[May 03, 2013] Let the Sun Shine In [Environmental Design + Construction] Tweet (Environmental Design + Construction Via Acquire Media NewsEdge) ADVANCED GLAZINGS AND DAYLIGHTING SYSTEMS CAN HELP FORGE THE ROAD TO ZERO-ENERGY BUILDINGS AND SIGNIFICANT SAVINGS, BUT ONLY IF DAYLIGHTING DESIGNS CAN AVOID UNWANTED SOLAR HEAT GAIN AND GLARE. As comfortable and appealing as the most creatively crafted indoor environments are, no modern building is complete without natural outdoor light. Documented to increase occupant comfort, productivity, healing, test scores and retail sales, the popularity of daylighting designs has been augmented even further by sustainable design trends and environmental consciousness. In fact, Jon McHugh, P.E., LC, technical director of the energy consulting and research firm, Heschong Mahone Group, Gold River, Calif., has been quoted as saying that the U.S. could reduce its peak electrical demand by 24,000 megawatts (MW) by increasing daylighting in existing buildings. Putting this into perspective, these savings would be the equivalent of power generated by 24 1,000-MW nuclear power plants or 48 500-MW coal-fired power plants. At the same time, the execution of a successful daylighting design is a true science since optimizing natural light while controlling solar heat gain and glare is no simple undertaking. Key to this endeavor is the thought out utilization of advanced glazing technologies. A LOOK BACK To fully appreciate the daylighting capabilities which the building industry is currently benefiting from, a look back at glazing's humble beginnings reveals how the technology has evolved. Rewind about 40 years, which is when early low-emissivity (low-E) coatings were first introduced. Thanks to microscopically thin metal layers sprayed onto the glass surface, windows became capable of reflecting the unwanted infrared component of sunlight while allowing the desirable visible component to pass through. This worked to boost thermal insulating properties, thereby reducing the U-factor and heat gain and loss. The next advance came in the form of sputter coatings as manufacturers figured out a way to vacuum-deposit this layer during float glass production. "Sputter coating works at the molecular level to produce outstanding performance, and it offers significant advantages over pyrolytic coating," explains Chris Dolan, director of commercial glass marketing, Guardian Industries, Auburn Hills, Mich. Although the next sputter-related development came about several years later, post-temperable sputter coatings then enabled fabricators to apply the glazing, which effectively shortened lead times on projects, lowered replacement costs and drove a greater adoption of high-performance glass in the marketplace. Eventually, manufacturers also developed a large-area magnetron sputtering process, which has enabled the application of more complex coatings with greater uniformity and quality control to a larger area, according to Dr. Helen Sanders, vice president of technical business development, Sage Electrochromics, Faribault, Minn. Furthermore, by layering the metallic and dielectric layers in different sequences and applying assorted gasses such as argon, nitrogen and oxygen, glazing manufacturers were then able to produce a wide variety of coatings to meet different design and performance needs. Next up was the development of doubleand triple-silver coatings, which utilizes either two or three microscopically thin silver layers during the coating process, combined with additional metal layers. "While maintaining the same visible light transmittance (VLT) as a single coating, double silver has a lower solar heat gain coefficient (SHGC) than single silver low-E glass," explains Dolan. "In other words, it filters the sunshine as a cool lighting source to a larger extent and provides a solution to energy efficiency in design of high-transparency structures." Another benefit leveraged by doublepaned glass is the creation of an airfilled gap between the panes, which, as mentioned, can be filled with monatomic gases and vacuumed, thereby boosting the R-value. However, the gap size needs to be fine-tuned to ensure optimal performance. "If the gap is too thin, heat can easily conduct across it. And if the gap is too thick, convection currents arise that actually promote heat transfer," explains Scott Schuetter, P.E., LEED AP BD+C, senior energy engineer, Energy Center of Wisconsin, Madison, Wis. "An optimal thickness of about half an inch minimizes the heat transferred across the gap." Although triple-glazed units do come at a price tag, they currently offer the highest available light-to-solar-gain (LSG) ratio, amongst conventional glazing technologies, in that they block the most solar energy while letting in the most light. ADVANCED GLAZINGS In addition to sputter low-E coatings, double- and triple-paned glass, a number of other innovations-namely spectrally selective coatings, fourth surface coatings, dynamic glass, angularly selective optics and translucent panels-offer high levels of performance and flexibility for designers. Defined by the U.S. Department of Energy (DOE) as glass with an LSG of 1.25 or better, spectrally selective coatings selectively