Everything You Ever Wanted to Know About Lighting...But Were Too Afraid to Ask

April 1, 2000
Shedding some light on the subject of lamps, luminaires, and lighting controls.

Flip a switch, move a table lamp a little to the left, adjust the Venetian blinds just so: Interacting with light in the home environment is commonplace. This intimate connection with lighting has been translating into commercial facilities as well. Light fixtures and lighting controls are becoming more responsive; the efficiency of lamp technology is increasing; and the benefits of high-quality lighting are adding up.

Curious about where to start?
Evaluate what occupants need, consider what types of tasks are performed, and what features in the space may cause discomfort (windows, computer screens, highly reflective surfaces, and glass-framed artwork). The mission is to design a system that enables workers to perform at maximum efficiency, employing the products and practices that lower costs and increase productivity. With careful planning, facilities managers and design professionals can create enhanced environments.

How exactly does lighting improve productivity?
Productivity is a lot like the weather; everyone talks about it but no one does anything. Of course, the biggest problem with discussing the lighting environment’s relationship to work performance is that productivity is so hard to quantify. “Productivity can be typing speed, rate of error, time spent at your desk. It can mean a whole series of things,” says Carol Jones, senior research scientist and lighting program manager, Battelle, Cambridge, MA. Because of the ambiguity surrounding the issue, according to Jones, many facilities professionals are skeptical of improving end-user performance with lighting.

Fortunately, lighting researchers have honed their methodology to mitigate extraneous influences. Light Right, a consortium of lighting designers, researchers, and manufacturers, is engaged in research to accurately measure the impact of lighting changes on end-users. Adds Jones, “We believe there is as an impact of lighting on people and their productivity.” The results of Light Right’s experiments are expected in 2001.

“The ways in which lighting has become much more adaptable at the individual workstation is of major interest to people. Controllability is key,” explains Judy Heerwagon, a lighting consultant based in Seattle. To create an enhanced lighting environment, Heerwagon recommends facilities managers use questionnaires after lighting upgrades to gauge end-users’ impressions. Also allowing workers to choose elements in their office space as much as feasible will lead to fewer complaints and an improved working environment.

Why is a lamp’s CRI or CCT important?
The Color Rendering Index (CRI) is the reason that the shirt and pants you thought matched so well at home seem to clash in the restroom at work. The closer the CRI of a lamp is to 100, the more “true” it renders colors in the environment. For individuals, such as graphic artists who perform tasks that require color precision or discrimination, lamps with a high CRI are recommended. Full-spectrum lamps are available that offer a CRI of over 90.

Warm and inviting are some of the words used to describe environments that contain lamps with a Correlated Color Temperature (CCT) of 3000K. Coffee shops, restaurants, and hotel lobbies are a few applications in which cozy lighting environments are desirable. Hospitals, cafeterias, classrooms, and conference rooms are areas where an image of neatness is important. Lamps that appear cool — measuring a CCT of 4100K — are most appropriate for these types of applications. By comparison, daylight measures 5000K, and neutral lamps have a CCT of 3500K.

What are the differentiating characteristics of incandescent, fluorescent, and high-intensity discharge?

Incandescent lamps:
• Appear “warm” in color and have excellent color rendering.
• Are the least efficient of general lamp types due to the amount of energy consumed heating the filament in order for the lamp to turn incandescent.
• Have a short lamp life of between 500 and 3,000 hours.
• Are easy to install because no ballast is required.

Fluorescent lamps:
• Are available in a complete range of color combinations.
• Produce low heat.
• Require a more extensive installation because ballasts are a necessary part of the fixture.
• Have an extremely long life of up to 24,000 hours.
• Due to smaller sizes and screw base features, fluorescents can replace incandescent lamps.

High-intensity discharge (HID) lamps:
• Are ideal for large stores, warehouses, auditoriums, outdoor parking areas, and applications where efficiency is a priority.
• Have a warm-up period, which results in slower start-up.
• Deliver a large amount of light over a wide area.
• Have a long life of between 5,000 and 24,000 hours.
• Require ballasts.

What does the nomenclature system for labeling and identifying fluorescent lamps mean?
The most common fluorescent lamps used in commercial buildings today are T8s. According to the Lighting Research Council (LRC), Troy, NY, the ‘T’ indicates the shape of the lamp — tubular, while the number following the T reveals the diameter of the lamp in eighths of an inch. Therefore, a T8 lamp is tubular and 1-inch in diameter, whereas a T12 is likewise tubular but twelve-eighths of an inch or 1.5 inches in diameter.

