Bright Ideas Office Lighting 101

Transcription

1 HUMANSCALE PRESENTS Bright Ideas Office Lighting 101 With recent improvements in lighting technology and a better understanding of lighting issues, you can have the best of both worlds reduced lighting costs and increased worker comfort and performance. CONTINUING EDUCATION Use the learning objectives below to focus your study as you read Bright Ideas Office Lighting 101. To earn one AIA/CES Learning Unit, including one hour of health safety welfare credit, answer the questions on page 192f, then follow the reporting instructions on page 230 or go to the Continuing Education section on archrecord.construction.com and follow the reporting instructions. LEARNING OBJECTIVES After reading this article, you should be able to: More effectively evaluate office lighting design Understand the importance of incorporating task lighting into an overall lighting plan Identify the environmental and worker health-related benefits of certain types of task lighting In the last 40 years, much advancement has been made in the area of lighting technology. Workspaces of the 1960s and 70s were designed around the belief that more light leads to better visual performance. Thus, they typically provided more light than the job required with little or no flexibility for the user. The result was wasted energy and a variety of human-factors issues, such as eyestrain and headaches. New scientific research and enhanced technologies have provided designers with smarter solutions. Unfortunately, many offices continue to use dated technology to illuminate workspaces. Today s workplace calls for flexible lighting systems that support the tools of the modern office, such as monitors and notebook computers. This suggests the integration of more appropriate lighting solutions into existing lighting plans, and the selection of the most advanced products for new-build situations. The more we come to understand about lighting the more we appreciate its importance. Lighting projects present a significant opportunity for us to add value to our facilities and improve the workplace, says James Woods, Energy Conservation Officer for the U.S. Department of Commerce. Office lighting design continues to move toward greater energy efficiency, while providing improvements for worker comfort and safety. This move toward environmentally responsible design can be further developed with the incorporation of task lighting into workplace lighting schemes that would typically use just ambient or overhead light sources. Recent research into the use of task lighting has provided evidence that incorporating positionable light sources into individual workspaces provides many benefits with regard to energy consumption. Additionally, it provides individual workers the freedom to position their light sources most comfortably. At the Department of State we ve learned from experience that our employees feel strongly about having good lighting, and that user-controlled lighting can help our people accomplish their missions. Energy and cost savings along with improved environments give us the best of both worlds,

2 says Richard Tim Arthurs, Energy Policy and Conservation Officer, Office of Facilities Management Services, U.S. State Department. In the 1970s, when it came to lighting our workspace, more was better. Recent research has shown us that more is not better, and in fact not desired by most workers. Providing too much light can lead to the following: Energy waste Emotional and physical discomfort for the office worker due to improper illumination of the work surface and glare on reflective surfaces (such as the computer monitor) Using positionable task lighting in addition to low ambient light can lead to the following: Improved lighting quality, comfort and control for workers Increased energy efficiency Task lighting can provide illumination where it is most needed on paper-based documents more economically than the most energy-efficient ceiling ambient light because task lighting is located closer to what s being lit. In addition, individual workers can gain control over their lighting as appropriate for the task being completed. The monitor document conflict The demands of differing tasks within the workplace create an obvious conflict in lighting requirements, says researcher Alan Hedge, PhD, CPE, Director of the Human Factors and Ergonomics Laboratory at the Cornell University Department of Design and Environmental Analysis. The majority of work that most office workers perform today is a combination of viewing a monitor and reading documents or other printed material. Yet these two tasks require significantly different levels of light. If the ambient lighting level is set at the appropriate level for reading printed documents (20 50 footcandles), the lighting intensity will be much too high for proper monitor viewing (5 10 footcandles required). This leads to glare on the surface of the monitor, substantial energy waste and a variety of worker productivity issues. However, if the ambient lighting level is brought down to a point which is appropriate for monitor viewing and movement throughout the workspace, then there won t be nearly enough light to read documents and other paper-based reading material. Light Bulb Comparison Chart LUMENS PRODUCED LIGHT QUALITY CRI (COLOR RENDERING INDEX) ENERGY CONSUMPTION BULB TEMPERATURE BULB LIFE COST OF BULB BULB LIFE (ON AVERAGE) BULBS NECESSARY (OVER 4.5 YEARS) ANNUAL ENERGY COST TOTAL COST (OVER 4.5 YEARS) Incandescent Bulb 100W 1690 White/Yellowish > W 500 F 1000 hrs $ Days 10 $21.90 $ Halogen Bulb 100W 1900 Very bright, white light > W (or more due to heat) 1800 F 2500 hrs $ Days 4 $21.90 $ Compact Fluorescent 26W 1825 Available from warm