This article was originally published in the November/December 1994 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.
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Home Energy Magazine Online November/December 1994
Lighting Makeovers: The Best Is Not Always the Brightest
With a wide range of energy-efficient lighting designs to choose from, quality of light and quality of life go hand in hand with energy savings.
by Kathryn M. Conway
Kathryn M. Conway is the editor-in-chief at the Lighting Research Center at Rensselaer Polytechnic Institute in Troy, New York. She co-authored The Lighting Pattern Book for Homes from which this article is adapted.
As new and improved energy-efficient lighting technologies appear on the market, creative choices for designing home lighting have never been greater. It's now possible to enhance the quality of lighting throughout the entire home while cutting energy costs dramatically. And, surprisingly, this achievement does not come merely by substituting the latest compact fluorescent lamp (CFL) for the familiar incandescent A-lamp.
Assuming that we strive to use daylight when and wherever possible, we can save electric lighting energy in two ways: by reducing the amount of power required by the lighting system or by reducing the amount of time that the lighting system operates. Input power is measured in watts, time in hours, and the energy that is consumed in watt-hours.
Input Power X Time = Energy
Keeping this simple equation in mind helps us choose technologies that balance our need for light with our energy and financial resources.
Lamps, luminaires, ballasts and some lighting controls require energy to operate. The materials, design, and method of operation of each of these technologies has a significant impact on how much energy they consume, so specifiers need up-to-date technical information to make good choices.
Rated lamp wattages are listed on packaging materials and are often stamped on the lamp itself. Actual wattages for lighting systems that use fluorescent or high-intensity discharge lamps will vary from the listed wattage, however, due to the additional watts that are consumed by the ballast. Low-voltage lamps also require slightly greater wattage than that stated on the lamp or package, due to transformer losses.
A phrase from the vocabulary of desktop publishing, What you see is what you get applies to lamps, too. We need to know what we will be able to see when we use a lamp, and this depends not only on the wattage of the lamp, but also on its design and material construction.
One measure of what we get when we buy a lamp is efficacy. The amount of light that emanates from a lamp is measured in lumens. Some lamps produce more lumens per watt than other lamps. High-efficacy lamps consume less energy than low-efficacy lamps of comparable light output. You can use efficacy, described as lumens per watt, to identify lamps that more effectively convert the energy you pay for into light. If the packaging lists the average rated watts and the lumens, then divide the lumens by the watts to determine the efficacy.
Another measure of what we get in a lamp is embodied in the shape and intensity of the pattern of light it distributes. This is influenced by the shape of the light bulb itself and any reflective coatings that are applied to the bulb. The light distribution pattern is a very important consideration for energy efficiency, because it enables the user to direct light to the area where it is most needed.
Color is an important aspect of what we get, too, and it has two measures: color rendering index, CRI (on a scale up to 100; the higher the number, the more accurately colors are rendered), and correlated color temperature, CCT (on the Kelvin scale; the lower the number, the warmer or more yellow is the color, the higher the number, the cooler or more blue is the color). Standard incandescent lamps have a CRI of 95+ and a CCT of 2,800. Fluorescent lamps come in many combinations of CRI and CCT. The types of phosphors that coat the inside of fluorescent lamps determine their color characteristics.
When we select a lamp, we need to consider efficacy, light distribution, and color, and find the optimal combination for the task. For example, if a resident wants to highlight an oil painting in the living room occasionally, color and distribution of light will be more important than efficacy. Thus, a PAR 38 halogen flood lamp will probably be a better choice than a CFL, due to its superior color rendering and even, directional light distribution, even though its efficacy is far lower than the CFL's.
