How does my home's lighting influence my health?

Lighting has important psychological effects on us as human beings, from when we wake up til the time we go to bed.  Examining the three characteristics of light, brightness, saturation and hue, helps to better understand what is going on. 

Brightness  (scientifically called luminance) is important when you think of the many different workspaces you have around the house.  The kitchen needs adequate illumination, as does the bathroom, stairwells, and any office or study space.  We want brightness for good productivity and energy.  

Brightness does not have one simple measurement!  Illuminance is the amount of light falling on a surface, which is what we need for task lighting.  It is measured in lux, and is affected by the brightness of the bulb (measured in lumens), the angle (for LEDs) and distance to the surface you’re measuring.  These are a lot more factors than the typical light bulb package reveals!  For example, we are used to describing light bulbs in watts (the power used), which did give an idea of brightness for incandescent bulbs, but in the advent of CFL and LED lighting, watts don’t adequately describe brightness.  It would be more helpful to understand the bulb brightness in terms of lumens (the scientific way of measuring its brightness), which is how bright the bulb actually is.  Fortunately, package labeling has changed to include this information. 

This label is from the website, which also gives guidelines for replacing bulbs.  Since energy-saving bulbs use fewer watts, we can replace a 100 watt incandescent bulb with a 1600 lumens bulb, a 75 watt incandescent bulb with 1100 lumens bulb, 60 watt incandescent bulb with 800 lumens bulb, and 40 watt incandescent bulb with 450 lumen bulb.   The label, then, corresponds to the brightness of a 60 watt incandescent bulb, but since it uses only 13 watts, we know that it is not incandescent.

The other factors that affect brightness are the distance (and beam angle of light hitting your surface, if it’s an LED light).  More distance and greater angle means more diffused light (less light you will see at the surface).  Lux is the measured light we see at a surface.  For example, 500 lux minimum is recommended for studying.   If you only have overhead lighting and it doesn’t seem to be bright enough, you can use this online calculator tool to convert lux to lumens to see what bulb you will need, or add a desk light to amp up the lux.   When redesigning a space with recessed lighting, you can use a calculator that incorporates the ceiling height and room dimensions to get the number and spacing of overhead lights to provide general lighting, and add task lighting such as lamps wherever more light is needed (like next to a recliner for reading).  Since many more of us are working from home at least part-time now, it's super- important not only to make it comfortable and healthy.  Adequate lighting is a big player in transforming a part of your home to a healthy office.

Hue: This is the color of lighting, which as I said in the post about “Why wear my sunglasses at night?” is extremely important.  Cooler lights (blue tones) energize us, while warmer lights (think amber and red tones) increase melatonin production to help us get sleepy.  There is even a correlation between green light and healing; green colors were introduced in hospitals in the 1930s to increase patients’ mood of growth and recovery.  Surgeons use different color lighting to their advantage to reduce eye strain, stress and perform better, so why not use them in our homes?  Philips Hue is a smart lighting system that uses the connectivity of wifi to change the color and brightness of your lamps to invoke different moods or times of day, as well as turn lighting on and off remotely.  This is quite tempting, especially after reading a testimonial that by turning off white lights and turning on amber lights, kids were able to go to sleep faster.  Also, you can set the “mood” of your living space simply by saying a command or changing it through the app.  However, the availability of the blue light in these LEDs is concerning for homes with children and teenagers, because their eyes are not able to fully filter blue light and are more sensitive to cold blue light, according to a French environmental authority report.  For a healthy home and not just entertainment value, ideally smart bulbs would be programmed to change from blue-green in the morning (to waken us) and red or amber in the evening to get us ready for bed.

Are there good uses for blue light?  Yes, for sure–in 2009, Tokyo installed blue lights at the ends of their Yamanote railway line, and suicides decreased by 84% where the lights were changed.  Gatwick Airport made the same lighting changes to their tram lines.  Unfortunately, scientific evidence has not found that blue lights decrease impulsivity, so it may be a case of new lighting causing people to be more self-aware.  Maybe refrigerators should be equipped with blue lighting to combat those cravings to munch(!).