to crisp/cool >84 26 W 125 F hrs $ Days (4.5 Years) 1 $5.91 $40.6o * Assuming 6 hours of usage per day at $0.10 per kilowatt-hour Source: U.S. Department of Energy As we age, our eyes undergo several physiological changes including the development of opacities in our lens and a reduction in pupil size that result in our need for more light. The solution to this conflict is to lower the overall ambient lighting levels and provide individuals with positionable task lights to properly illuminate the reading material on the desktop. In this way, both the monitor and documents can be lit to appropriate levels for the tasks being performed. Bulb options and energy efficiency Today s task lights utilize one of three primary bulb types: incandescent, halogen or compact fluorescent. Compact fluorescents burn cooler and have proven to be more efficient than any other available task light source. A regular incandescent or halogen bulb works by heating a metal wire to a temperature at which it glows. This requires high temperatures, relatively large amounts of energy, and creates a hot bulb surface. In fact, halogen bulbs can reach temperatures of 1800º and have therefore been banned from many university dormitories because of their risk as a fire hazard. A compact fluorescent bulb is a low-pressure mercury, electric-discharge lamp in which phosphor coating transforms ultraviolet energy, created by electric discharge, into visible light. The fluorescent bulb remains much cooler and uses less energy than the other two, while providing the same amount of light. The first practical electric lamp, developed by Thomas Edison in 1879, converted less than one percent of electricity into light. Today s household incandescent bulbs convert 6 7 percent of their electrical input into light. The rest is wasted as heat. Classic 4-ft fluorescent systems convert approximately 19% of their energy into light. Today s compact fluorescent lamps, five inches in length, or less, can be 50 times more efficient than Edison s original lamp and eight times more efficient than an incandescent light source capable of the same light output. For example, a 13-watt compact fluorescent task light will produce the same light output as a 75-watt incandescent light, burn cooler and consume only one-quarter of the electricity. As we age, we need more light to read The older we get, the more light we need to see. Research indicates that the visual performance of those in their 20s is about eight times better than those in their 60s, almost four times better than those in their 50s. Those 61 and older require more than 350 percent more contrast than do those in their 20s. Relative Contrast Required as a Function of Age Relative Contrast Required Age

3 Despite being considered task lights, under-the-bin lighting solutions are a major source of glare and are not an adequate alternative to positional task lighting. This increased need for light is due to a number of physiological changes in our visual system that occur as we age. The term presbyopia means old eye and is a vision condition involving the loss of the eye s ability to focus on close objects. Presbyopia, also referred to as farsightedness, occurs gradually over a number of years. Symptoms are usually noticeable by age 45 and continue to develop until the process stabilizes some years later. In the eye, the crystalline lens is located just behind the iris and the pupil. Tiny ciliary muscles push and pull the lens, adjusting its curvature, and thereby adjusting the eye s focal power to bring objects into focus. As individuals age, the lens develops opacities and becomes less flexible and elastic, making accommodation more difficult. Because these changes result in inadequate adjustment of the lens of the eye for various distances, objects that are close will appear blurry. The muscles which control the diameter of the pupil also deteriorate with age. This reduces the size of the pupil, and limits the range and speed with which the pupil can adjust to varying light levels. This, combined with the increased opacity of the crystalline lens, increases the amount of light necessary to achieve the same level of retinal illumination. Eyestrain and accompanying headaches, which can result from working under inadequate illumination, are aggravated by aging. Eye fatigue may result in blurry vision and dim lighting aggravates the problem. Task lighting allows us to achieve the correct levels of illumination, regardless of the task or vision requirements, by changing the distance between the light source and the lit object closer for more light, further away for less. It also allows us to correctly position the angle of light to eliminate glare and veiling reflections. Task lighting saves eyes and energy Task lights, because they are closer to the work surface, are a considerably more effective means of lighting a desktop than are overhead fixtures. A task light using a 26-watt compact fluorescent lamp will consume far less energy to illuminate a work area than will a typical overhead lighting fixture. A work environment can maintain lower levels of overhead lighting by illuminating desktops with energy-efficient task lights. In addition, maintenance and bulb replacement costs are less with task lighting. Research suggests that with the use of energy efficient lighting technologies, we can reduce overall electrical use for lighting by half, a move that would save over $20 billion annually and decrease powerplant emissions by millions of tons. According to the California Energy Commission, lighting accounts for 23 percent of the electricity used in the state. The actual figure may be considerably higher, say other sources. Five percent of electricity used for air conditioning, for