reflect long-wave infrared and solar near-infrared rays while transmitting a higher ratio of daylight. "Spectrally selective low-E coatings are available with one, two or three layers of silver," says Dolan. "Each layer improves the coating's selectivity and can be applied to clear or low-iron glass as well as various types of tinted glass, producing 'customized' glazing systems capable of either increasing or decreasing solar gains, according to the aesthetic and climatic effects desired." While low-E glazings were traditionally limited to the hermetically sealed surfaces on the glass, manufacturers have come up with ways to coat a third, and even fourth, surface on double-glazed units. For example, Guardian's SunGuard IS (interior surface) 20, can be applied to the #4 surface of a double pane or on the #6 surface of a triple-glazed unit. This, combined with a low-E coating on the second surface, delivers lower U-factors and better energy savings. As for skylights, perhaps the most significant advance has been the application of prismatic patterns to refract light for diffusion without heavy colorants to enable optimized VLT. "This maximizes the amount of hours per day that a device can provide properly diffused daylight as a main illumination source," explains Grant Grable, LEED AP, vice president, managing director, global business development, Acuity Brands, Sacramento. Similarly, today's tubular daylighting devices (TDD) "selectively harvest" daylight and deliver a more consistent light output thanks to finely tuned optical domes, tubes and diffusers. "In addition to advanced refractive optics, we have also pioneered spectrally selective optical tubing systems, thereby filtering those unwanted wavelengths out. As a result, the TDDs are capable of producing LSG ratios that are double that of traditional advanced glazing systems during problematic times of the day and/ or year," relates Neall Digert, Ph.D., MIES, vice president of product enterprise, Solatube International, Vista, Calif. Although not all designers specify translucent panel systems, they are quite popular in schools and public facilities. Traditionally known for controlling solar heat gain, newer advances in resins and fiberglass has helped to boost VLT levels. "We've also seen increased interest in systems that utilize multiple glazing materials such as translucent panel and glass combination skylights and operable glass window and translucent wall panel combinations," says Mark Mitchell, marketing manager, Major Industries, Wausau, Wis. While static glazing seems to have reached a ceiling with the highest performing products achieving an LSG of 2.3, electrochromic (EC) glass has shattered that barrier, and today's dynamic glazings are capable of LSGs greater than 6, with a solar heat gain as low as 0.09. "The technology uses a thin assembly of several layers of transparent electronic conductors sandwiched between two pieces of glass," explains Dolan. "Low voltage applied to the conductors moves the ions to the electrochromic layers which sparks the tint change. Reversing the voltage restores transparency to the window." EC glass also provides a nice solution to glare issues. For example, in a typical office setting, employees will lower the blinds to block out the glare during peak sunshine hours. However, more often than not, occupants neglect to open the shades again, thereby compromising the potential for natural light and views. On the contrary, EC glass dynamically tints during bright conditions and then returns to its clear state once the intense sunlight has subsided. "EC glass controls can also be integrated into dimmable lighting systems to provide a combined façade light management system that works seamlessly with the glazing to optimize both energy efficiency and occupant comfort," adds Helen Sanders. While the technology is certainly exciting, a relatively high price point is currently impeding a greater market penetration. Furthermore, the units are currently somewhat restricted in size, which is also limiting its application. DAYLIGHT WINDOW, VIEW WINDOW Beyond the latest technologies, optimized window placement and sizing is also an important component of daylighting design. However, even before reaching that point in the design, careful building orientation is absolutely essential. The key here is setting up the structure so that the longer axis runs east to west, thereby minimizing the east and west-facing façades, which are the most subject to intense sunlight and associated solar heat gain and glare. Ideally, the building should optimize its daylighting through the north and south elevations. While designers will often specify the same glazing for the entire building, this isn't necessarily the best strategy as the different façades usually have very different energy performance and daylighting requirements. Consequently, it may very well be worth the extra effort to optimize the glazing for each elevation to boost performance. In terms of the window design itself, designers recommend tall window head heights as this is the key to deep daylight penetration. "As a basic rule of thumb, windows provide adequate daylight for a distance of 1.5 to 2 times the height of the