Integrating Lighting and Daylighting (Continued from p. 116 of the November 2009 issue of BD+C)
Then, when sitting down to put together those control specs, Building Teams should consider the following punch list from RPI’s Smith offers:
• Select the appropriate type of control for space—for example, switching vs. dimming.
• Determine the type and location of fenestration, and occupant interaction with blinds or shades, such as open-loop vs. closed-loop system.
• Calculate the number of control zones as dictated by fenestration size, space size, and required light levels.
• Establish the range of response, spectral response, spatial response, speed response, and time-delay adjustment.
• Determine the number of ballasts each photosensor can control.
• Make sure that the photosensors and ballasts are compatible.
Closed-loop systems are more in tune to the interior lighting levels as they are calibrated to maintain a specific set point and will adjust the dimming accordingly. However, closed-loop systems cannot distinguish between daylighting changes and occupant interference. Furthermore, when renovations to a space—such as repainting or new carpeting—change the lighting dynamics, the set point and dimming steps need to be recommissioned, which can be costly.
The California Lighting Technology Center, in Davis, is combining both types of systems into one, a self-commissioning dual-loop sensor dimming system. In addition to distinguishing between daylight and interference, the system constantly updates itself by using daily measurements of electric light levels and establishing a set point and dimming curve accordingly. CLTC is currently working with a manufacturing partner to commercialize the technology, and a big-box retail store is demonstrating the commercial prototypes. (For more information, see: www.cltc.ucdavis.edu.)
Another recent development is LRC’s self-commissioning photosensor. Utilizing digital controls, the wireless photocell is entirely contained within a control box that fits inside a standard light-switch mounting box. The Lighting Research Center says the system can help reduce installation costs and performs self-commissioning in just two minutes’ time.
Once the decision has been made as to the type of photosensor to be u sed, the next technology decision is the choice of ballast type. There are two main types: voltage-reducing ballasts and dimmable ballasts. Each can be used to dim a group of fixtures. Voltage-reducing ballasts utilize either a transformer to curtail the voltage traveling to the ballasts, or electronic controls to alter the electricity’s waveform. (In some cases, the use of electronic controls may adversely affect building power quality.) New technologies are better enabling ballast dimming, according to experts from Washington State University’s energy program (www.energy.wsu.edu). Dimmable ballasts typically operate via control wiring, which is separate from the power wiring. While they usually use low-voltage wiring, dimmable ballasts can operate on line voltage as well. In either case, dimmable ballasts can be very energy efficient.
DAYLIGHT HARVESTING AND ADVANCED CONTROLS
Yet another related development is the rise of systems for daylight harvesting. This technology capitalizes on peak-demand reduction in a more cost-effective manner than traditional dimming systems, which have additional equipment and commissioning expenses.
An example is the Simplified Daylight Harvesting system, developed by CLTC and now commercially available, which consists of a photosensor to measure light levels, relays to switch the electric lights, a controller that determines when to change the lighting, and an optional occupancy sensor. According to a technical brief from the California Energy Commission’s Public Interest Energy Research Program (http://www.esource.com/esource/getpub/public/pdf/cec/CEC-TB-36_Daylighting.pdf), the system enables users to set their own on and off set points, and the technology accounts for interior changes—furniture layouts, interior surface reflectance, and the like¯as well as adapting to decreasing electric light levels as lamps age.
More sophisticated systems for lighting controls offer high levels of intelligence and interoperability with other buildings systems. Because the lighting controls market largely consists of individual components such as ballasts, switches, and controls, these products often don’t function optimally as a system, especially when supplied by different manufacturers. To address this problem, LBNL is now developing an Integrated Building Environmental Communications System, or IBECS (www.lighting.lbl.gov/IBECS/ibecs.html). By utilizing embedded device networks, IBECS essentially optimizes lighting control system interoperability and enables the system to communicate with and control individual light fixtures.