example, goes to eliminate heat generated by lighting. In general, however, the EPA estimates that lighting accounts for percent of the electricity used annually in the United States. Since the 1970s, huge strides have been made in office lighting efficiency. Still, say California officials, the potential exists to reduce lighting energy use and peak demand by an additional 50 percent by 2020 while still improving the quality of lighting to the end user. Research by the U.S. Environmental Protection Agency has found that lighting for industry, offices, stores and warehouses represents from percent of the total lighting electricity use in the United States. The Institute for Research in Construction, an arm of the National Research Council Canada, has found that if energy-efficient lighting were used everywhere it was profitable, the electricity required for lighting would be cut by 50 percent, and aggregate national electricity demand would be reduced by 10 percent. This reduction in demand would significantly reduce power plant emissions, pollutants, and wastes, say federal researchers. Flux, illuminance and luminance Total flux, in lumens, is the parameter that bulb manufacturers use when describing the total amount of light given off by a bulb in all directions. Lumens do not, however, tell us how much light will be received where it is needed. Illuminance, on the other hand, tells us how much light will reach a given surface. Illuminance is generally measured in lux: a short form for lumens per square meter of surface area, the metric equivalent of footcandles (which represent lumens per square foot). There are lux in one footcandle, but the lighting industry typically rounds this factor off to 10.0 for the sake of simplicity. Lowered ambient lighting levels for proper monitor viewing combined with task lights for proper document illumination provide the right amount of light for different tasks while saving money and improving worker comfort, productivity and job satisfaction.

4 Dated lighting schemes based solely on overhead fixtures provide an incomplete and inefficient lighting solution that wastes energy and has both physical and performance implications for workers. IES Illumination Categories & Recommended Values ACTIVITY CATEGORY LUX FOOTCANDLES Indicates typical office task Public spaces with A dark surroundings Simple orientation for short B temporary visits View CRT screen Working spaces where visual tasks C are only occasionally performed Performance of visual tasks of D high contrast or large size Read standard document, photocopy or newspaper Performance of visual tasks of E medium contrast or small size View photo in moderate detail; reference phone book Performance of visual tasks of F low contrast or very small size Performance of visual tasks of G low contrast or very small size over a prolonged period Performance of very prolonged H and exacting visual tasks Performance of very special I visual tasks of extremely low contrast A-C for illuminances over a large area (i.e. lobby space) D-F for localized tasks G-I for extremely difficult visual tasks Thirty years ago, standards of the Illuminating Engineers Society of North America (IES) called for general office lighting in the range of footcandles (1,000 1,500 lux). Huge, increasingly cubicled floorplates, often without any natural, outside illumination, were lighted, for the most part, by banks of 4-ft, ceiling-mounted fluorescent troffers (recessed fluorescent fixtures) that, in too many cases, resembled stadium floodlights in their intensity. By 2002, nearly all office tasks were being performed on desktop computers and average ambient light levels in the American workplace declined to one-third of 1970s levels. Today, ambient office lighting is likely to be in the range of footcandles ( lux), which is still far more light than is necessary for getting around the office or viewing a computer screen. According to IES, computers are best viewed in an environment where the ambient lighting is 5 10 footcandles ( lux), whereas most reading requires footcandles ( lux). Luminance, in candela per square meter (cd/m2 is a measure of how bright an object appears (1 cd/m2=0.29 foot-lamberts, the imperial unit for luminance). Luminance is a representation of the amount of light seen by the eye. Luminance is sometimes specified for critical lighting designs (e.g., IES Recommended Practice RP-24 for Offices with Video Display Terminals). However, illuminance is usually the parameter of preference because it is indirectly related to what the eye sees. Knowing the reflectance properties of illuminated surfaces, it is possible to calculate luminance from illuminance using procedures in the IES Lighting Handbook. IES lighting recommendations are usually given in terms of illuminance because it is more practical to measure. If we compare a lighting fixture to a shower head, then the lumen output, or total flux, is the rate of flow of water and illuminance is the amount of water collected in a bucket at a given time. The key point is that the same total flux can give different amounts of water in the bucket, simply by moving the bucket, or by changing the spray pattern or by changing any physical obstructions between the source and the bucket. Total flux doesn t specify how much illuminance will be provided where it s needed. This is true, in part, because the luminaire, reflectors, lenses and other optical media can greatly affect the flow of light from the source to the work surface. Failure to remember this is a frequent cause of poor lighting design, especially in retrofit applications. For lighting designs, we should not assume that two lamps with the same lumen rating will each give the same amount of light where needed.

