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L A B O R A T O R I E S F O R T H E 2 1 S T^ C E N T U R Y :
B E S T P R A C T I C E G U I D E
E FFICIENT E LECTRIC L IGHTING IN L ABORATORIES
Introduction by researchers. In addition, the lighting energy intensity
There is a considerable body of research that describes in laboratories is up to twice that of a typical office space. the impact of the visual quality of the work environment Lighting energy use typically accounts for between 8% on worker comfort, health, and productivity. The appro- and 25% of total electricity use, depending on the percent- priate design of lighting systems is especially important in age of lab area (see Figure 1). While not a significant per- laboratories, given the intensity and significance of work centage compared to HVAC systems, it nonetheless carried out in laboratories and the long work hours spent provides several opportunities for energy efficiency.
Lighting Energy Use in Laboratories (% of Total Electricity Use)
Facility ID
Figure 1. Data from the Labs21 Energy Benchmarking database indicates that lighting energy varies from about 8% to 25% of total electricity use in most laboratory facilities.
United States U.S.^ Department of Energy Environmental Energy Efficiency and Renewable Energy Protection Agency Federal Energy Management Program
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This best-practice guide is one in a series created by the Laboratories for the 21st^ Century (“Labs21”) program, a joint program of the U.S. Environmental Protection Agency and U.S. Department of Energy. Geared towards architects, engineers, and facility managers, these guides provide information about technologies and practices to use in the design, construction, and operation of safe, sus- tainable, high-performance laboratories. The intent of this guide is to highlight and summarize best practice strategies for high-performance, energy-effi- cient lighting in laboratories. This guide is not intended to serve as a general guide on how to design lighting for a laboratory. Comprehensive “how-to” information on light- ing design can be found in the Illumination Engineering Society of North America (IESNA) handbooks as well as other resources listed in the references. The next section describes best practice strategies for systems and components (fixtures, lamps, controls). The section following that describes the best practices pertain- ing to lighting performance parameters (illuminance lev- els, color rendition, etc.).
Systems and Components
Daylight Integration
Strateg y #1: Electric lighting should al ways be designed as a supplement to daylighting. Whenever feasible, use natural light as the primary daytime light source. It is the most visually effective and energy-efficient source of lighting. The National Institutes of Health (NIH) guidelines state, “Laboratories and offices shall be provided with natural light and views to the out- side, as long as they do not conflict with functional requirements.” Although this guide is specifically focused on the design and operation of electric lighting systems, it is well understood that the integration of any electric lighting sys- tem is only a part of an overall lighting design scheme that includes daylighting and significant integration with mechanical systems. The overall lighting design must also acknowledge the psychological stimuli that light presents to most living things and reinforce, rather than conflict with, physiological conditions such as human circadian cycle entrainment. The intensity of light, light source color, and controls can all play a key role in satisfying both phys- iological and psychological needs. The Labs21 Daylighting Best Practice Guide provides design guidance and examples of how to effectively use daylighting in laboratories and integrate it with electric lighting.
Fixture Configuration
Strateg y #2: Use direct-indirect ambient lighting parallel to benchtop. There are two primary aspects of the ambient lighting fixture configuration in a laboratory:
- Beam direction: direct, indirect, or direct/indirect.
