Part 1: Basics of sustainable lighting
Within the newly established field of sustainable lighting design, lighting professionals are working with other building professionals to define a fundamentally different way to practice. Design team processes are more integrated than ever as the lines between the responsibilities of different disciplines blur.
Within the newly established field of sustainable lighting design, lighting professionals are working with other building professionals to define a fundamentally different way to practice. Design team processes are more integrated than ever as the lines between the responsibilities of different disciplines blur. The role of the lighting design professional has changed as more energy analysis, daylighting design, and visual quality research is performed.
Sustainable lighting design, as defined by the Illuminating Engineering Society of North America (IESNA) and International Assn. of Lighting Designers (IALD), is “meeting the qualitative needs of the visual environment with the least impact on the natural environment.” Achieving sustainability in lighting systems requires the systems to meet requirements from two worlds:
Have least impact on the natural environment
Meet the qualitative needs of comfort and acuity within the visual environment.
Part 1 of this article describes what is meant by least environmental impact and how to achieve it. Part 2, which will be published in a future issue, will describe the qualitative needs of the visual environment and how to achieve them.
Least environmental impact
The environmental impact of a product is best understood through a process called lifecycle assessment (LCA), which provides a method for evaluating the environmental burdens associated with the lifecycle of materials and services from “cradle-to-cradle” (see Figure 1). LCA produces quantitative data on 12 impact categories resulting from raw extraction, production, use, and recycle and/or disposal of a product or system:
Criteria air pollutants
Fossil fuel depletion
Indoor air quality
Efforts are being made to incorporate LCA metrics into the U.S. Green Building Council (USGBC) LEED rating system, but this will take some time because there is not yet consensus on environmental performance metrics for lighting equipment.
Many lighting professionals associate environmental impacts only with the period of time when products are in use, primarily because energy considerations are so dominant in lighting. However, it is important to consider impacts from all phases of a product's lifecycle when assessing environmental impact. For example:
What are the impacts of producing luminaire housings, reflectors, lenses, and packaging?
Is a low iridescent specular coating more environmentally harmful than a simple diffuse white coating?
Are the manufacturing processes used to produce an LED more or less harmful to the environment than producing an incandescent lamp?
What happens to the product at end of life?
Is an extruded aluminum housing environmentally more friendly than a steel housing?
What are the implications of an electrostatic painting process versus an anodizing process?
Are there environmental impact differences between using recessed troffers versus pendant indirect/direct luminaries?
Designers should ask manufacturers new questions related to products. (See sidebar, “New questions to ask about products,” page 20.)
Lamp manufacturers have been steadily reducing the amount of mercury in energy-efficient lighting products to minimize contaminating waste streams. Lead is being eliminated from glass used in lighting and from solders used in luminaires, lamps, ballasts, and solid-state technologies. The reduction of toxic materials in lighting systems will reduce the toxic material content of buildings, which will in turn clean up the waste streams of buildings being renovated or demolished.
Meanwhile, disposal issues need to be taken into consideration for lighting system lifecycles. The proper means of disposal of luminaires varies according to the materials they are constructed with. Ballasts, fluorescent lamps, high-intensity discharge lamps, and batteries are all treated differently. The Resource Conservation and Recovery Act (RCRA) is a federal regulation for waste disposal, and states have individual regulations as well. The U.S. Environmental Protection Agency's municipal solid waste data website, www.epa.gov/msw/states.htm , has information and hyperlinks to regulations and contact information for each state.
LEED encourages the use and specification of products with recycled content. Various regions have evaluated the inclusion of waste restrictions for specific products (such as electronic equipment) or hazardous materials in products. To date, no regulations in North America include lighting equipment. The National Electrical Manufacturers Assn. is taking steps on an aggressive time schedule to eliminate hazardous materials in lighting products or to establish maximum levels of content where no acceptable alternatives exist. For more information, visit tinyurl.com/NEMAhazard .
Energy efficiency and conservation
According to the Energy Information Administration, lighting accounts for 44% of electricity use in U.S. commercial buildings ( www.eia.doe.gov ). Cutting wasted electricity consumption by proper lighting design and control has ancillary environmental benefits of avoiding power plant emissions, reduced extraction of natural resources, and reducing operating costs associated with replacing luminaires.
Minimizing energy use combines energy-efficient lighting fixtures with the conservation of energy by turning lights off when not in use. Guiding or mandating efficiency and conservation are energy codes, LEED rating systems, good design practice, numerous guidelines, and publications from government agencies, not-for-profit organizations, and articles appearing in trade publications.
Lighting unavoidably uses energy, but new technologies and lighting design techniques have greatly diminished energy use in new and renovated buildings. There are many good resources for developing strategies to minimize energy use. (See sidebar, “Engineering resources for lighting,” page 22.)
Also, ASHRAE/IESNA Standard 90.1 and state energy codes have gone a long way toward mandating good efficiency measures. The new (2010) ASHRAE/IES/USGBC Standard 189.1, “Standard for the Design of High Performance, Green Buildings Except Low-Rise Residential Buildings,” is a code-language standard ostensibly leading to whole-building designs that achieve energy savings 30% below energy code.
The LEED 2009 rating system has prerequisites and credits that pertain to lighting. Lighting relates indirectly or directly to up to 40 credits in the LEED rating system, most of which are tied to energy savings that relate to ASHRAE/ANSI/IESNA 90.1-2007, including:
Light pollution reduction
Minimum energy performance and optimum energy performance
Controllability of systems—lighting
Daylight and views—daylight
Daylight and views—views
Read the sidebar, “LEED and lighting,” on page 21 for more detail about the credits and perquisites.