5 Rough estimations of illuminance can be made by dividing the candelas by the square of the distance between the light source and the surface illuminated. For example, if a fixture gives 2000 candelas in the downwards direction, and if we mount that fixture in a 10-ft high ceiling, then the illuminance from that fixture will be approximately 2000/102=20 footcandles at the floor directly below the fixture. In metric units, one would calculate 2000/(3.048m)2=215 lux. Calculations of this type work as long as the distance to the surface is at least four times greater than the maximum dimensions (i.e., length or width) of the light source. For shorter distances, the calculations may still be used but they are subject to a greater uncertainty. Ballast technology All fluorescent lamps require ballasts, which stabilize and control the electrical current that gets sent to the lamp. These ballasts are available in two primary types: magnetic and electronic. Magnetic ballasts use long-standing technology, and with few components susceptible to failure, they are likely to last for 20 years or more, far longer than most electronic ballasts. However, electronic ballasts have the edge in performance and health considerations. Electronic ballasts are more energy efficient than magnetic ballasts because they operate lamps at higher frequencies (above 20,000 Hz versus 60 Hz for magnetic ballasts). High-frequency operation also reduces perceptible flicker. The health benefits seen with electronic ballasts are attributable to the reduction in flicker as visual demands are reduced. Electronic ballasts can increase the efficiency of fluorescent lighting systems by as much as 29 percent over systems using magnetic ballasts, while at the same time extending bulb life. Electronic ballasts are either instant start or rapid start. Instant start ballasts, which produce a high starting voltage which is then quickly reduced, are more energy efficient. Rapid start ballasts heat the lamp cathodes before triggering illumination, helping to maximize the life of the ballast and the bulb. Among the findings of National Research Council Canada researchers Guy Newsham and Jennifer Veitch, designs utilizing electronic ballasts: resulted in workers typing 21 percent faster during creative writing exercises improved workers reaction times by eight percent lowered incidence of headaches and eyestrain Our findings provide good news for the lighting community, they conclude. The goals of improving energy efficiency and lighting quality are compatible. People who worked under electronic ballasts showed better visual performance, did better on reading and writing tasks and rated the tasks less difficult. For Detroit-based Smith Group, Inc., an A/E firm with its own in-house lighting group, the goal of a soon-to-be-completed, nine-building campus in Van Buren Township, Michigan, for auto parts supplier, Visteon, was the absolute minimization of energy costs, says James Luckey, AIA, Senior Design Architect. The first consideration was natural light. To allow as much light as possible into interiors, Luckey designed all of the 100, ,000-sq-ft buildings to be extremely narrow, 64 feet in width. We wanted this project to conform to the European standard, in which workers are never more than 10 meters from a window, he says. Exposures are large: sills of 15-ft-wide windows are only 2-ft off floors; headers are 10-ft above floor height; ceilings at 11ft 6 in. We like, whenever possible, to push ceiling height, says Luckey. Ambient lighting, via direct-indirect pendants (75 percent upward, 25 percent downward), centered in 20-ft ceiling bays, 30 inches beneath ceilings, is at 30 footcandles and is automated. Most days, in all likelihood, Lucky figures, ambient lighting will not be turned on. For sparkle, Smith used café and track lights. Each 50-sq-ft workstation will also have at least one compact fluorescent task light capable of providing footcandles where it is needed. The use of task lighting allows higher intensities only where that level of light is needed, says Luckey. In a computer environment, the goal is to minimize light pollution. This project, he says, is in keeping with what we try to do with every project. If ceilings are shallower, we have no choice but to put lights in the ceiling plane, but we prefer not to. At Visteon s new corporate campus, which will open incrementally from August through