OPTIMIZING ELECTRICAL LIGHTING
Regardless of controls approach, anytime the Building Team is integrating daylighting with electric lighting, it is important to follow established best practices for maintaining an effective system.
One vital area is balancing ambient lighting with task lighting. “Daylight that consistently enters the space generally provides ambient lighting,” explains LCA’s DiLouie. Consequently, the task lighting (and accent lighting, if called for) is then accounted for by the electric lighting design.
| Lighting Designers Step into the Limelight Recognizing that an integrated design approach is essential when designing a high-performing, energy-efficient daylighting and lighting system, the lighting designer must be brought in early as a key player. “The role that a lighting designers plays on the building team is paramount to the success of the building,” says Matthew Tanteri, IES, an educator with the International Association of Lighting Designers and principal of Tanteri + Associates, Irvington-on-Hudson, N.Y. Aaron Smith, a senior research specialist at Rensselaer Polytechnic Institute’s Lighting Research Center, says, “The lighting designer can drive many decisions that affect building form, equipment, and performance.” By bringing this professional on board before orientation and building form are determined, the daylighting design can be properly analyzed as part of the optimal lighting solution, says Tom McDougall, PE, Assoc. AIA, vice president with the Weidt Group, Minnetonka, Minn. Richard King, AIA, a senior associate with RMJM, Philadelphia, says, “Lighting specialists are critical to the process, bringing knowledge of both natural and artificial light in order to find the best solution for both.” Lighting designers bring are also able to fuse light and architecture with site and program, notes Tanteri. “They are ultimately responsible for how the building is visually experienced during day and night and for bringing value to the materials, surfaces, and spatial environments contained within the building,” he says. Lighting designers achieve this fusion, says McDougall, by determining ambient, task, and accent lighting needs, and then specifying fixtures and lamps. In sum, the lighting designer’s role is to maximize user comfort, optimize energy savings, and minimize cost, says Aaron Smith, a senior research specialist at Rensselaer Polytechnic Institute’s Lighting Research Center, Troy, N.Y., and a member of LRC’s DesignWorks team. “This often translates to new building solutions that affect many aspects of the design.” |
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McDougall offers a few key design pointers: “For an effective ambient/task lighting design, vertical and ceiling illumination is critical along with horizontal illumination. Brighter ceilings and walls enhance the perception of brightness even at lower light levels on the horizontal work plane.”
Selecting the proper lamp color temperature is another crucial choice. Essentially, when fluorescent sources with warm color temperature are used with very cool daylight, the lamps may appear yellow, notes DiLouie. According to McDougall. “If the space is typically occupied during daylight hours, a high color temperature of more than 4100K is recommended. If the space is occupied often during daylight hours and at night, a compromise in a lower color temperature should be considered.” DiLouie adds that diffuse sources such as fluorescents can be helpful to match the diffuse nature of daylight.
Overall, says McDougall, the electric lighting design should take into such factors as:
• lamp efficacy (lumens/watt)
• light output
• color rendering index
• lamp life
• lumen depreciation
• mercury content
• fixture efficiency
• luminaire photometry
• glare prevention
When it comes to controls specifications, McDougall says he often sees daylighting controls as leaving much to be desired. “We see many examples where lamps, ballasts, and fixtures are specified clearly, but the specification for the daylighting control is too general to know it will be compatible,” he explains. “This is a huge issue, as the general nature of the daylight control specification also leads to problems on what system should be approved during construction submittals and how it should be wired and then calibrated in the field.”
To address compatibility issues, designers should specify the following key variables:
• photosensor type
• location and measurement illuminance range
• number of ballasts that can be controlled
• calibration settings for when the light system should start dimming or stepping off
PASSIVE SOLAR—HIGH SUSTAINABILITY
To accompany technological advancements in lighting controls and more sophisticated daylighting designs, passive solar strategies for illuminating and heating a building can go far in achieving energy savings. “Passive solar lighting strategies are very important,” confirms Richard King, AIA, a senior associate with RMJM, Philadelphia. “Designs can often feature spaces that work for a better part of the day with the lights turned off. What could be more sustainable?”
