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Energy Efficient Lighting

by David Nelson, AIA
David Nelson & Associates

Last updated: 07-23-2010

Introduction

Besides affecting the physical and emotional well-being of the building occupants, a building's interior lighting system is both a dominant consumer of electrical energy and a major source of internal heat. In the United States about one-quarter of the electricity budget is spent on lighting, or more than $37 billion annually. In commercial buildings it normally accounts for more than 30% of the total electrical energy consumed. Yet much of this expense can be avoided.

Specifying a high quality energy efficient lighting system that utilizes both natural and electric sources as well as lighting controls can provide a comfortable yet visually interesting environment for the occupants of a space. Recently developed energy efficient lighting equipment such as compact fluorescent lamps and "soft-start" electronic ballasts can be used to help cut lighting operational costs 30% to 60% while enhancing lighting quality, reducing environmental impacts, and promoting health and work productivity.

Description

To achieve a quality lighting environment, carefully choose the equipment to satisfy both performance and aesthetics needs. Lighting equipment selection should be based on a balance between the requirements of the design and an effort to limit the number of fixture types and lamp types in order to have reasonable maintenance inventories. Lamp selection is based on efficacy (lumens per watt), color temperature, color rendering index, life and lumen maintenance, availability, switching, dimming capability, and cost. For example, many T8 and T5 linear fluorescent and compact fluorescent lamps are excellent choices for today's buildings because they are energy efficient, have great color rendering properties, long life, and are readily available, easily controllable and very affordable. High frequency electronic ballasts are also important to visual performance because they reduce eyestrain and fatigue. Frequencies in the 20 kHz range and higher provide smooth, non-flickering lamp operation. Electronic ballasts are also responsible for better lamp performance, extending life and improving color characteristics. Luminaires are selected for their lighting effectiveness. This includes distribution characteristics, efficiency, quality of construction, aesthetics, and economics.

A. Energy Efficient Lamps Commonly Used Today

Energy efficient, fluorescent lamps

Energy efficient, fluorescent lamps

Fluorescent Lamps

Fluorescent Lamps are about 3 to 5 times as efficient as standard incandescent lamps and can last about 10 to 20 times longer. To gain the most efficiency, use current and proven equipment technology and install fluorescent luminaires in places where they can be integrated with the architecture, available daylight, and switching or dimming controls.

  • Linear fluorescent lamps T5HO lamps are now used in many high bay applications in place of H.I.D. lamps. These smaller diameter lamps have replaced the T12 lamps that have dominated the market for the past 30 years. These new lamps work well in luminaires that provide the general ambient lighting for a space. The long and diffuse nature of these lamps provides excellent surface lighting, and the smaller lamp diameters make for better optical performance in many luminaires. Indirect/direct linear fluorescent pendants and wall-mounted uplights are typical applications for these sources. Care must be taken to minimize direct views of extremely bright small-diameter lamps such as T5 and T5HO.
  • Compact fluorescent lamps (CFL) are often used as simple substitutes for incandescent lamps due to their significantly longer life and better energy efficiency. Self-ballasted, "screw-in" retrofit CFL lamps are sometimes used in the energy saving retrofit market. Also, retrofit lamps cannot be dimmed. However, the performance of screw-in lamps is usually not as good as the separate lamp and ballast combination. Due to their small size, CFL lamps are used in recessed luminaires, wall and ceiling mounted fixtures, and even track lighting and task lighting. The diffuse nature of the fluorescent lamp makes the CFL lamp a good choice for downlighting and wall lighting (also referred to as "wall washing").
  • Low mercury fluorescent lamps can be disposed of in landfills in some states. In these states, lamps that have sufficiently low levels must pass the testing procedure known as the Toxic Characteristic Leaching Procedure (TCLP) test (see EPA SW-846, "Test Methods for Evaluating Solid Waste (Physical/Chemical Methods)", Chapter 7, "Toxicity Characteristic Leaching Procedure," Section 7.4, page seven-2). However, many states have legislation pending that would not allow the disposal of any product containing mercury in a landfill. Specifying a low mercury product and then recycling that lamp at the end of its life offers the best environmental solution to disposal of mercury-containing lamps. There are many parts to a standard fluorescent lamp that can be recycled, including the glass, metal, mercury, and phosphor.
  • Inductive fluorescent lamps are white light sources with very good color rendering and color temperature properties. These lamps are energy efficient and offer extremely long life (over 100,000 hours), good lumen maintenance characteristics, and instant-on capability. The lamp enclosure is called a "vessel" and (shapes vary) coated on the inside with phosphor. Dimming is already available in Europe and will be available in the near future in the United States. They are powered by a small generator (about the size of a fluorescent ballast) attached to the lamp via a short fixed-length cable. The generator induces a current in the lamp which causes it to glow—there are no electrodes to wear out. The larger, diffuse nature of these sources makes them excellent for lighting larger volumes and surfaces. They are often used in place of low- to medium-wattage high intensity discharge sources because of the instant-on capability and reduced maintenance associated with the longer lamp life. This lamp source has promising application for indoor and outdoor lighting applications.