- Fixture location relative to bench top: parallel, perpen- dicular, or other. While there is no single “best” fixture configuration, a direct-indirect configuration oriented parallel to the bench is, typically, the preferred option. (A notable exception to this guidance would be laboratories that require wash- down capabilities.) Direct-indirect fixtures direct a certain percentage of the light upwards and the remainder downwards, thereby capturing the advantages and minimizing the disadvantag- es of both components. A 100% direct fixture is more effec- tive in producing high illuminance levels at the benchtop, but also more likely to produce glare, high contrast ratios and shadowing, and poor vertical brightness. Because indi- rect lighting reduces shadowing, it often requires a lower level of illuminance than would direct lighting to perform tasks equally well (Watch 2001, p. 225). On the other hand, while a 100% indirect fixture minimizes glare and shadow- ing, the lack of any direct component creates an impression of dullness, even if illuminance levels are adequate. In labs, the direct component should preferably be between 20% and 40%. Figure 2 shows two typical direct/ indirect lighting system installations located parallel to the benchtop and directly above the front edge of the benchtop. An alternative to placing lighting fixtures directly above each benchtop is to place them between benches. This placement usually necessitates primarily indirect light- ing to avoid shadowing at the bench. The advantage of this approach is reduced lighting power density. For example, at the U.S. EPA’s Research Triangle Park Facility, this approach (Figure 3) allowed power density to be reduced from 1.85 W/sf to 1.35 W/sf, providing an estimated annu- al savings of over $200,000. The first cost premium was about $200,000, resulting in a simple payback of about one year. To make indirect lighting efficient, the ceiling should have at least 80% reflectance, and walls should have 65% or greater. Ceiling height is an important consideration. Fixtures should be located at least 18 to 24 inches below the ceiling to avoid hot spots (although there are some new luminaire designs that allow for shorter suspension lengths). This mounting recommendation is especially true for T5 technology, primarily because the high lumen output
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Figure 4: Mock-up of a lab module for Memorial Sloan Kettering Cancer Center, showing bench-mounted ambient lighting with under-cabinet task lighting. Source: ZGF Architects.
Figure 5: Aisle-mounted indirect luminaires suspended in relation to the overhead service trunk can maintain good- quality lighting regardless of the position of the movable benches, as long as the ceiling remains somewhat consistent.
Figure 6 shows a fixture configured around vertical ser- vice trunks. This allows benches to be located along two perpendicular horizontal axes, thereby affording even more flexibility. Physical mock-ups are an effective way to study dif- ferent lighting configurations for a lab module. The mock-
Figure 6: Conceptual study of a lighting array incorporated within the electrical, data, gases overhead service trunk. This scheme provides good lighting for benches located either parallel or perpendicular to the service trunks. Source: Flad Associates and Pivotal Lighting Design/ Affiliated Engineers.
up should include, as a minimum, a sample installation of the proposed ceiling material as well as any mechanical diffusers or other ceiling elements that are likely to be within the beam spread of the indirect portion of the light- ing system distribution pattern. An actual lab bench, fitted out with full-height shelving as specified, will provide very revealing clues about how the visual environment is shaped with these elements. Strateg y #4: Use task lighting. The various types of tasks carried out in a laboratory often have different lighting requirements. Separating task and ambient lighting allows for greater user flexibili- ty and energy efficiency. Consider using articulated-arm task lighting for maximum flexibility in meeting user needs. If this cannot be done, then consider under-cabinet task lighting (see Figure 7). However, the heat generated from under-cabinet task lighting may limit the types of chemicals stored on the shelf directly above the task light. Under-cabinet task lights also require that the space below the task light be free of clutter and storage that could potentially block the light. It is important to ensure that task lighting is explicitly integrated into the overall light- ing design early in the design process. Energy efficiency is achieved by reducing ambient light levels (e.g., 30 fc) and ensuring that task lights are turned off when not needed. If task lighting is seen as an optional supplement to ambi- ent lighting (e.g., as part of furniture and finishes), design- ers will likely configure ambient lighting to meet task requirements, negating the energy efficiency benefits of separating task and ambient lighting, and reducing its overall cost-effectiveness.
Figure 7. Under-cabinet task lighting in a USDA laboratory. Source: HOK.
Lamps and Ballasts
Strateg y #5: Use energ y-efficient lamps and ballasts.
