Light is vital for learning, work, and health, but not too much or too little, and the proper amount and type of light depends on the application.
The Illuminating Engineering Society (IES) recommends a lighting level of 30-50 footcandles (fc) in classrooms. An fc is the light reaching a one square foot surface, rather than overall light emitted in lumens, so represents “working light.”
By contrast, IES recommends 50-200 fc in a manufacturing plant where fine, detail work happens.
In classrooms, sometimes more than 30-50 fc may be helpful. In one study, oral reading fluency of 84 third graders rose 36% using 100 fc “focus” light on reading materials, compared to applying normal light that produced a 17% gain in fluency. (1)
Daylight is an important “free” source, as the light coming in from windows can provide 100-5,000 fc, depending on site orientation, time of year, day, etc. Of course, it’s important to avoid direct sunlight and glare that may impair learning.
Daylight offers advantages per a 2002 study that “examined the role of daylight in student achievement…and found a uniformly positive and statistically significant correlation between the presence of more daylight and better student test scores.” (2)
In a 1999 study of 21,000 students, at one district, students in classrooms with the most daylight performed 20% faster on math and 26% faster on reading when compared to students in classrooms with the least daylight. In Washington and Colorado classrooms with the most daylight, students had 7% to 18% higher test scores than those with the least daylight. (3)
Commonly, schools combine lighting sources for the desired effect, using fluorescent tubes and or LEDs, sometimes managed with control systems to harvest “daylight” and augment it with artificial light for balanced illumination.
The four-foot T8 fluorescent tube is still the most common lamp in the school environment. It’s a 360-degree light source – as it shines in a complete radius around the tube – producing about 3200 lumens (total light output). About half of the light is wasted, emitting only 1600-1800 lumens directionally.
LED lamps provide direct light requiring fewer lumens and less electricity.
Fluorescent T8 one-to-one replacement with 1600-1800 lumen LED lamps is one option. Replacing four T8 fluorescents with two LED tubes @ 2200 lumens each may also work and reduce energy use by 75%.
Choices in LED lighting are making illumination affordable for retrofit or replacement.
Using LED lamps in existing light fixtures or troffers is less costly up front and can be a good interim approach as technology advances.
Conversely, upgrading fixtures to LED troffers provides better control, plus dimming and potentially greater long-term savings.
No matter what lighting choice you are considering, ask vendors for the LM-79 report that, according to the US Department of Energy: “enables objective product comparisons, allows for evaluation relative to performance requirements, and is required by voluntary labeling programs such as … ENERGY STAR®.”
LM-79 data provides electrical, lumen, distribution of light, and color info measured on the Kelvin scale.
Kelvin is a measure of light’s “color”; e.g., 4000K is popular for classrooms and offices, while 5000k popular for industrial settings. A balance between blue and red wavelengths is desired, like natural light. The closer you can get to sunlight’s characteristics, the better.
Also consider the Color Rendering Index (CRI). Sunlight has a CRI of 100. Get as close to that as possible.
There are durable composite coatings consisting of titanium oxide and silver ions that, when applied to light panels and other materials, help control germs with and without light (the titanium oxide kills germs under ordinary light, the silver ions work without light.) These coatings show considerable promise to reduce the spread of infectious agents in the air and on surfaces, while also helping to breakdown VOCs.
Light is connected to health, as light containing a balanced spectrum of light frequency and intensity, aids mood, hormonal function and cognitive performance. (1-4)
The nonprofit National Council on Qualifications for the Lighting Professions (NCQLP) offers an “LC” or “Lighting Certified” credential. Ask an LC lighting consultant for help sorting through the issues.
Manufacturers of leading technologies can also provide expert guidance as they must keep up with the latest advances, know what is working in the field and why.
As researcher Dieter Kunz said: “Fascinating times are ahead … [for] the light industry, clinical chronobiologists, and architects, to mention just a few. By optimizing lighting regimes, we will be able to improve health, save energy, and improve learning and performance.” (5)
Author: Matthew Maa, PhD, Aleddra LED Lighting, www.aleddra.com