The National Electrical Manufacturers Association (NEMA), Rosslyn, VA, has developed a system for designating compact fluorescent lamp types as well. A lamp labeled CFT13W is a compact fluorescent (CF), twin parallel tube (T), with a wattage of 13. The nomenclature “equation” for compact fluorescent lamps is CF plus (+) shape (T equals [=] twin parallel tubes, Q equals four parallel tubes in a quad formation, S equals square shaped, M equals any other multiple tube shape) plus (+) wattage. What follows this designation is often a slash (/) and the abbreviated base designation.

Dump or Recycle?
Users of mercury-containing lamps, such as fluorescent or high-intensity discharge (HID), will eventually have to decide the fate of expired bulbs. Due to increasing concern about the dangers associated with human and environmental interaction with mercury, the federal government has strengthened, clarified, and modified regulations. Less than a year ago, mercury-laden lamps were added to the Universal Waste classification. As of Jan. 6, 2000, says Steve Kirschner, marketing manager, USA Lamp & Ballast Recycling Inc., Cincinnati, testing lamps according to the Toxicity Characteristic Leaching Procedure (TCLP) is no longer an option. Under the Universal Waste rule, mercury-containing lamps can either be treated as hazardous waste and disposed of at a hazardous waste landfill or recycled.

The expense involved in these two procedures varies greatly. “In order for us to pick up a shipment five miles from here as hazardous waste, it’ll cost close to $500 just in transportation,” and this does not include other ancillary costs, Kirschner says. Traveling the same distance to pick up the lamps with the intent to recycle them is significantly less expensive, with transportation costing a mere $18. This cost difference is indicative of the high price of treating, transporting, and reporting the bulbs as hazardous waste.

Through the recycling process, according to Kirschner, lamps are crushed, components are separated, and the mercury is extracted through a retort process. The mercury powder is heated until it transforms into a vapor which is pulled by vacuum through distillation coils and cooled. The liquid mercury is then filtered to purify. “They’ve made it so easy to recycle, it would be silly not to,” says Kirschner.

How do T12, T10, T8, and T5 fluorescent lamps differ?
These four lamps vary in diameter (ranging from 1.5 inches to 0.625 or five-eighths of an inch in diameter). Efficacy is another area which distinguishes one from another. T8 lamps offer a 5-percent increase in efficacy over 34-watt T12 lamps, and have become the most popular choice for new installations.

Choosing Light Sources for General Lighting, published in 1998 by the Illuminating Engineering Society of North America (IESNA), New York City, states that although they are available in lengths similar to the T12, T8s require a different ballast. For retrofit, the T10 is compatible with T12 ballasts. The T10 also uses a higher-efficiency phosphor and has a greater efficacy than the T12.

T5s are straight tube lamps with a high efficacy. Due to their unique sizes (available only in “metric” lengths) and special ballast requirements, the T5 is not a favorable choice for many retrofits. It is important that the proper fixtures are used during T5 installations in order to reduce glare.

How can a lighting upgrade improve a facility’s return on investment?
Subject to final rulemaking, the U.S. Department of Energy (DOE), Washington, D.C., efficiency advocates, and lighting manufacturers have reached an agreement that magnetic ballasts will no longer be manufactured after April 1, 2005. “Magnetic ballasts typically operate at 60 hertz, which is the common operating frequency for electrical systems. Electronic ballasts operate at 20 kilohertz, so they operate at a higher frequency. [This] enables them to be more efficient at operating the lamp, so they use less power,” says Dorene Maniccia, manager of LRC partners program, Lighting Research Center (LRC).

Low-wattage lamps are often the first consideration when it comes to cutting lighting costs. However, choosing energy-efficient ballasts can substantially contribute to energy savings. The evolution of ballast technology is also lessening the price gap between magnetic and electronic ballasts.

“The big drivers for facilities professionals are the need for flexibility and ease with maintenance,” says Janice Rewers, marketing communications manager, lighting products, Magnetek, Nashville. Facilitating maintenance and reducing the need to purchase a range of products also affects overall costs. Multi-functional, universal input voltage ballast products can deliver those effects while reducing facilities headaches.

The other side of the energy-savings equation is reducing energy consumption through lighting controls. Two types of occupancy sensors — ultrasonic and passive infrared — are available. Ultrasonic sensors generate sound waves that bounce off objects. Occupancy detection occurs when the device senses that movement in a certain area has interfered with these waves. Passive infrared sensors (PIR) sense the difference in heat from a person vs. general room radiation. PIR sensors are passive, while ultrasonic are considered active.