Care should be taken to consider thermal and illuminance effects, says Wymelenberg: “The most important first step is to ensure there is enough mass to make use of solar gain. The second step is to be careful to introduce solar gain in a manner that does not cause glare.”
In addition to tying passive strategies to the local climate and building design, Building Teams must consider such feasibility factors as the number of heating degree days, sunlight availability, and surrounding window obstructions. “From the onset, passive solar heating needs to be an integral part of the building’s thermal equilibrium and direct the design of the fenestration and mechanical systems,” says lighting consultant Tanteri. “Following this are superior envelope design, building components, and a high standard of construction.”
According to McDougall, passive strategies that can be employed to help control direct sun and convert it into useful daylight include tubular skylights, light louvers, glazing with integrated louvers, fiber-optic systems, and simple devices like interior baffles. RMJM’s King particularly likes tubular lighting devices. “Some of the more interesting work being done in daylighting right now involves pushing light into spaces which otherwise could not receive it,” he says. “For example, light tube systems are like supersized fiber optics and are bringing life to spaces which would otherwise only be lit artificially.”
Other lighting technologies such as light-emitting diodes (LEDs), dynamic lighting, and high-dynamic-range imaging promise to raise standards for lighting and daylighting designs. “All of these technologies are in various stages of development and will no doubt improve the suite of tools designers have to incorporate comfortable daylighting that saves energy,” says Wymelenberg.
For example, dynamic lighting technology—introduced by Netherlands-based lamp manufacturer Philips Lighting—tackles the problem caused by dimming and shutting off electrical lights, which causes a perceptible shift in color temperature that can disturb building occupants. By putting differentially dimmable cool lamps and warm lamps within the same fixture housings, the resulting tandem allows for flexibility in combined color temperature and intensity, according to Wymelenberg.
Seeking to complement the natural cycles of the human body, the dynamic lighting approach consists of four states: 1) In the morning, a cool light helps raise the energy level of people coming into the office, 2) at midday, the light level decreases and a warm light encourages relaxation; 3) to counter the “post-lunch dip,” the light level rises to a cool white; and 4) at the workday’s end, an even cooler white light helps provide an energy boost for the journey home.
High-dynamic-range (HDR) imaging, a technology developed by Lawrence Berkeley National Laboratory, was first introduced on a large commercial scale in the New York Times Building in midtown Manhattan. Illumination sensors were installed on the building perimeter facing the glass to the exterior. Spatial luminance data from pixels captured by a digital camera was then calibrated with data collected by the sensors in order to develop a blind control system to optimally minimize glare, according to Wymelenberg.
LEDs are also being used more commonly in general illumination applications. Though the results tend to be good, a new U.S. Department of Energy initiative is addressing persistent issues of confusing or false information from lamp and fixture manufacturers. The Solid-State Lighting Quality Advocates program (www1.eere.energy.gov/buildings/ssl/advocates.html) is creating a verifiable product performance data label to list lumens, efficacy, watts, correlated color temperature, and color rendering index. This information will be posted on a label similar to the Nutrition Facts label printed on food product packaging.
PLUGGING AWAY
Because lighting, daylighting, and controls require a complex integration of expertise from many disciplines, there is still quite a learning curve ahead. And while there are a number of promising technology developments in the works, when it comes to integrating daylight with electrical systems, “Unfortunately, there are no silver bullets yet,” says McDougall. “Better education and experience within the design, construction, and facility management realm will be needed to keep pace with the improvements in daylight technology and to relearn the daylight expertise within the architectural community before Thomas Edison made his invention.”
About the authors
C.C. Sullivan is a communications consultant and author specializing in architecture and construction. Barbara Horwitz-Bennett is a writer and contributor to construction industry publications.
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