top of the windows," states Dane R. Sanders, P.E., LEED AP BD+C, principal, Clanton & Associates, Boulder, Colo. "So, windows with a 10-foot header height will provide good daylight for the area within 15 feet to 20 feet from the windows." Another common strategy is specifying two separate windows-a daylight window and view/vision window-inside one unit. "When properly designed, the daylighting fenestration allows interior contrast ratios to be balanced with vision glazing, thereby maximizing visual comfort for the space occupants and allowing for maximum enjoyment of any available views to the outside," says Digert. In terms of how to execute this, the view window, which is the fenestration's lower portion, should have a higher visible transmittance of greater than 50 percent, and in some cases, an exterior overhang for shading, according to Schuetter. Meanwhile, the glazing for the upper daylighting section glazing usually has a lower VLT and SHGC. Specifiers may also consider an interior light shelf to help limit glare. Case in point, at the University of Illinois Business Instructional Facility, Champaign, Ill., Pelli Clarke Pelli Architects and Clanton & Associates designed each classroom with four lower view windows, which topped offat six feet, and two long and narrow daylight windows above. "The 'classic' daylighting window arrangement worked very well with the brick and limestone façade with very classical proportions and a rhythm of repetitive window configurations," says Dane Sanders. "In this LEED Platinum building, the daylighting and lighting controls made a significant contribution toward the LEED credits for optimizing energy efficiency." Overall, another variable in the mix is the overall window size, as the more glazing there is,the more daylight and electric savings potential. "However, windows are poor insulators, meaning that the more windows a designer includes, the more heat is lost by conduction through them," cautions Schuetter. Consequently, a window-to-wall ratio (WWR) of 30 percent to 35 percent strikes a good balance between daylighting and building envelope performance. As a point of reference, ASHRAE 90.1-2010 allows a WWR of 40 percent and 5 percent for skylights as a percentage of the roof area. In the 2012 International Energy Conservation Code, only 30 percent of the wall can be fenestration with 3 percent for skylights. At the same time, it's important to note that these are prescriptive requirements and designers can opt to use a performancebased approach if they desire higher glazing levels, as long as the whole building energy consumption can be modeled at levels acceptable by the codes. Key to this discussion, however, is the fact that even the highest performance glazing unit cannot match up to the thermal attributes of a well-insulated wall or roof. Consequently, the use of glazing will compromise thermal performance. Of course, turning buildings into opaque boxes is not an option, but solely from an energy perspective, glazing's justification is the extent to which it can replace electrical lighting costs. Ultimately, "If you can minimize the percentage of the space needed to replace electric light with properly diffused daylight for the most hours per year, then you achieve the best total building energy perspective," says Grable. As for establishing glazing ratios and aperture size, Leora Radetsky, MS LC, lead research specialist, Lighting Research Center, Rensselaer Polytechnic Institute, Albany, N.Y., bases this decision on what's required to achieve target light levels for a range of design days. Radetsky is also a fan of light scoops, which use tilted, transparent, high-VLT glazing to bring in more light in the winter months and to better take advantage of natural light on overcast days. Overall, Radetky's team seeks to include the following principles in its daylighting designs: * Bring people to the light. Create daylight zones at the periphery of the building combined with an open office plan with low partitions. * Bring light in high. With horizontal windows placed higher, daylight can be brought in deeper and more uniformly than the same square footage of vertical windows. Skylight and light scoops may be included in this strategy. * Diffuse the sun. Prismatic skylights or interior baffles can prevent direct sunlight from reaching the workplane. For vertical glazing, simple, white horizontal blinds tilted up to 45 degrees can diffuse the light. * Use light color surfaces. Light-colored partitions, walls and ceiling further diffuse the light and increase the reflectance efficiency of the space. * Control the electric lights. One of the primary benefits of daylight is energy and demand savings, but unless the lights are dimmed or switched, daylight design on its own does not increase energy efficiency. Offering his own set of daylighting design guidance, Dolan shares the following: * Identify design intent including WWR, color and appearance, and building shape and orientation. * Examine performance versus look to determine the desired balance of transparency and reflectivity with solar heat gain. * Evaluate different coatings such as low-E, hybrid low-E or spectrally selective glass. * Take advantage of newer