December, workers not only will control lighting within individual workstations, but individual controls will allow them to control floor-distributed heating and cooling as well. Overall lighting consumption, Luckey says, is one watt per sq ft; lighting and miscellaneous power consumption, 2.25 watts per sq ft the SMITH GROUP: TASK LIGHTING ESSENTIAL figure excludes air-handling. Perhaps more importantly, Luckey says, ASHRAE 90.1 sets a standard of 94,842 BTUs (British thermal units) per square foot per year. Visteon Village will consume about 59,000 BTUs per square foot per year a 37 percent energy reduction from the code allowance. That number includes under-floor heating and cooling consumption. When it comes to lighting, there is a lot more to think about than most people realize, says Denise B. Fong, IALD, LC, LEED, a principal at Seattle-based Candela Architectural Lighting Consultants. It is not enough to rely upon standards, Fong says. One of the things we do because the energy code tells us to do it, is to calculate consumption by watts per square foot, but that tells us little about the quality of light. We don t see, for instance, what the light meter measures, says Fong. We see reflected light. If you were to meter light in a room painted half black and half white, a light meter will give you the same reading in either space, but to our eyes, the area with black surfaces will appear darker because there is less reflection. She suggests a growing interest in the use of task lighting, mentioning, Task lighting is not something we lighting designers pay much attention to, but there are cost benefits associated with task lighting. In general, the use of task lighting enables you to reduce the general ambient light level. There are still a lot of projects out there where all the lighting is in the ceiling, but energy codes are forcing us to rethink that strategy, Fong says. According to an assessment by the Lighting Research Center at RPI, more than one-third of all U.S. workers occupy partitioned workstations, and under-shelf task lighting accounts for 90 percent of all task lighting sold. If partitions are shelved, and if the task light is beneath the shelf, Fong says, light is not where you need it, and glare is almost always a problem. Glare happens when the light source, the object being lit and the eyes are all in the same plane. In the case of under-shelf lighting, the light originates under the shelf, hits the work surface and bounces directly into the eyes of the worker. The solution, Fong says, is an asymmetric task light that uses specially designed reflectors to concentrate light in one direction. This allows the user to position the light off to the side so that the beams of light are directed across the front of the user, instead of toward them. If you are right-handed, an asymmetric task light located to the left of your work area will put the highest light output in the middle of your work surface, and the light will bounce away from you so you don t get any glare from the lamp, she adds. The most common design error, clearly, is the mismatch between where light is being delivered and where people are utilizing that light, says Alan Hedge. All too often we put light into a building without knowing the ultimate layout. Even if the layout is known, things can happen that are not foreseen. Offices may be partitioned differently by new tenants, for instance, and the new layout can result in a feast or famine situation, so far as light is concerned. Some workers may complain of glare and headaches; some may be in the dark. In a study conducted in 1990, Cornell researchers drew on an American Society of Interior Designers survey in which 68 percent of employees complained about the light in their offices and 79 percent of VDT users wanted better lighting. The Cornell study came to the conclusion that eyestrain was the number one health hazard in the workplace ahead of radiation, asbestos, or exposure to AIDS. Hedge says eyestrain remains the number one complaint in the office environment, and the degree of dissatisfaction is difficult to ignore. It confirms the need to identify the best available methods of lighting. How essential a component is task lighting in creating an effective office lighting scheme? It is likely to be the most effective solution in any environment in which workers are doing both paper work and computer work, says Hedge.