Over the past two decades, significant progress has been made in efficiency improvements to lamps and bal- lasts, and they are one of the most cost-effective measures for improving energy efficiency in buildings. Many publi- cations, some of which are listed at the end of this guide, provide comparative analyses of lamps and ballasts. Figure 8 summarizes the range of efficiencies in terms of lumens per watt, which is the primary measure of lamp efficacy. It is interesting to note that daylight, in addition
Standard Incandescent Tungsten-Halogen
Mercury Vapor Compact Fluorescent
Linear Fluorescent Metal Halide
High Pressure Sodium
Daylight w/ Direct Sun Daylight w/o Direct Sun 0 50 100 150 200 250 300 350 Lumens per Watt of Heat Gain
Figure 8. Luminous efficacy of various light sources. Daylight ranges calculated inside of single-pane clear and high-performance glass. Data source: Advanced Lighting Guidelines.
to all its other benefits, is also the most efficacious light source. Efficacy can be evaluated on at least three levels:
- Lamp efficacy – which compares the efficacy of differ- ent lamps, without considering ballasts.
- Combined lamp and ballast efficacy – which includes ballast losses.
- Luminaire efficacy – which considers the efficacy of the luminaire system within the context of architectural space. Efficacy metrics can be obtained from manufacturers and other resources. Some lamp and ballast considerations that apply specifically to laboratories include the follow- ing:
- Consider the use of T5 lamps in new construction. The smaller lamp size translates to smaller and sleeker luminaire designs and can yield far better optical con- trol and greater luminaire efficiency, compared to T8s. T5s are also better in terms of reduced material use, consuming 60% less glass and phosphor material, and up to 50% less packaging when compared to T12 lamps (Yancey 1998).
- Always use electronic ballasts. In instrument labs where standard electronic ballasts and lamps may interfere with instrument operation, use radio- frequency-shielding luminaires. Alternatively, consider using light pipes or fiber-optic cables to provide light- ing from a remote source.
- Always use compact fluorescent (CFL) or low wattage ceramic metal halide lamps instead of incandescent; the newer CFL and halide lamps have addressed color ren- dition issues.
- For fume hoods and bio-safety cabinets, which usually have their own lighting, coordinate the lamp color and type with the manufacturer to ensure compatibility with the overall visual environment requirements.
Controls
Strateg y #6: Use daylight controls for ambient lighting in perimeter zones. One of the major benefits of daylighting is the ability to save energy by reducing the use of electrical lighting by dimming or switching. The cost-effectiveness of daylight- based dimming is a function of electricity prices and the cost of dimming systems. One way to improve cost-effec- tiveness is to right-size the HVAC system by accounting for the reductions in cooling load that result from lower internal heat gains achieved by reducing electrical lighting
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Strateg y #12: Don’t overdesign. Carefully assess required illuminance levels in conjunction with other performance parameters.
While designers have traditionally focused on the required illumination levels for a space, there are several other aspects of lighting design that significantly affect visual performance and the overall visual perception of the space, as will be discussed later. Therefore, it is impor- tant to recognize at the outset that illuminance require- ments must always be considered in conjunction with other visual performance parameters. For example, the “see-ability” of 50 to 70 footcandles (fc) of indirect lighting is comparable to 100 to 130 fc of direct lighting, due to the elimination of glare with indirect sources (Doberdruk 1999). Thus, “qualitative” factors directly affect lighting energy use.
The 9th^ edition of the IESNA Handbook has revised its illuminance recommendations for laboratories downward from the previous edition, as indicated in Figure 9. Many owners of laboratory facilities are questioning traditional- ly conservative engineering practices, which frequently led to significant over-sizing of basic building services,
Figure 9. A comparison between the IESNA laboratory illuminance recommendations in the current (9th) edition and the previous (8th) edition. Data source: IESNA.