Choosing the proper sensor depends on a given area’s configuration and conditions. Choosing the proper sensor also affects the bottom line. PIR sensors are available as wall-switch, wall-mount, ceiling-mount, and outdoor commercial-grade units. Wall-switch PIR sensors, used to replace traditional wall switches, are best suited for private offices, copier rooms, and storage spaces. Wall-mount units, that are typically mounted high on a wall, are best suited for rooms with high ceilings, conference rooms, hallways, classrooms, and stairwells. Ceiling-mount sensors, best suited for open office spaces, lobbies, and cafeterias, provide coverage for areas needing an overhead view. Outdoor commercial units are available for perimeter and loading dock lighting applications.

According to the LRC, the effectiveness and energy-saving potential of occupancy sensors is greatly influenced by proper installation. Start with determining the amount of time lighting is left on when a space is unoccupied. Additionally, facilities managers need to monitor patterns of light usage to determine true savings. Used correctly, occupancy sensors can lengthen lamp life and reduce wattage and operating hours. When paired with a lighting upgrade, savings can be significant.

Preheat, rapid-start, or instant-start — what ballast is the best?
How long does it take a fluorescent lamp to turn on after the switch is flipped? For ballasts that employ the preheat system, it may take a few seconds. Rapid-start and instant-start provide immediate starting. Traditional thought has been that by providing a higher starting voltage across the lamp in an instant-start system, lamp life may be significantly reduced. However, research from the LRC, published in the Guide to Selecting Frequently Switched T8 Fluorescent Lamp-Ballast Systems (1998), found “no evidence to support the common belief that, when operating cycles are short, rapid-start electronic ballasts for T8 lamps provide longer lamp life than instant-start electronic ballasts.” In areas where occupancy sensors are employed, and lamps are switched on and off more frequently than every three hours, both the instant-start and rapid-start systems demonstrate comparable lamp life.

What is group relamping and how can it reduce maintenance costs?
“In almost all cases, the cost of replacing the bulb is more than the bulb,” says John Bachner, communications director, National Lighting Bureau (NLB), Silver Spring, MD. This principle is the basis of a practice called group relamping, something Bachner says may seem counter-intuitive to some. The idea is that all lamps are installed, cleaned, and replaced at the same time, regardless of whether they have expired. This practice is a money saver and cuts the average cost per lamp replacement; allows work crews to spend less time on spot replacement and more time on other duties; and enables new lamps to be purchased in bulk — many times at volume-discount rates.

Interruptions for spot replacement are eliminated, building occupants can be made aware of a pre-scheduled time when the process will take place, and lamps can be ordered in advance. “Group relamping significantly reduces expenses in the short term, and big time in the long term,” Bachner concludes.

What can be done to prevent glare?
That light spot on the computer screen, the brightness “hole” on a glossy sheet of paper, and the light bouncing off a glass-framed piece of art are all examples of glare. Eyestrain, physical fatigue, an inability to concentrate, headaches, and muscle aches in the neck and shoulders are the results of this lighting nemesis. According to the NLB, “a 1-percent productivity loss among a $1 million/year workforce will cost a company $10,000 annually.”

Strategies are available to eliminate and prevent glare. Rule number one, according to Dr. Peter Boyce, head of the human factors program, LRC, is “you don’t want a direct view of the lamp from any normal viewing position.” Boyce explains that a “bright thing out in the edge of the field of view, [is] very distracting because the visual system is designed to turn your attention toward it.” The NLB recommends relocating items on the wall, reframing graphics with non-glare glass, reorienting workstation or computer screens, and replacing the lens or louver grid on overhead lighting as less expensive alternatives to replacing the overhead lighting altogether.

Parabolic louvers for ceiling-recessed parabolic luminaires will help reduce glare to surfaces, says the LRC’s Maniccia. Because the parabolic luminaire directs light downward, caution should be observed to ensure that a cave-like effect does not result, because vertical surfaces may appear dark and gloomy.

Specular reflectors and diffusers are useful accessories to direct the light of fluorescent (and compact fluorescent) lamps. Boyce explains that smaller fluorescents need to be controlled carefully. “The T5 has a much smaller surface area than the T12 or T8. To get the same light output, the luminance of the lamp is going to be a lot higher, [resulting in] a much higher brightness,” he says. Reflectors minimize wasted light by reflecting and redirecting it down and out of the luminaire. However, illuminance uniformity may be affected.