6 The color of light One aspect of lighting that often gets overlooked is bulb color temperature, which describes the color appearance of the bulb, not the object being viewed. Color temperature ranges from 3000 Kelvin for warm sources like incandescent lamps, to approximately 6500 Kelvin for cool sources like daylight fluorescent. Color temperature data is readily available from lamp manufacturers. The selection of color temperature should be considered relative to the application. Lamps that are high to very high in color temperature (5,000K to 7,500K) provide improved visual acuity compared to lower-color temperature lamps (typically 3,500K) at the same light level. Visual acuity is generally defined as sharpness of vision, with normal visual acuity rated at 20/20. High color temperature lamps are rich in the blue portion of the color spectrum and have a noticeably cool appearance. The Color Rendering Index, or CRI, of a bulb specifies on a scale of 1 to 100 how colored objects appear under that bulb s light compared to their appearance in daylight. A CRI of 100 means no difference, while a low CRI could mean a big difference. Incandescent lamps typically have CRIs above 90, but that doesn t mean that they always give suitable results. Suppose, for example, we wish to illuminate white cabinets in a kitchen or a hospital examination room. A design objective might be to enhance the impression of whiteness, cleanliness and sterility. In this case, the color temperature of incandescents would be too low to achieve the desired effect. As a general rule, one should therefore select color temperature first, then pick the lamp giving the optimum CRI for the application. Most fluorescent lamps operate at 3,000K to 4,100K, with a CRI from the low 50s to 86, but recent technology gains now give us fluorescents with CRIs above 90. A full-spectrum lamp is generally defined as a lamp having a Color- Rendering Index (CRI) of 90 or above and a color temperature of 5,000 degrees Kelvin or above. CLICK FOR ADDITIONAL REQUIRED READING The article continues online at: archrecord.construction.com/resources/conteduc/archives/0409human-1.asp. To receive AIA/CES credit, you are required to read this additional text. For a faxed copy of the material, contact Humanscale Customer Service at (800) or via at info@humanscale.com. The following quiz questions include information from this material. LEARNING OBJECTIVES More effectively evaluate office lighting design Understand the importance of incorporating task lighting into an overall lighting plan Identify the environmental and worker health-related benefits of certain types of task lighting INSTRUCTIONS Refer to the learning objectives above. Complete the questions below. Go to the self-report form on page 230. Follow the reporting instructions, answer the test questions and submit the form. Or use the Continuing Education self-report form on Record s website archrecord.construction.com to receive one AIA/CES Learning Unit including one hour of health safety welfare credit. QUESTIONS AIA/ARCHITECTURAL RECORD 1. Ambient light levels in the American workplace have declined to onethird of 1970s levels. Today, ambient office lighting is likely to be in the range of: a footcandles. b footcandles c lux d footcandles 2. Those 50 years of age and older require what percentage more contrast than do those in their 20s? a. 125 percent b. 50 percent c. 350 percent d. 250 percent 3. A 13-watt compact fluorescent task light will produce the same light output as a 75-watt incandescent light. a. true b. false 4. Lamps that are high to very high in color temperature (5,000k to 7,500k) provide improved visual acuity compared to lower-color temperature lamps (typically 3,500k) at the same light level. a. true b. false 5. According to the California Energy Commission, lighting accounts for what percentage of the electricity used in the state? a. 7 percent b. 13 percent c. 23 percent d. 35 percent 6. Today s household incandescent bulbs convert what percentage of their electrical input into light? a. 6 7 percent b. 3 percent c. 19 percent d. 28 percent 7. California officials say the potential exists to reduce lighting energy use and peak demand in the state by up to what percentage by the year 2020? a. 15 percent b. 35 percent c. 50 percent d. 375 percent 8. If a fixture gives 2000 candelas in the downwards direction, and if we mount that fixture in a 10-ft high ceiling, the illuminance from that fixture will be how many footcandles at the floor directly below the fixture? a. 20 b. 50 c. 100 d High-frequency electronic ballasts can increase the efficiency of fluorescent lighting systems by what percentage over systems using magnetic ballasts? a. 9 percent b. 14 percent c. 29 percent d. 83 percent 10. Which has the greater light output: a 26-watt fluorescent lamp or a 100- watt incandescent lamp? a. a 26-watt fluorescent b. a 100-watt incandescent

7 What is task lighting and why should we use it? Task lighting provides the correct amount of light for the task being performed. Viewing a computer monitor or walking down the aisle requires far less light than does reading a typewritten page, making it neither effective nor efficient to light the entire environment at the same level. When utilizing task lighting, the general lighting level in the facility can be lowered to a level appropriate for monitor viewing, thus creating a softer, more pleasant atmosphere and saving energy. Work surfaces are supplemented with task lighting to give workers total control over where and how much light they need for other tasks, such as reading a document. Why choose a compact fluorescent task light? Compact fluorescent bulbs use less energy than incandescents (about one fourth), output more light (approximately three times as much) and last up to 10 times