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costing owners more money for both construction and ongoing operation. There are no universally applicable standards for illu- minance in laboratory spaces. While there may be a need to light a specific task to between 80 and 100 fc, it is rarely necessary to light the whole laboratory to that level. In fact, high illuminance levels may reduce visual acuity for tasks that require reading monitors and other electronic displays. Therefore, the lighting designer should carefully assess illumination needs based on the task. If flexibility is required, then incorporate appropriate strategies to vary the light levels. For example, a design guideline devel- oped for a University of California laboratory advocated a flexible configuration which had 30 to 50 fc of ambient lighting, with additional illuminance provided by under- cabinet task lighting, and a re-locatable articulated-arm task light in a few locations for high-illuminance tasks.
Brightness, Uniformity and Other Qualitative
Factors
As noted earlier, visual acuity is a function of several factors beyond illuminance levels. The 9th^ edition of the IESNA handbook lists 23 criteria, including color appear- ance, direct glare, and surface light distribution. The resources at the end of this guide provide more informa- tion on these factors. Some important considerations for laboratory spaces are discussed below.
Strateg y #13: Balance brightness of walls, ceiling, floor, and work-surfaces. Balanced vertical illumination in the field of view reduces contrast, enhancing visual acuity. This can be achieved using wall-washing with down-lights on perim- eter surfaces. No other surface in a typical room will contribute more to the distribution of light than the ceiling. To aid in the proper distribution of light, a white or nearly white ceiling is recommended, with a minimum reflectance value between 0.80 and 0.85, as noted earlier. A matte finish is preferred over a semi-gloss or semi-specular finish because it eliminates the possibility of reflecting the images of bright light sources from within the indirect component of luminaires. Any color or tint present in the ceiling material will also be contained in the light reflected off that surface, so care is needed in specifying any finish other than white or near white. Floors have more to do with contrast reduction in the visual field than with contributing significantly to the ambient light level in a room. The reflectance value of a cream-colored tile is 0.45, while a dark brown floor has a reflectance value of 0.1. These two color choices will create
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Figure 10: Balance of surface brightness in this lab is achieved with energy-efficient recessed lab lighting using T8 technology and compact fluorescent down lights with 4100-K lamp color. Photo courtesy of Pivotal Lighting Design/Affiliated Engineers.
significantly different impressions of brightness, even though the calculated illuminance levels will be almost identical. Finally, dark bench tops and reagent shelves with mis- cellaneous items contribute to an impression of overall lower brightness even though the design meets the target luminance at the bench. Dark bench tops should therefore be avoided, if possible. Strateg y #14: Select lamps with high CRI and optimal color temperature. Improved color rendition of the ambient lighting sup- ports greater visual acuity, saving energy by allowing lower illuminance levels. Higher color-rendering T8 and T5 light sources are also more compatible with daylight and with most compact fluorescent lamps. Specify fluores- cent light sources with a minimum CRI of 82. Where color rendition is very critical (e.g., analysis of blood specimens and organ tissues), consider the use of 5-phosphor or full spectrum lamps. Typically, for laboratories, a color temperature of 4100-5000K is recommended. It is important to coordinate the color temperature of ambient and task lighting, since differences can be visually distracting. Strateg y #15: Balance uniformity and variation. There should be a balance of light between benches, aisles and room perimeters. It is important that luminaires
provide wall brightness at the tops of walls, to avoid the “cave” effect. This is especially important in labs, because top shelves are often used for storage (even though code stipulates that nothing should be within 18 in. of the ceiling). While a reasonable amount of uniformity is important, it is also important to have some visual variation and inter- est (e.g., accent lighting with wall sconces), otherwise the space will appear dull. Totally indirect lighting systems can often provide a virtually shadowless visual environ- ment. By flattening perspective within the evenness of sur- round-lighting, this lack of direct-light emphasis presents the three-dimensional lab and its accompanying apparatus to the eye as a mere two-dimensional visual task. Bench- mounted adjustable task lighting can help to enhance the visual environment significantly by adding sparkle and revealing 3D form. This adds variation and visual interest, which, in turn, support visual acuity.
