New Energy Efficient Lighting Reduces Energy Costs

As reported in Consulting Specifiying Magazine

 Energy reduction in existing facilities can easily be achieved by replacing existing inefficient lighting products. Most commercial buildings built prior to 1990 typically are illuminated with T12 fluorescent, incandescent, high-pressure sodium (HPS), or metal halide lamps. These luminaires typically operate on inefficient magnetic ballasts when required by the lamp type. T12 fluorescent lamps are the only one of the four lamps mentioned above that is no longer viable, as they have been replaced with more energy-efficient T8 and T5 lamps.

Both T8 and T5 lamps produce substantially more lumens per W (approximately 100) than the T12 (approximately 60). One other advantage to the T5 and T8 lamps is their physical size. A T12 is 12/8ths of an inch, a T8 is 8/8ths, and a T5 is 5/8ths. There are advantages of this smaller lamp envelope; luminaires can be specifically designed around the lamp, allowing them to more easily control light distribution from the smaller source. This allows the luminaires to be more efficient at delivering the light to where it is intended. Simply replacing T12 fluorescent lamps with T8 or T5 can reduce the lighting load of a building by up to 40%.

Incandescent lamp and halogen lamps are slowly being phased out by energy legislation, but they still have several applications and therefore cannot be considered an antiquated lamp source like the T12. (Editor’s note: Suitable incandescent applications are not discussed here as they are not typically applicable to the majority of commercial buildings.) One location where incandescent is not practical anymore is for general illumination of commercial buildings. Removing incandescent luminaires and replacing them with the energy efficiency of T8, T5, or compact fluorescent lights (CFLs) can reduce consumption and maintenance costs dramatically. A typical 60 W A-lamp screw-in incandescent will produce only about 15 lumens/W versus the 100 noted above for T8 and T5.

In some cases, the incandescent lamps will need to be replaced by CFLs, which are not quite as efficient as linear T8 and T5 lamps but still produce about 60 lumens per W or four times that of an incandescent lamp. Use of LED luminaires also has gained significant steam over the past few years due to millions of dollars of federally funded research and advancement in the technology. LEDs can typically take the place of just about any incandescent lighting application and do it more effectively—and much more efficiently. While the future for LEDs is bright, how they are applied in retrofit applications should be carefully evaluated.

Commercial buildings primarily have metal halide and HPS lamps for large spaces such as lobbies, atriums, warehouses, and parking garages. Currently, both are viable solutions in many settings and can compare favorably to fluorescent in certain applications. One important aspect to consider is that metal halide lamps as they were five years ago (probe-start) are no longer available. Pulse-start metal halide technology improved on the efficiency of metal halide sources dramatically, and legislation such as the Energy Independence and Security Act of 2007 (EISA 2007) has all but outlawed standard metal halide lamps as they cannot meet the more stringent requirements.

Replacing old probe-start metal halide sources with newer pulse-start lamps can reduce energy consumption by up to 25%. To push these savings even further, electronic metal halide ballasts can be used to greatly reduce or eliminate energy loses in the ballast itself. HPS still has applications, but rarely inside commercial buildings due to its very poor color rendering (22 CRI) and warm color temperature (2100 K).

Warehouses, garages, and high-bay areas still have HPS lights. HPS is an efficient light source similar to metal halide but often is not perceived that way due to its “orange” color. When measuring light levels, HPS will produce light levels (measured by a photometer) similar to those of fluorescent and/or metal halide; however, they will not seem as bright. This is due to how the human eye functions at different wavelengths. The light produced by a HPS source is a longer wavelength (approximately 640 nm), which typically will be perceived by the rods in the human eye, and not the cones (which allow us to see color). This is referred to as scotopic vision, or night vision. When cones are not fully functional, such as under HPS lamp sources, objects seem to have no color or appear orange. While photometric measurements will be similar, some suggest that HPS lamp sources should have a reduction factor of up to 25% of this light output due to the poor color rendering and orange color temperature. This issue should be considered when retrofitting HPS spaces.

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