longer. Compact fluorescent bulbs are also much cooler in operation than regular incandescent bulbs or halogen bulbs and are, thereby, safer and more comfortable to work near. How does a mini-fluorescent bulb differ from earlier generation fluorescents? As I understand it, mini-fluorescents were used in earlier generation task lights but fell out of favor when halogen bulbs were introduced. First generation mini or compact fluorescent bulbs suffered from flicker, low light and an audible hum. These objectionable characteristics have been eliminated in the current generation of mini-fluorescents and accompanying ballasts. Today s fluorescents are long-lasting and have a light output as good as, if not better than, halogen or regular incandescent bulbs. FREQUENTLY ASKED QUESTIONS What Color Rendering Index (CRI) should task light bulbs have? CRI is a method for describing the effect of a light source on the color appearance of objects being illuminated. A CRI of 100 represents the reference condition of daylight (and thus the maximum CRI possible). In general, low CRI illumination may render some colors unnatural and lamps with a CRI under 60 should not be used. It has been proven that at a certain point, the higher the CRI, the lower the illuminance. A CRI in the 80s is good for all general tasks. I don t like the light given off by fluorescent bulbs. Can they be made to give off a warmer light like incandescents? Yes, compact fluorescent bulbs are available in color temperatures ranging from 2700K for warmer light to approximately 4100K for cooler sources like daylight fluorescent. I ve heard that full-spectrum lighting is better than regular fluorescent lighting. Is that true? The short answer is no. Any bulb with a CRI of over 90 is considered a fullspectrum bulb. Full-spectrum lighting is neither better nor worse than any other lamp type. Claims made for its beneficial effects go beyond what scientific literature will support. What is the difference between a magnetic and electronic ballast? Magnetic ballasts use coiled wire to create a magnetic field that transforms voltage. A magnetic ballast does not change the frequency of the power to the lamp it remains the same as the input power, which in the U.S. is 60 Hz. Electronic ballasts use solid-state components to transform voltage, while also changing the frequency from 60 Hz to 20,000 Hz or higher, depending on the ballast. Because electronic ballasts don t use coils or electromagnetic fields, they can function more efficiently and cooler than magnetic ballasts. However, they are also more prone to failure. GLOSSARY Color Rendering Index (CRI): method for describing the effect of a light source on the color appearance of objects being illuminated. A CRI of 100 represents the reference condition of daylight (and thus the maximum CRI possible). In general, low CRI illumination may render some colors unnatural. Footcandle: unit of measurement indicating how much illumination reaches a surface, equal to one lumen striking an area of one square foot. Ballast: a device used with an electric-discharge lamp to obtain the necessary circuit conditions (voltage, current and wave form) for starting and operating. A ballast can be electronic or magnetic. Lumen: the unit of measurement used to describe the output from a light. Lux: unit of illumination closely equivalent to 1/10 of one footcandle. Two-Component Lighting: combination of indirect general (ambient) light and task lighting. ABOUT HUMANSCALE Humanscale designs and manufactures ergonomic products for a more comfortable workplace. From the Freedom chair to the Diffrient Light each product is designed to improve the health, efficiency and quality of work life. Humanscale s seating, monitor arms, lighting, keyboard supports and other ergonomic accessories follow the belief that if a design solves a functional problem as simply and elegantly as possible, the resulting form will be honest and timeless. Headquartered in New York City, with global distribution, Humanscale remains the leader in ergonomic design. For more information contact Customer Service at ; or visit the website at (800)

8 CONTINUING EDUCATION Program title: Bright Ideas Office Lighting 101, sponsored by Humanscale, (09/04, page 192a) 094SPONM AIA/CES Credit: This article will earn you one AIA/CES LU hour of health safety welfare credit. (Valid for credit through September 2006) Directions: Select one answer for each question in the exam and completely circle appropriate letter. A minimum score of 70% is required to earn credit. 1. a b c d 6. a b c d 2. a b c d 7. a b c d 3. a b c d 8. a b c d 4. a b c d 9. a b c d 5. a b c d 10. a b c d Last Name First Name Middle Initial or Name Firm Name Address City State Zip Tel Fax AIA ID Number Completion date (M/D/Y): Check one: $10 Payment enclosed. (Make check payable to Architectural Record and mail to: Architectural Record/Continuing Education Certificate, PO Box 682, Hightstown, NJ ) For Customer Service, call: Charge my: Visa Mastercard American Express Card# Signature Exp. Date Check below: To register for AIA/CES credits: Answer the test questions and send the completed form with questions answered to above address or fax to For Certificate of Completion: As required by certain states, answer test questions, fill out form above, and mail to above address. or fax to Your test will be scored. Those who pass with a score of 70% or higher will receive a certificate of completion. Material resources used: Article: This article addresses issues concerning health and safety. I hereby certify that the above information is true and accurate to the best of my knowledge and that I have complied with the AIA Continuing Education Guidelines for the reported period. Signature Date Reprinted with permission from Architectural Record, September 2004