All lighting sources are not created equal, and simply providing the proper lighting level in a space is not always enough. Quality of light, efficacy, lamp cost (initial, replacement and life cycle) and environmental impacts are all key factors to consider when choosing the appropriate lighting source for a specific application. A proper lighting source helps to define a space, creates ambience, supports way finding and can even help improve patient diagnosis, treatment and therapy. In addition, the right lighting source can even save money by increasing employee productivity as well as decreasing maintenance costs and energy usage.
Quality of Light
Quality of light can be a critical factor in choosing the appropriate light source to use. The color temperature and the color rendering index (CRI) of a light source affects the way a space is perceived; in particular, the way that people, colors and objects appear. For most, the ideal lighting source would be as close to the equivalent of natural sunlight as possible, which is a 5,000 Kelvin temperature (K) rating. Incandescent lamps provide the closest lighting to natural daylight, whereas HID lamps provide the poorest quality of these four light sources. Compact fluorescent and LEDs fall in between with color temperatures ranging from 2,700 K to 4,100 K. Depending on the function of a space, the ability to accurately distinguish among colors is essential. While the ability to identify whether a label on a box is red or blue may not be critical for everyone, for a doctor or surgeon, proper color rendering is essential for accurate patient diagnosis and treatment. Incandescent lighting provides the best color rendering of all the light sources being analyzed with a perfect rating of100 out of 100. Although they are not as good as incandescents, compact fluorescent and LED light sources have a CRI in the low 80s. Some of the newer HID sources have a CRI close to 80 but most are in the 20s or lower, making the HID a poor choice for color accuracy.
Cost and Life Span
One of the main benefits of incandescent lamps is the comparatively low initial cost. Other lamp choices providing the same equivalent light output can cost more than four times as much as an incandescent lamp. Of these, LED lamps are the most expensive. Also, an incandescent lamp has only an average rated life of approximately 1,000 hours; compact fluorescent lamps have an average life span between 6,000 and 12,000 hours; HIDs range between 10,000 to 30,000 hours and LEDs last 50,000 or more hours. Although incandescent lamps are cheaper per unit, its life span is also significantly shorter. Therefore, it is important to consider factors in addition to lamp replacement costs such as man hours and equipment required to perform lamp replacement such as a ladder, power lift and scaffolding.
The efficacy with which different light sources are able to generate usable light from the amount of energy used affects the amount of electricity required to light a specific area. Incandescent lamps provide only approximately 12-15 lumens per watt (lpw); only 7.5 percent of the energy used by an incandescent lamp is actually converted into usable light. The remaining energy transforms to radiated heat and light output in frequencies invisible to the human eye. Unlike incandescent lamps, compact fluorescent lamps provide at least 50 lpw1; LEDs provide 30-35 lpw1, and HID lamps provide close to 90 lpw. Therefore, a compact fluorescent lamp providing the same approximate light output as an incandescent lamp uses about one quarter to one third the amount of energy that an incandescent lamp uses. Each year, LED technology continues to improve. Presently, however, the light source from an LED is bright, but narrow in the direction you point it; therefore, LED’s are best used as task-specific lighting such as reading lights, night lights and signage lights and may not be best-suited for general overhead lighting.
Two significant environmental concerns associated with lighting choices include energy consumption and the disposal of lamps containing mercury-a hazardous element that can cause significant damage to our water systems if not disposed of properly.
The Energy Independence and Security Act, passed by Congress in June, 2007 requires lamps to be 25 percent more efficient by 2012. This act will ban the manufacturing and sale of some incandescent lamps because of their inefficiencies. Improving the efficiency of lighting sources will ultimately decrease the quantity of power required to be generated by our power plants and thus reduce the level of carbon dioxide emissions created by them.
Compact fluorescent and HID lamps use small quantities of mercury inside their glass housing. Because mercury is a hazardous substance, the Environmental Protection Agency requires proper disposal of broken or used lamps. This regulation is essential for preventing mercury contamination of landfills, incinerator ash and water streams. LEDs do not contain mercury; and therefore, do not require special disposal methods.
It is important to understand the short and long-term benefits of your lighting choices and how they function before choosing the right one for your facility; as the best lighting source for one use may not be the best for another. You should consider key factors such as quality of light, efficacy, lamp cost and environmental impacts when choosing the lighting source for a given area or application.
For more information on lighting sources, proper lighting selection or other questions regarding MEP systems, please contact Jonathan Slagel, PE at (717) 845-7654 or firstname.lastname@example.org.