cloud cover during the daytime).   Over the year, we get 49% of the potential available sunshine.

Suffice it to say that circadian lighting in buildings is more important in some climates and parts of the world than others.  Or is it?   Very few buildings have critical access to daylight in every occupied space during the day.  So, anyone who spends a majority of their time indoors is likely not experiencing anything close to circadian lighting unless it is brightly lighted (more than 50 footcandles) with neutral to cool color light in the late morning hours.   Unless you live in a glass house, the amount of natural daylight we experience when indoors is usually not sufficient to provide “circadian stimulus”.

Circadian stimulus.  This is a new metric created by researchers at Renssaellaer Polytechnic Institute (RPI).  It is a calculated measurement that allows us to describe the amount and color characteristics of light needed for effective circadian light exposure in architectural spaces.   It is important to note that effective circadian stimulus can be achieved with either daylight or artificial light, or a combination of the two.  While the quantity and color spectrum of the light is important in terms of circadian stimulus, the timing of exposure is critical.  Late morning exposure to light is critical to regular resetting of circadian cycles.  Late day exposure to bright, cool color light is detrimental to these same cycles.  This has to do with the regulation of the body’s own production or suppression of melatonin.  

Why is melatonin production and circadian stimulus important for human health?  Light is the main stimulus that helps reset the body’s circadian rhythm.  If disruption occurs to this 24-hr cycle, we experience detrimental effects to physiological functions, neurobehavioral performance, and sleep.  This is why we need to pay more attention to not only the kind of light we are using, but also when we are experiencing it. 

An excellent example of daylight and artificial lighting combined for morning circadian stimulus.    Lumenpulse image credit.

An excellent example of daylight and artificial lighting combined for morning circadian stimulus. Lumenpulse image credit.