For LEED—Existing Buildings (O&M), lighting-related elements include lamps with minimum consumption of mercury (less than 100 pico-grams per lumen-hour) and lamp recycling (combined with other recycling). Lighting energy efficiency also contributes to the LEED EB O&M requirement that the building demonstrate it has achieved an EPA Energy Star score (or equivalent) of at least 69.
Maximizing energy efficiency
Saving energy means reducing the input power of a system, the time the system operates, or both. System input power can be reduced through appropriate system design approaches, such as:
Select the lower end of IESNA Handbook recommended lighting levels, thereby increasing task contrast
Light vertical surfaces, which provides a more pleasant environment
Install lighting only where it is needed
Provide task/ambient systems for high ceilings and recessed indirect systems for low ceilings
Use automatic controls
Tune a lamp system to the designed target illuminance by tailoring lamp output through ballast factor
Select proper lamp and luminaire system combinations.
While T8 lamps with electronic ballasts are commonly used for linear fluorescent approaches, new generation “high-performance” T8 or T5 systems provide better energy savings. In the example shown in Table 1, a standard three-lamp T8 parabolic system is compared to a new generation two-lamp T5 system. Approximately 30% energy savings can be realized by this lamp/luminaire combination.
While reducing input power reduces one side of the equation, applying effective lighting controls affects the other side of the equation—the time a system operates. Today many energy codes require some form of automatic lighting control for spaces occupied less than 24 hours. Manual, automatic, and “intelligent” lighting controls all provide significant opportunities for energy savings. Some control methods are:
Occupancy sensors: Occupancy sensors use passive infrared, ultrasonic, or dual-tech technologies to sense when the space becomes unoccupied and automatically turn off lights after a settable time delay. For daylit areas, manual ON type switches are recommended for reduced lamp cycling.
Multilevel switching: Multilevel switching is sometimes considered an economical approach to dimming. The concept is that groups of luminaires or individual lamps in each luminaire are controlled together to achieve different light levels.
Programmable lighting control systems: Centralized light control systems provide a way to combine several lighting control strategies—occupancy sensors, daylight harvesting, photocell, or time schedule. These systems can take the form of relay-based panels or be integrated into panel boards using programmable circuit breakers.
Daylight harvesting: Daylight harvesting can be open- or closed-loop systems. Open-loop systems monitor exterior daylight levels and adjust interior lights without regard to measured interior light levels. Closed-loop systems monitor interior light levels in daylit areas and adjust lighting to meet a target illuminance level. One method of controlling daylighting is with electronically actuated mechanical shades. The shades can be raised and lowered according to schedules, lighting levels photo sensor response, or by occupants using manual overrides.
Intelligent systems: Intelligent lighting uses bi-directional communication between control and luminaire. The control intelligence resides in the ballasts, each of which is uniquely addressable. As a result, control communication is independent of power circuits. This eliminates the need for dimming and/or relay panels and the home runs from the load to these panels.
The application of intelligent lighting maximizes energy and cost savings while optimizing performance and the quality of the visual environment. Through the tools of the intelligent lighting, the designer can provide a dynamic lighting system, responsive to the architecture and the users of the space. A significant amount of energy savings can be realized by having different control strategies.
There's a rule of thumb that about 1 W of HVAC cooling load savings will result from every 3 W of lighting savings (Figure 2). This is more typical in Southern states. Several variables—like environmental, building, system type, economic—need to be considered to precisely determine the savings. (See the Lighting Design Lab website at www.lightingdesignlab.com for a thorough discussion.)
Wireless communication and power uses two-way radio frequencies to control lighting systems to provide system flexibility, control, and integration. Wireless mesh networks allow luminaires to talk to each other, enabling them to automatically reconfigure in response to different occupancy patterns, daylight changes, or peak-load. Some wireless lighting controls scavenge power from the mechanical operation of toggle switches, enabling designers and occupants to place light switches wherever they are easiest to use. This makes occupants more likely to turn off lights when they are not in use.
Extending service life
Durability and maintainability are critical for long-term performance, and are often overlooked as sustainable features of products. Obviously, the selection of fixtures made from materials appropriate for the intended use (i.e., for exposure to weather, ocean air, industrial pollutants, safety) is one aspect of durability and maintainability. But design also plays a critical role. Fixtures should be selected and located where lamps can be easily and safely replaced. Use of tall ladders, scaffolds, and lift buckets should be avoided wherever possible. Minimizing the quantity of different lamp types makes maintenance simpler and less expensive. If lights are too difficult to maintain, they won't be.
Another factor is system flexibility. If the lighting system can be moved, added onto, made smaller, etc., as occupancy changes, the system will be more sustainable. Flexibility is enhanced by having modular lighting and flexible wiring. These systems minimize the amount of wiring, reducing the amount of waste from damaged ceiling tiles and abandoned electrical conduit and conductors that are generated during remodels.
Simplicity of controls is another factor for durability and maintainability. If controls systems are too complex, they will lead to higher energy and services costs, and they ultimately will be replaced by simple on/off switches. Designers should consider:
• Complexity of the system
• Number of components
• Facility monitoring and reporting
• Ease of system configuration
• Ease of maintenance
• Availability and ease of replacement of components.
Table 1: T8 versus T5
Generic parabolic T8 system compared to high-performance T5 system for standard 8 ft by 10 ft spacing.
Lamps per fixture
Power density (W/sq ft)
Source: Jim Benya, Benya Lighting Design.