What’s the story with daylighting?
Daylighting is defined as the sky’s contribution to illuminating indoor spaces, excluding direct sunlight. Natural sunlight has long been touted for its benefits to the work environment. At the same time, glare from windows is the bane of people working on computers. The secret to the daylight dilemma is diffused natural lighting. While direct lighting can impair vision and heat up a space, diffused sunlight connects end-users with the external environment and creates a comfortable environment to perform many tasks. “In a lot of open office environments, the wall partitions are placed really high. All the advantages of daylight in an open environment are taken away, because people are essentially in windowless spaces,” says Heerwagon. Facilities managers, architects, and interior designers need to work together to create spaces that achieve the maximum advantage of natural light.

The lighting environment includes window treatments and panel systems. Adds Heerwagon, “Better integration of interior design and facilities management with architectural solutions has to happen.” In some applications, giving end-users the ability to adjust window shading devices or using panel systems with windows can curtail complaints. Manual dimming controls, especially on the desktop, facilitates the use of natural light. “Lighting is sexy; it’s intimate. Lighting, unlike other systems, is something we are accustomed to interacting with,” says Rewers of MagneTek.

The use of photosensors to dim lighting can also prevent excessive brightness and reduce energy usage. Photosensors, unlike occupancy sensors, are electronic control devices that adjust the light output of a lighting system because of the detected illuminance in the area. Proper installation and placement, according to the LRC, have a tremendous impact on operation, energy savings, and end-users’ complaints. Testing sensors and following manufacturers’ guidelines translates into better performance. In combination with occupancy sensors, energy-efficient luminaires, and manual dimming controls, photosensors improve savings and the general environment.

Lamp technology innovation has issued forth a tremendous improvement in the quality of color and light. However, luminaires have also had a tremendous impact on the quality of lighting. Instead of static basic fixtures attached to office furniture, some furniture manufacturers are creating diffused light fixtures that work in concert with their workstations. The proper combination of task lighting and general or ambient indirect lighting can create a quality lighting environment. A Cornell University department of design and environmental analysis case study on the benefits of two-component lighting showed how task and indirect ambient lighting improved end-users’ perception of their environment.

A quality lighting environment is one where the end-users are satisfied and there is an absence of lighting-related health symptoms. The study also showed the importance end-users place on flexibility and the desire to control the brightness of their light environment. In open office space, this is usually achieved with task lighting. Conversely, in private offices, ambient and task lighting need to be adjustable. “I believe the industry is really listening to the voice of the customer; we’re giving the flexibility they need,” says Rewers.

How can a higher-quality lighting system save money?
Small improvements equal big savings. Bachner explains that if, in a 40-hour work week, employees are losing 26 seconds per hour due to the effects of poor lighting, a 1-percent improvement in productivity, due to a high-quality lighting system, will equal a 500-percent savings each year. This figure assumes an employee’s yearly salary of $25,000, including fringe benefits.

What’s on the horizon in lighting?
Ever since the first firefly was captured, there has been a search for light without heat. This promise of cool light is coming true with research on LEDs (light-emitting diodes), and their usage in signage, dim switches, and backlighting. Adds Rewers, “The industry needs to prepare the buyers for all the revolutionary changes that are coming.” Improvements in glass and plastic fiber-optics and LEPs (light-emitting polymers) are enabling light in challenging applications.

Computer and tabletop controls are also changing the face of commercial interiors. An industry initiative to increase awareness of lighting controls and fluorescent dimming products, the Rosemont, IL-based National Dimming Initiative (NDI), is striving to educate lighting professionals and building design firms. Through education, the NDI is promoting possibilities about the latest technologies.

At the same time, facilities professionals are recognizing how quality lighting in conjunction with overall good design redefines their buildings. Perhaps it’s no coincidence that the symbol for a bright idea is a lit light bulb — enlightened thinking about lighting is one of the brightest ideas there is.

Regina Raiford [email protected] is senior editor at Buildings magazine.
Jana J. Smith [email protected] is senior associate editor at Buildings Magazine.
Illustration by Rowan Enterprises.
Lighting Glossary

Color rendering index (CRI) —
a method for describing the effect of a light source on the color appearance of objects being illuminated, with a CRI of 100 representing the reference condition (and the maximum CRI possible). In general, a lower CRI indicates that some colors may appear unnatural when illuminated by a lamp.