One relatively new lamp technology that most consumers seem well aware of is the halogen lamp. What many people do not understand, though, is that halogen lamps are incandescent lamps, and they are not necessarily efficacious, nor will their use save a great deal of energy (see Table 1). They are probably popular because they deliver what many people describe as bright white light. Indeed, they do produce more lumens per watt than a standard A-lamp, and their CCT is 3,050. But some electric utility program managers suspect that the low price and great popularity of halogen reading lamps, table lamps, and the ubiquitous discount store $29.99 halogen torchiere may well counteract the energy benefits that they labor to gain through CFL rebate programs. When a resident operates several torchieres, energy use is likely to increase because each of these tubular halogen lamps requires 300 or 500 watts to operate. The only mitigating factor is the manual dimmer that is featured on many models, which may encourage the resident to lower the light level and thus the energy consumption.
The halogen lamps that do help to save energy are the replacements for standard A lamps and reflector lamps. An even more efficacious type of lamp combines the halogen technology with an infrared-reflecting (IR) coating on the inside of a capsule within the lamp bulb. Until recently, IR lamps were available only to the commercial sector. With the passage of the Energy Policy Act of 1992, however, many more will be introduced to the residential market.
Metal Halide Lamps
This is another lamp technology that was developed for the commercial market but will be applied more frequently in residences as manufacturers continue to improve the color characteristics and engineer smaller products in appropriate wattages. Metal halide lamps combined with fiber optic systems promise exciting aesthetic options for homes and should be useful for lighting hard-to-reach areas. Some manufacturers and designers are experimenting with single, powerful lamps whose light could be distributed to many locations via fiber optics and light pipes, potentially removing the need for many individual lamps scattered throughout the home.
Linear Fluorescent Lamps.
Note from Table 1 that all incandescent lamps have far lower efficacies than do fluorescent lamps. Linear fluorescent lamps are economical, long-lasting, and when combined with electronic ballasts, make an excellent alternative to incandescent lamps for many areas of the home. Manufacturers are introducing new linear fluorescent lamps with color qualities suitable for homes. Residents who associate the word fluorescent with yucky color should be pleasantly surprised by these improvements. Retailers, utilities and specifiers should make an effort to demonstrate the new technologies to help overcome these perceptions. Linear lamps come in many lengths including subminiatures that will fit in very small spaces; these are likely to be incorporated into new luminaire designs.
Compact Fluorescent Lamps
While not quite as efficient as their linear counterparts, compact fluorescent lamps far outshine incandescents in lumens per watt and in longevity. In the past few years technological advancements in CFLs have meant a greater choice of sizes, shapes, and lumen output, and consequently a wider variety of applications for the home. Screwbase compact and circline fluorescents can fit directly into medium-base lamp sockets. They are usually heavier and larger than the incandescents they replace, so size and stability need to be considered. In certain fixtures it may be necessary to install a socket extender or harp extender to accommodate the CFL. Dedicated, pin-based CFL fixtures eliminate this problem and insure that incandescents will not be used as replacements. CFLs that work with dimmers or three-way switches are still being perfected. Outdoor use of compact fluorescents is limited to regions with temperate climates. CFLs are nondirectional light sources; some are available with diffuser capsules and others come with reflectors for a more directional light. Although CFLs have broad application, they perform most economically when left on for three hours or more and should not be considered for lights that are switched on and off frequently.
A new type of lamp, referred to as electrode-less or induction, offers many of the advantages of fluorescent lamps, especially high efficacy and good color quality. Some are appropriate for replacing incandescent reflector lamps and others for standard lamps, for both indoor and outdoor use (see Whatever Happened to the E-Lamp?, p.45)
Fluorescent, metal halide, and electrode-less lamps require a ballast or other electronic device to operate. Many people's negative reactions to fluorescent lamps likely stems from their experiences with fluorescent lighting systems operated by old or poor-quality magnetic ballasts that hum or buzz. These magnetic ballasts also operate lamps at a low frequency that some people can detect as flicker, which may give them headaches. These problems can be avoided by using electronic ballasts, which operate at a much higher frequency. Dimmable electronic ballasts should have great appeal to residents; however, at this time their cost is prohibitive for many applications. One of the most frequent comments from visitors to the Lighting Research Center's residential demonstration is, Wow, I didn't know you could dim fluorescent lights ... that valance looks great! (The valance has both an uplighting and downlighting component, each controlled by a dimmable electronic ballast that operates 48 fluorescent lamps.)