glazing trends including triple silver, EC or buildingintegrated photovoltaics. * Examine the glass from all the angles and in different conditions. TOPLIGHTING IN THE MIX As useful as windows are at bringing daylight into the interior, toplighting is even more of an effective strategy. Whereas perimeter daylighting systems can only penetrate about 30 feet inside, toplighting is a great way to pull light much deeper into the interior. Furthermore, a skylight is capable of letting in three times as much light per square foot as compared to vertical glazing, thanks to the roof's greater exposure to sunlight. "In addition, toplighting with skylights or roof monitors provides the most uniform daylight possible and the most potential energy savings from dimming or turning offthe lighting," says Dane Sanders. At the same time, skylights need to be carefully positioned and sized to avoid glare and to control heat gain. Specifiers should also be looking for glazing which maximizes VLT and offers a high level of diffusion to disperse the light most effectively and uniformly. In fact, some standards, including ASHRAE 90.1-2010, mandate 100 percent diffusion. However, balancing VLT and diffusion can be quite the juggling act. "For example, one can start with a clear glazing-which can have as much as 92 percent VLT as is found in clear acrylic skylights," explains Grable. "However, direct light will produce glare. The light needs to be diffused, and in order to do this, one needs to add colorants to create haze or diffusion to spread the light. But the greater the amount of colorant, the less VLT the glazing can produce." Ultimately, Grable sees the optimal daylight prescription as balanced illumination from multiple daylight sources. Another issue to consider is the fact that skylights will experience a seasonal variation with occasional intense brightness when the sun angles near the zenith, as opposed to dimmer rays of sunshine in the wintertime when the sun is nearer to the horizon. "In northern latitude locations, this variation can be evened out by tilting the skylight glazing toward the south," suggests Dane Sanders. Another form of toplighting that is gaining popularity, thanks to technological advances, are TDDs, which pipe daylight from the roof through a tubing system outfitted with sophisticated optics. "While seemingly simple in concept, today's advanced optical TDDs are exceedingly sophisticated, using a robust suite of selective refractive and reflective optical principles and technologies to provide controlled daylight to nearly any interior space in ways that was simply not possible just a few years ago," explains Digert. "Key 'intelligent' features include angularly selective passive optic daylight collection/harvesting designs, advanced spectrally selective reflective technologies, advanced optics for controlled and consistent placement of light on interior surfaces, and advanced under-controlled light output through the use of switchcontrolled optical dimming." Typically, TDDs are limited to the top two floors of the building, but some products claim to effectively transmit daylight through tubing of up to 50 feet or more. At the tube's end is a refractive lens, which runs between 14 and 24 inches in diameter, or is shaped as a 24-inch by 24-inch square to fit into a typical acoustic ceiling grid, according to Dane Sanders. Often, a diffusing panel or pendant is installed below the lens to evenly distribute the light. "Routing tubes through the ceiling plenum can be challenging since there are many other systems that are competing for space," he notes. "So, an integrated design effort is critical for allocating appropriate space in the plenum and in vertical chases to bring daylight down through multiple floors of the building. At the roof level, tube locations need to be coordinated with other building systems equipment to avoid shadowing and maintain good solar access." Another feature to look for is roof penetration flashing packages which are guaranteed not to leak, suggests Tate Walker, AIA, LEED AP BD+C, senior project manager, Energy Center of Wisconsin. In addition, specifiers should be aware that tubes can vary in quality, so it's important to make sure that the tube's interior coatings are capable of reflecting high levels of light to the interior. Although not as common, hybrid solar lighting is an interesting technology which uses lenses or parabolic mirrors integrated with solar tracking devices to transmit sunlight through tubes, or even fiber optics, where it is ultimately redistributed into a hybrid daylight/electrical system. One such system was developed by Oak Ridge National Laboratory where a parabolic mirrored dish tracks solar movement and focuses sunlight into fiber optics, and it channels the sunlight into 2-foot by 4-foot fluorescent luminaries. Commercially available through Sundolier, the harvested daylight is combined with LED lighting and can replace four or more skylights. "While the potential for these systems to bring daylight further into buildings is quite compelling, they are also quite expensive," notes Dane Sanders. BATTLING GLARE As designers tweak their daylighting designs in pursuit of that optimal balance between