Color temperature — see correlated color temperature.

Constant-wattage autotransformer (CWA) — the most common type of ballast used for HID lamps, it maintains a constant power (wattage) supply to the lamp when system input voltage fluctuates.

Correlated color temperature (CCT) — a description of the color appearance of a light source in terms of warmth or coolness, as measured on the Kelvin scale (K). As the temperature rises, the color appearance shifts from yellow to blue. Thus, lamps with a low CCT (3000K or less) have a yellow-white color appearance and are described as “warm”; lamps with a high CCT (4000K and higher) have a blue-white color appearance and are described as “cool.”

Ballast factor (BF) — the ratio of the light output of a lamp operated by a given ballast to the light output of the same lamp when operated by a reference ballast. Lamps operated by a ballast with a BF of 0.90 will provide 90 percent of their rated light output (lumens). BFs between 0.85 and 1.0 are the most common.

Disability glare — light that is relatively bright compared to the background, making vision measurably worse. The inability to see clearly as a result of the brightness of headlights from an oncoming car at night is an example.

Discomfort glare — the type of glare that is uncomfortable and distracting, yet less obvious than disability glare. A bright light source in an individual’s peripheral vision is an example.

Efficacy — the ratio of light output (lumens) to input power (watts), expressed in lumens per watt (LPW).

High-pressure sodium (HPS) — a high-intensity discharge lamp that uses sodium under high pressure as the primary light-producing element.

Illuminance — The amount of light that reaches a surface. Illuminance is measured in footcandles (lumens/square foot) or lux (lumens/square meter). One footcandle equals 10.76 lux, although for convenience the IESNA uses 10 lux as the equivalent.

Instant-start — a method of starting fluorescent lamps in which the voltage that is applied across the electrodes to strike the
electric arc is up to twice as high as it is with other starting methods. The higher voltage is necessary because the electrodes are not heated prior to starting.

Lamp life — the median life span of a very large number of lamps. Half of the lamps in a sample are likely to fail before the rated lamp life, and half are likely to survive beyond the rated lamp life.

Lamp lumen depreciation (LLD) — the reduction in lamp light output that progressively occurs during lamp life.

Lumen (lm) — a unit measurement of the rate at which a lamp produces light. A lamp’s light output rating expresses the total amount of light emitted in all directions per unit time. Ratings of initial light output provided by manufacturers express the total light output after 100 hours of operation.

Luminance — the photometric quantity most closely associated with the perception of brightness, measured in units of luminous intensity (candelas) per unit area (feet squared or meters squared).

Luminaire efficiency — the ratio of the light emitted by a luminaire to the light emitted by the lamp or lamps within it. A highly efficient luminaire emits most of the light that the lamp(s) emits.

Mercury vapor (MV) — a high-intensity discharge lamp type that uses mercury as the primary light-producing element.

Metal halide (MH) — a high-intensity discharge lamp type that uses mercury and several halide additives as light-producing elements.

Open-circuit voltage — the voltage applied across the output terminals of a ballast when no load is connected. This is the voltage applied across a lamp circuit to start a lamp. After starting, the voltage rapidly decreases and stabilizes at the operating voltage.

Preheat — a method of starting fluorescent lamps in which the electrodes are heated before a switch opens to allow a starting voltage to be applied across the lamp. With preheat starting, the lamp flashes on and off for a few seconds before staying lit.

Power factor — a measure of how effectively a ballast converts current and voltage into usable power to operate the lamps. A power factor of 0.9 or greater indicates a high-power-factor ballast.

Prismatic lens — an optical component of a luminaire that is used to distribute the emitted light. It is usually a sheet of plastic with a pattern of pyramid-shaped refracting prisms on one side. Most ceiling-mounted luminaires in commercial buildings use prismatic lenses.

Rapid-start — a method of starting fluorescent lamps in which the ballast supplies voltage to heat the lamp electrodes for one to two seconds prior to starting and, in most cases, during lamp operation. A rapid-start system starts smoothly, without flashing.

Reflected glare — often called veiling reflections, glare that results from light shining off polished or glossy surfaces.

Restrike time — the time required for a lamp to restrike, or start, after the lamp is extinguished. Normally, HID lamps need to cool before they can be restarted.

Visual comfort probability (VCP) — a system for estimating discomfort glare that predicts the percentage of people who are likely to find the lighting comfortable, against the percentage that find it uncomfortable.


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