Luminaires have several functions: they provide the physical support for the wiring, ballast, and lamp; shield the lamp from the occupant's direct view; and most importantly for energy concerns, they direct light to where it is needed. The efficiency of a luminaire depends upon how well it is designed to reflect light out of the luminaire itself and in a distribution pattern that is appropriate for the overall lighting design. Thus a good match between luminaire and lamp is essential. Placing an A shape lamp in a recessed can that was designed for a reflector lamp wastes energy by not directing the light out of the luminaire.
The residential lighting market is slowly beginning to carry luminaires that are dedicated to fluorescent lamps of various shapes and sizes. Many efficient luminaires are now available for vanity areas and kitchens. Better-quality and more attractive luminaires containing small-diameter linear lamps are also available for under and above cabinets. The Lighting Pattern Book for Homes encourages specifiers and manufacturers to create economical lighting systems that feature soffits, valances and coves containing linear fluorescent lamps and electronic ballasts. These luminaires can be built easily on-site, or pre-assembled units can be installed and then painted or covered with fabric to match the home's decor. Consumer and advocacy groups could have a significant impact on the lighting industry if they demanded more choices in energy-efficient luminaires.
Intuitively, we expect that the more a room is used, the more the lighting in that room will be used. Of course, we all know that the lights stay on unless they are turned off, and that people may forget to turn lights off when they are not needed. Energy-conserving habits should include using daylight when it is available, dimming lights when lower light levels are acceptable, and turning lights off whenever they are not needed. Lighting controls that are easily accessible enable residents to make the best use of a lighting design and conserve energy. For example, you can install three-way switches to control lighting in areas that have more than one exit, such as hallways, staircases, and large rooms. You also should consider adaptive techniques or devices such as glow-in-the-dark switches, switch plates of high-contrast colors and oversize toggles. The mounting heights for wall switches established by the Americans with Disabilities Act can make lighting easier to control for anyone!
In some areas of the home, automatic controls can supplement or substitute for manual controls. Going back to the equation at the beginning of this article, we can see how controls have the highest potential for saving energy in areas where many incandescent lamps, or several high-wattage incandescent lamps, are installed, because reduced operating time can help compensate for the high wattage. Although homes do vary significantly, it is reasonable to assume the following average hours of use per day: four hours for a kitchen that is used for both food preparation and dining; three hours for a kitchen dining area or food preparation area, and living or family room; two hours for a bathroom; and one hour for a bedroom.
Specifiers and contractors should take care to choose controls that are compatible with lamp and ballast technologies, and also should try to procure the best quality that is available, perhaps choosing a commercial grade rather than a residential grade product if heavy use is anticipated. Many negative experiences concerning controls arise from misapplications of the technologies or from poor-quality products that fail to perform well over time.
Dimmers can save energy when they are used by the resident to lower the light output of lamps. They are very popular for dining, living, and family rooms and large kitchens. They are available for incandescent lamps, including low-voltage systems, and for many fluorescent lamps. For the latter, the dimmer must be combined with a dimmable ballast. Wherever many high-wattage incandescent lamps are controlled at one point, consider adding a hard-wired dimmer. Dimming incandescent lamps should extend their life; however, if tungsten halogen lamps are dimmed frequently, manufacturers advise operating them occasionally at full light output.
Timers turn lamps off after a designated time period. Some operate like a clock, to turn lights on and off at specified times of day and night; these are useful for security applications and special needs, such as plant lighting. Interval timers turn lights off after a period of minutes or hours, and are a lower-cost alternative to motion detectors. Both mechanical and solid-state interval timers are available, and some offer the option of a manual override. Avoid using interval timers in rooms where the resident could be stranded away from the switch when the lights turn off or at least add a simple, very low-wattage night-light with a photosensor near the switch to serve as a beacon.
