Daylight and Health

a guest post by Lisa J. Reed, Lighting Designer

There is no denying the importance of daylight and its impact on people.

The sun has come out, the snow has melted, and the spring has finally arrived in Missouri. There is no denying the importance of daylight and its impact on people. Parks throughout our region have been crowded with children and parents, cyclists and skaters, walkers and joggers basking in the warm rays.

People are phototropically inclined, in other words: drawn to light. Instinctively we know this to be true, but is there evidence? If so, how can we incorporate this knowledge into building designs?


Research abounds about daylight and health. Exposure to light from the sun is good for circadian rhythms, decreases seasonal affective disorder (SAD), helps jaundiced and premature babies with faster recoveries, and improves the sleep patterns of dementia patients.

The impact of daylight leads us to other important questions about the impact of electric light on people. Blue wavelength light at night suppresses melatonin production (and melatonin is thought to be a cancer suppressor), so there are links to nighttime light exposure and certain types of cancer. Computer screens and other electronic devices emit light from the blue end of the visible spectrum, so it is important to be cautious about using these devices late into the night. Researchers are especially concerned about how these devices disrupt children’s sleep.


Research is overwhelmingly consistent that quality daylighting in the classroom results in improved student test scores.


Have you noticed more windows or skylights where you shop? Studies indicate that retail sales increase in spaces with natural light, but some high-end shops in New York are opting for windows simply because “it enhances the product and provides a breath of light for sales associates and customers.”


Multiple studies have shown that office workers with outside views are more productive. There are even LEED points for structures that provide views to 90% of workers.

The truth is, productivity increases alone can more than offset any costs associated with improving daylight in most facilities. But you do even better by using your daylight to save energy too. Use daylight harvesting tools such as photocells (light sensors) combined with dimming to reduce electric consumption when the sun is providing free illumination.

You may want to consider installing automatic mechanical shades for glare control

One of the challenges of daylight is that it can create glare. You may want to consider installing automatic mechanical shades for glare control (pictured above). These can be connected to building management systems and programmed to open and close at optimum times. This keeps things looking clean and uniform - with all shades at the same height – in contrast with manual shades which can be up, down, or in-between.

Are you getting the most out of daylight in your space? What changes would you like to make today?


Lisa J Reed photo - Lighting Blog

Lisa J. Reed has been attracted to lighting (like a moth to a flame) for 20+ years. She is the Founding Principal at Envision Lighting Design, LLC in St. Louis, where she designs, teaches, and writes about architectural lighting.


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