Fluorescent Lamp Links, Additional Educational Materials

Advanced Lighting Guidelines (ALG)
Federal Energy Management Program (FEMP)
New Buildings Institute, Inc.

High-Intensity Discharge Lamps (HID)

Different HID metal halide lamps

Different HID metal halide lamps.
Photo courtesy of sea-of-green.com.

High-intensity discharge lamps (HID) are still one of the best performing and most efficient lamps for lighting large areas or great distances. Metal halide (white light) lamps are replacing high pressure sodium lamps in many outdoor applications because white light sources can be 2 to 30 times more effective in peripheral visual detection than yellow-orange sources like high pressure sodium. Pulse initiated, or "pulse-start" metal halide lamps provide better color stability and longer life than previous technologies. PAR metal halide lamps with ceramic arc-tube enclosures are commonly used for accent lighting and highlighting in large spaces, and are now commonly used in retail applications. The small size of the metal halide arc-tube allows for excellent optical control. However, the extreme brightness of the metal halide lamp requires careful shielding and design.

Typically, HID lamps do not work well with occupancy sensors because most HID lamps take a long time to start each time they are switched off. Some HID lamps (called "hot restrike") are special in that they can be restarted immediately after being turned off, but if they are allowed to cool down, they will take about 15 minutes to warm up just like regular lamps. Special ballasts are available that allow the lights to be step-dimmed to 50% (or another level)—these ballasts could be used with occupancy sensors (the lights would be automatically dimmed to a set level when the room is unoccupied).

HID Lamp Links

Incandescent Lamps

Incandescent lamps are still used for accent and specialty lighting, where the warm color, controlled brightness, instant-on, and dimming capabilities of these sources is needed. Incandescent lamps can provide a "sparkle" that is not characteristic of more diffuse fluorescent sources. PAR and low-voltage lamps can provide good beam control, and if dimmed, can also provide a reasonable lamp life. 130V-rated incandescent lamps are also available which will last longer than their 120V counterparts when operated at 120V (with only slightly reduced light output for the same wattage rating). However, because of their lower energy efficiency and shorter lamp life, incandescent lamps should be used carefully for lighting of specific features. Some of the most effective lighting designs balance a small quantity of incandescent accent lighting with a fluorescent ambient (general) lighting system.

LED Lamps

LED lamps are the newest addition to the list of energy efficient light sources. While LED lamps emit visible light in a very narrow spectral band, they can produce "white light". This is accomplished with either a red-blue-green array or a phosphor-coated blue LED lamp. LED lamps last 40,000 to 100,000 hours depending on color. The current challenges of the LED source are a poor Color Rendering Index (CRI) of 65 or lower and poor efficacy, often less than 30 lumens per watt. LED lamps have made their way into numerous lighting applications including exit signs, traffic signals, under-cabinet lights, and various decorative applications. Though still in their infancy, LED lamp technologies are rapidly progressing and show promise for the future. For more information on LED lighting and other solid state lighting technologies visit the Department of Energy Solid State Lighting Web site.

LED light strips for under-cabinet lighting, for cove lighting, for shelf and cabinet interior lighting, and for edge lighting.

LED light strips for under-cabinet lighting, for cove lighting, for shelf and cabinet interior lighting, and for edge lighting.
Photo courtesy of The LEDLight.com

LED Lamp Links

B. Energy-Efficient Ballasts

Fluorescent Ballasts

  • Rapid start ballasts are the most common type of fluorescent ballast. These ballasts offer a long lamp life at a reasonable cost. They have been used for years with lighting controls to provide energy savings.
  • Instant start ballasts are usually the least expensive ballasts on the market. The efficiency of instant start ballasts is higher than rapid start ballasts, but lamp life is shorter, especially when the frequency of starts is increased due to the use of controls. They are often used where energy savings is the primary goal and lights are on continuously for very long periods of time. One advantage of the instant start ballast is that the lamps are wired in parallel, so that when one lamp on a multi-lamp ballast burns out, the others remain illuminated.
  • Program rapid start ballasts are some of the best to use for energy efficiency and long lamp life. These ballasts are slightly more expensive than standard rapid start ballasts, but use a "gentler" starting method so that frequent starting lessens the reduction in rated lamp life. These ballasts are recommended for smaller diameter fluorescent lamps and compact fluorescent lamps. With the right lighting controls scheme, program start ballasts can provide significant energy savings.
  • Dimming electronic ballasts for linear fluorescent lamps usually fall into two categories. The first type has a dimming range of 5% or 10% up to 100% light output and is generally the least expensive. This ballast is commonly used when the lowest light levels are not needed, or to achieve energy savings by dimming the lights when there is plentiful daylight. The second type of ballast, often referred to as an "architectural dimming ballast," is more expensive and has a dimming range of 1% to 100% light output. This ballast is used in situations where lower light levels are desired.