Plug-located and socket-located timers and dimmers are also available. These are useful for residents who want to fine-tune control of table and floor lamps within the home. For example, microchip electronics combined with standard A-lamps offer residents a new line of low-cost and easy-to-install products.
Motion detectors are often called occupancy sensors; they automatically turn lamps on when motion is detected, then off after a specified period of no motion. Some new models feature manual-on/automatic-off switches, which avoids the problem of false-on operation. Most motion detectors have well-defined sensitivities and coverage area patterns that should be reviewed and matched carefully with the space and intended use. As with many other lighting technologies, these devices have been developed primarily for the commercial sector, but their energy-saving potential for homes is significant. Research conducted for The Lighting Pattern Book for Homes suggests that motion detectors can save up to 40% of lighting energy for bathrooms, 30% for bedrooms and kitchens, and 20% for living rooms and kitchen dining areas.
A photosensor is a light-detecting device that turns a lamp on when the surrounding light level drops below a specified minimum. Typically, photosensors operate exterior luminaires that are on all night and off during the daytime. They can also be used to operate luminaires in daylit areas where security is a concern, such as lobbies and entries.
Central controls allow a resident or facility manager to control switches, sensors, and dimmers located throughout a building. They can be used to monitor the lighting in a house, turn off luminaires that have been left on unnecessarily, and turn on lamps as needed for security. Security systems, receptacles, telephone jacks, and cable television jacks can also interface with some types of central controls. Central controls can be expensive and complex to install, and so are best used in large homes or multi-family buildings, especially for exterior areas and common areas like hallways, stairs, and entrances.
The Lighting Pattern Book for Homes was sponsored by Bonneville Power Administration, California Institute for Energy Efficiency, Empire State Electric Energy Research Corporation, New York State Energy Research and Development Authority, Niagara Mohawk Power Corporation, and North Carolina Alternative Energy Corporation.
TABLE 1. COMPARISON OF THE EFFICACIES OF SOME COMMON HOUSEHOLD LAMPS
Rated Lamp Light Output Lumens Type of lamp Watts in Lumens Per Watt Incandescent R-40 flood 150 1,900 13 PAR 38 flood 150 1,740 12 PAR 38 halogen flood 90 1,270 14 IR PAR 38 halogen flood 60 1,150 19 Low voltage MR 16 BAB 20 280 14 A-19 100 1,750 17 A-19 60 880 15 A-19 halogen 100 1,880 19 A-19 halogen 60 960 16 Tubular halogen 500 11,000 22 Tubular halogen 300 6,000 20
Fluorescent 8 circline RE730 (Magnetic ballast) 27 1,150 43 Compact (Electronic, self-ballasted) 26 1,550 60 48 T12 RE730 (Magnetic ballast) 46 2,800 61 48 T8 RE730 (Electronic ballast) 37 2,850 77
Electrode-less (Induction) Reflector 23 850 36 A 85 6,000 70
Sources: The Lighting Pattern Book for Homes, and manufacturers' data sheets.
Decoding Lamp Descriptors A the standard light bulb shape R reflector ER ellipsoidal reflector PAR parabolic aluminized reflector IR infrared reflecting MR multifaceted reflector T12 tubular shaped fluorescent lamp that is twelve-eighths of an inch in diameter T8 tubular shaped fluorescent lamp that is eight-eighths, or one inch in diameter RE730 rare earth phosphor, color rendering index of 70-79, 3,000 K color temperature RE830 rare earth phosphor, color rendering index of 80-89, 3,000 K color temperature
WHAT DIFFERENCE DOES IT MAKE?
Most people understand that home appliances consume a lot of electricity, but they may not realize that lighting is like an appliance, too. It accounts for 6% to 20% of the electricity consumed in homes in the United States. In conducting economic analyses for The Lighting Pattern Book for Homes, we found significant benefits when we compared the annual operating costs of our energy-efficient lighting designs to 36 typical designs for various rooms of a low-to middle-income residence. The annual operating cost formula that we used accounts for the number of lamps, lamp wattage, a power reduction factor for dimmers or motion detectors, cost of electricity, and prorated lamp replacement cost.