Maintenance
Lighting system maintenance should be addressed beginning with the actual luminaire specification. Newer lamp technologies with reduced physical size have driven the design of sleeker, smaller luminaires. These have become correspondingly harder to physically maintain than larger versions simply because appropriate clear- ances between lamps, reflectors and luminaire housings are often forsaken for aesthetics. It is the lighting design- er’s responsibility to specify lighting fixtures that are clear- ly well-constructed and assembled with maintainability in mind. Accessories to avoid are those that require special tools to remove or that complicate routine maintenance procedures, such as clipped-on external baffles or louvers with sharp edges that snag dust cloths.
Codes and Standards
The IESNA Lighting Handbook is the primary refer- ence for illumination criteria. Some of the energy efficiency requirements for laboratory lighting found in codes and standards include the following:
- ASHRAE Standard 90.1-2004 specifies lighting power densities for various space types. Laboratories are lim- ited to 1.4 W/sf.
- California Title 24 (2005) limits lighting in high-preci- sion work environments to 1.3 W/sf.
- The 2004 Seattle Energy Code limits lighting in labora- tories to 1.8 W/sf.
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References and Resources
Advanced Lighting Guidelines, 2003 Edition. New Buildings Institute, Inc. David, Victoria. “Lighting Considerations in Lab Planning and Design” The Lab Design Handbook 2004. Published by R+D Magazine. Doberdruk, Michael. 1999. “Three bright ideas for select- ing laboratory lighting,” Laboratory Design vol. 4, no. 12, December 1999. IESNA Lighting Handbook, Reference and Application. 9 th^ Edition. Rea, M. (ed). Illuminating Engineering Society of North America. 2000. Lighting Research Center, Rensselaer Polytechnic Institute. http://www.lrc.rpi.edu/ Labs21, Daylighting in Laboratories Best Practice Guide. http://www.labs21century.gov/pdf/bp_daylight_ 508.pdf Losnegard, J. 2004. “Best Practices in Laboratory Lighting Design” Laboratory Design, October 2004, Vol. 9, No. 10. NIH Design Guidelines. http://des.od.nih.gov/eWeb/ policy/html/policy-index.html Watch, Daniel. Research Laboratories. Wiley. 2001. Yancey, K. 1998. Fluorescent Lamps + Electronic Ballasts: Less is More. Consulting Specifying Engineer 23 (2): 56-60.
Laboratories for the 21st Century U.S. Environmental Protection Agency Office of Administration and Resources Management www.labs21century.gov
In partnership with the U.S. Department of Energy Energy Efficiency and Renewable Energy Bringing you a prosperous future where energy is clean, abundant, reliable, and affordable
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Prepared at the Lawrence Berkeley National Laboratory A DOE national laboratory
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Ackno wledgements
Authors: Kenneth Kozminski, LEED AP, Affiliated Engineers, Inc. Stuart Lewis, AIA, HOK - Science + Technology Paul Mathew, Ph.D., Lawrence Berkeley National Laboratory Reviewers: Nancy Carlisle, National Renewable Energy Laboratory Sheila Hayter, P.E., National Renewable Energy Laboratory David Nelson, AIA, IALD, David Nelson & Associates
For More Information
On Efficient Electric Lighting in Laboratories: Paul Mathew, Ph.D. Lawrence Berkeley National Laboratory 901 D. Street SW, Suite 950 Washington DC 20024 voice: 202-646- email: PAMathew@lbl.gov On Laboratories for the 21 st^ Centur y: Dan Amon, P.E. U.S. Environmental Protection Agency 1200 Pennsylvania Ave., N.W. Washington, DC 20460 202-564- amon.dan@epa.gov
Will Lintner, P.E. U.S. Department of Energy Federal Energy Management Program 1000 Independence Ave., S.W. Washington, DC 20585 202-586- william.lintner@ee.doe.gov
Best Practices Guides on the Web:
www.labs21century.gov/toolkit/bp_guide.htm
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