Electronic High-Intensity Discharge Ballasts

Electronic high-intensity discharge ballasts (HID) for metal halide lamps are now available for most lamps up to 150 watts. These ballasts should improve lamp performance and offer a limited range of dimming to achieve some energy savings.

Additional Ballast Information

C. Luminaires

Energy efficient luminaries with daylight dimming and occupancy sensors in office spaces at GSA Central Office.

Energy efficient luminaries with daylight dimming and occupancy sensors in office spaces at GSA Central Office.

A luminaire, or light fixture, is a unit consisting of one or more of the following components:

  • lamp(s) and lamp socket(s)
  • ballast(s)
  • reflective material
  • lenses, refractors, louvers, blades, or other shielding.

An efficient luminaire optimizes the system performance of each of its components. There are a few types of luminaires that offer opportunities for energy conservation in a lighting system design. Many of these provide indirect light to brighten the ceiling or are designed to brighten walls or task surfaces. Most of them are fluorescent and are easily controlled for further energy savings. Some examples are shown in the table below.

Type of Fluorescent LuminaireDescriptionBenefitsCautionsApplications
Indirect/Direct Linear LuminairePrimarily indirect, pendant or wall mounted, T8, T5 or T5HO lampingSoft, even illumination, good visual comfort, easily dimmedChoose spacing for good ceiling brightness uniformityHigh and low bay areas and classrooms
Indirect/Direct Decorative LuminaireTypically compact fluorescent or induction lampingSignificant energy savings, performance comparable to incandescentSelect diffuser for good brightness uniformity on glowing elementsSmall offices, lobbies, waiting areas, atriums, and corridors
Linear Strip LuminaireSurface mounted or pendant mounted with or without side reflectors, typically T8 lampingEnergy-efficient, small size, low-cost, easily dimmedBest when concealedIn coves or wall slots, on top of cabinets, stacks or lockers, and mechanical rooms
Task LuminaireLinear wall mounted "under shelf" or "arm type"Task lighting allows for lower ambient lighting levelsProvide appropriate task/ambient contrast ratiosAny task surface (desks, counters, workbenches, etc.)
Indirect Recessed LuminaireRecessed (light is directed up toward top of housing and reflected back down), typically 2' x 2' or 2' x 4', T8 or CFL biax lampingOptimized for fewer lamps than typical recessed lensed troffer luminaires, good visual comfortDoes not brighten ceiling, consider minor supplemental lighting (such as wall sconces)Corridors, open/private offices (can replace standard troffer in many applications)
Recessed Wall WasherLinear or round can-type, Linear or CFL lampingSignificant energy savings, performance better than incandescentBest when paired or in groups, choose spacings carefullySelect wall surfaces in many room types
Recessed DownlightRound can-type, CFL lampingSignificant energy savings, performance comparable to incandescentDoes not brighten the ceiling, can create light "scallop" on wallsLocalized infill lighting, often combined with other luminaire types
Wall SconcesWall mounted, decorative, CFL lampingSignificant energy savings, performance comparable to incandescentSelect diffuser for good brightness uniformity on glowing elementsLobbies, corridors, conference rooms, etc.

Application

Energy efficient lighting can be installed in new construction, modernization, and repair and alternation projects. It is applicable to all building types and space types, particularly educational facilities, office buildings, health facilities, research facilities, warehouses, libraries, and courthouses.

There are several programs in place to provide design guidelines and recognition for energy-efficient buildings. Many of these are government-supported.

  • Energy Star® Program: This program, supported by the U.S. Environmental Protection Agency (EPA) encourages energy-efficiency in new and existing commercial buildings. Participants, which in the past have included schools, retail and hospitality establishments, and industry and government facilities, are provided with guidance and support.
  • The Federal Energy Management Program (FEMP): FEMP promotes the conservation of energy and water, and the use of renewable energy sources by government agencies. FEMP is motivated in part by the January 24, 2007 Executive Order 13423, "Strengthening Federal Environmental, Energy, and Transportation Management" which calls for significant and quantified energy reductions in government energy consumption and greenhouse gas emissions. FEMP has established and encouraged industry partnerships, incentive programs, and educational opportunities which benefit the private sector as well.
  • U.S. Green Building Council Leadership in Energy and Environmental Design (LEED®) Building Rating System: LEED® provides developers and designers with guidelines and a checklist-type method for achieving high standards in sustainable building design. The system can also be used for calculating or improving the rating of an existing building.

Relevant Codes and Standards

Additional Resources

WBDG

Building / Space Types

Applicable and relevant to all building types and space types.

Design Objectives

Aesthetics, Cost-Effective, Functional / Operational, Historic Preservation—Update Building Systems Appropriately, Productive—Provide Comfortable Environments, Secure / Safe, Sustainable—Optimize Energy Use, Sustainable—Enhance Indoor Environmental Quality, Sustainable—Optimize Operational and Maintenance Practices

Products and Systems

Federal Green Construction Guide for Specifiers:

Project Management

Building Commissioning, Project Planning, Delivery and Controls

Federal Programs and Services

Organizations/Associations

Products Manufacturers and Suppliers

Publications

Others