For 34 typical designs where we simply replaced the lamps with more efficacious lamps, we found an average of 26% annual operating cost savings. In 16 common designs where we replaced typical manual on/off controls with dimmers, timers, or sensors we found an average of 45% savings. The greatest average savings, 57%, occurred in 20 typical designs where we replaced luminaires with ones that are dedicated to efficacious lamps and in 23 designs where we planned for remodeling or new construction, using an integrated system of efficacious lamps, efficient luminaires and appropriate controls. In all cases, we maintained or improved the quality of lighting in the rooms, and reduced energy consumption.
Designing lighting for efficiency means more than just replacing a light bulb. It also involves determining the right light level for the space, choosing the most efficient luminaire for the job, using task lighting, and installing the right controls and making them accessible. The finished product of a well thought-out lighting design is better quality lighting that uses less energy.
Figure 1. Typical Design. One vanity light containing three 60-watt globe incandescent lamps controlled by a wall-mounted switch provides ambient lighting and lighting for the mirror. Used two hours per day, this design would cost $17 to operate annually. If the wall-mounted switch were replaced by a motion detector, the annual operating cost would drop to $10.
If the typical vanity light were replaced with one that contained two 18-watt, 10.5 inch fluorescent twin-tube lamps and one electronic ballast controlled by a wall-mounted switch, then the annual operating cost would be even lower, $6.50.
Figure 2. Design for remodel or new construction. If the same bath were remodeled, or built anew, the annual operating cost would be significantly decreased, to $3, by installing a soffit containing one 32-watt, four-foot T8 RE730 linear fluorescent lamp and one electronic ballast. This design modifies the light distribution in the room, directing more light to the critical task areas!
Illustrations from The Lighting Pattern Book for Homes, (c)1993, Rensselaer Polytechnic Institute.
Figure 3. Typical lighting design. Four recessed down lights, each containing one 75-watt R30 lamp, provide ambient lighting. Two table lamps, each containing two 60-watt A-lamps, provide lighting for reading. A recessed accent luminaire containing a 75-watt R30 lamp highlights the fireplace and is controlled by a separate wall-mounted switch. The annual operating cost (including electricity and lamp replacement costs) for lighting this room with this design is $83, based on a rate of ten cents per kilowatt-hour, and three hours of use per day.
Figure 4. Design for remodel or new construction. For a different light distribution pattern in the living room, two valances and one soffit, containing a total of seven electronically ballasted 40-watt, 5-foot T8 linear fluorescent RE830 lamps, provide ambient lighting. Depending upon the dimensions of the room, 4-foot lamps also could be used. The table lamp contains two 13-watt compact fluorescent twin-tube lamps and one magnetic ballast. The valances and soffit each are controlled by a wall-mounted switch. The annual operating cost for lighting with this energy-efficient design is $37.
DAYLIGHT AS A LIGHTING TECHNIQUE
Like electric lighting, daylighting has sources, luminaires, and controls. Daylight sources are the direct sun, the sky which can diffuse the sun's light, and surfaces surrounding a building that can reflect sun or sky light into the building. Daylight luminaires are the windows and skylights that admit daylight into the building. Examples of daylight controls are tinted glass and films, blinds, curtains, overhangs, and shades that reduce the brightness and change the distribution of daylight, and sensors and switches that control electric lighting in the daylit space.
Most daylit rooms average 10 to 12 hours per day of potentially avoided electric lighting; the proper use of electric lighting controls maximizes the energy savings available when daylight is used in a lighting design. For a simple yearly estimate of daylighting energy savings potential in kilowatt-hours, multiply the number of hours that lamps in a room would be on during the day, times 365 days times the watts consumed by the lamps, and divide by 1,000.
Some tips can help in using daylighting to your best advantage:
NEW LAMP OPTIONS AND LABELS
The Energy Policy Act of 1992 (EPAct) spurs manufacturers to improve and introduce new and more efficacious lamps. By October 31, 1995, EPAct will prohibit the manufacture of some low-efficacy lamps, including many standard incandescent reflector lamps and parabolic aluminized reflector lamps, and also ban some poor-color-quality and slightly lower-efficacy fluorescent lamps, such as the 48-inch cool white 40-watt T12 lamps. Table 2 shows the EPAct requirements. The incandescent reflector lamps that do not meet the minimum efficacy standards will no longer be manufactured.
A Federal Trade Commission ruling on lamp labeling issued in May 1994 applies to general service fluorescent lamps, medium base (integrally ballasted) compact fluorescent lamps, and general service incandescent lamps (both reflector and non-reflector). Special types of lamps are excluded from the ruling.
The new labels described in this ruling must appear on lamp products that are manufactured after May 13, 1995. As shown in the illustrations below, the label will include the light output of each lamp, expressed in average initial lumens; the electrical power consumed (energy used) by each lamp included in the package, expressed in initial wattage; and the life of each lamp expressed in hours. If more than one lamp is included in the package, the number must be stated, and the design voltage of each lamp stated, if it is other than 120 volts.
Promotional materials displayed or distributed at the point of sale must include the statement, Before purchasing this appliance, read important energy cost and efficiency information available from your retailer. If retailers make claims about the cost of operation of lamps, they must disclose the assumptions upon which the claims are based, such as purchase price, unit cost of electricity, hours of use, and patterns of use. Catalogs intended for use by consumers must also carry the information required for the labels and for any operating-cost claims for the products being sold.
In the near-term, some consumers and specifiers may be frustrated, confused and inconvenienced because products they are accustomed to using will no longer be available. Also, suitable replacement products may cost more and may not have the same light distribution patterns as the old products. The lighting community and the electric utility industry should prepare for this changeover in 1995 by providing information to specifiers, retailers, and consumers about suitable lamp replacements.
Source: Federal Trade Commission 16 CFR Part 305, Issued May 13, 1994, Rules concerning disclosures of information about energy consumption and water use for certain home appliances and other products required under the Energy Policy and Conservation Act.
TABLE 2. EPACT EFFICACY REQUIREMENTS AND EFFICACIES OF INCANDESCENT R AND PAR LAMPS Nominal EPACT Minimum Typical Efficacy for Typical Efficacy for Lamp Required Lamp Standard Standard Wattage Efficacy Incandescent R Incandescent PAR (W) (LPW)(1,2,3) Lamp (LPW) Lamp (LPW) ________________________________________________________________________________________________ 40-50 10.5 11 (50-watt R30)(4) 6 (50-watt PAR36) 51-66 11.0 12 (65-watt R30)(4) 10 (55-watt PAR38) 67-85 12.5 11 (75-watt R40) 10 (75-watt PAR38) 86-115 14.0 12 (100-watt R40) 13 (100-watt PAR38) 116-155 14.5 13 (150-watt R40) 12 (150-watt PAR38) 156-205 15.0 10 (200-watt R40) 14 (200-watt PAR56) ________________________________________________________________________________________________
Notes: (1) Includes medium base lamps, 115-130 volt, diameter larger than 23/4. R20, PAR16 and PAR20 lamps are exempt from the standard. (2) ER, BR, colored, rough/vibration service, and specialty R and PAR lamps meeting the DOE definitions for such lamps, are exempt from the standard. (3) The standards apply to lamps manufactured or imported for sale in the United States after October 31, 1995. Lamps manufactured or imported before the effective date may be sold after the effective date regardless of whether they meets the efficacy standards. (4) Meets EPAct efficacy requirements. Source: The Impact of EPAct on Reflector Lamp Replacements by Dorene Maniccia, Jose Raffucci and Qianxiang Wang, presented at Institute for Electrical and Electronics Engineers Conference, Denver, CO, October 5, 1994
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