uniform light levels and solar heat gain, over-illuminated spaces or significant contrast levels can create the nemesis of effective daylighting-glare. "Shifting patterns of daylight, and in particular transitory patches of directbeam sunlight, should be avoided for any spaces where people have well-defined and non-moveable work stations and/or work environments," says Digert. Generally speaking, glare is often the hardest to deal with on the east and westfacing façades due to the sun's low angle during the morning and late afternoon hours. Consequently, exterior shading devices are a common strategy-vertical fins, in particular-to block as much direct sunlight as possible, according to Schuetter. While glare is easier to control on the south-facing windows, and even more on the northern façade, exterior overhangs are still strongly recommended. "However, neither vertical fins nor exterior overhangs are likely to mitigate glare entirely," cautions Schuetter. "Often, an interior blind is the only 100 percent guarantee of no glare. When utilized, interior blinds should allow some portion of diffused daylight into the space; 20 percent is a decent target." Of course, the main problem with interior blinds is the fact that more often than not, once a building occupant closes the blinds, chances are that they will remain closed, as noted earlier, thereby defeating the entire daylighting strategy. Consequently, "It is absolutely essential that there is a good plan for dynamic glare control, whether it be through blinds which are automatically retracted when the glare moves away to return the daylight harvesting and view, or automatically controlled dynamic glazing," states Helen Sanders. Along these lines, the Lighting Research Center has developed a Blind Minder device which monitors direct sunlight on the glazing and informs occupants when they can pull back the blinds. "Even a simple Outlook reminder that tells you when to pull your blinds up based on your window orientation can increase energy savings while allowing the occupant to have control over their space," suggests Radetsky. To a certain extent, fenestration sizing and glazing can also control glare. And while designers are often hesitant to reduce VLT any more than necessary, Dolan points out that even a VLT as low as 35 percent will still provide generous levels of natural light and not make the spaces feel dark or cavernous. To asses the potential for glare in a specific space, several metrics have been created to measure this, a number of which have been incorporated into daylight modeling programs. Essentially, this helps designers try out different fenestration and shading strategies to minimize glare issues. DAYLIGHTING AND NET-ZERO With a growing focus on net-zero building designs, to what extent does good daylighting potentially play into a zero-energy building (ZEB) design formula "You can't do a net-zero application without a whole-building energy model, which includes a comprehensive daylighting plan involving strategies for glazing, lighting, controls and blinds," responds Walker. In a similar vein, Dane Sanders explains, "The building façade represents a tremendous opportunity for improving the energy efficiency of buildings and indeed is where critical improvements are needed for enabling net zero." Putting things into perspective, Walker points out that electrical light can account for between 20 percent and 40 percent of a building's total energy use. Yet, overglazing can adversely affect heating and cooling equipment loads and sizing, which can also run between 20 percent and 40 percent of a building's power consumption. In fact, the EPA quantifies windows as consuming 30 percent of a building's heating and cooling energy, with a particular impact on peak demand and occupant comfort. In order to help enable buildings to reach zero energy, the DOE lays out the following three envelope strategies: * Low U-factor fenestration, such as triplepane glazing with highly insulating frames; * Dynamic solar control to capture heat when needed and block it when it's not desired, such as provided by dynamic glazing or automated exterior mechanical shading systems; * Integrated façades, which includes using good daylighting design to maximize the penetration of natural light combined with dimmable lighting controls to harvest natural daylight. Furthermore, "The future ZEB commercial window has dynamic solar control with an average U-Factor of 0.1 BTU/hr.oF. ft2, and is used as part of an integrated daylighting design, according to the DOE," says Helen Sanders. "In fact, the DOE estimates that if all windows in commercial windows in the U.S. were replaced today with highly insulating fenestration and integrated dynamic solar control and daylighting controls, $35 billion could be saved-and windows could be turned into energy suppliers of significant measure." In addition, the National Research Energy Laboratory projects that the energy savings from the wide-scale use of advanced windows could potentially reach nearly 6 percent of national energy consumption. While glazing alone will not contribute to site-based power generation required to achieve net zero, Digert stresses the importance of choosing fenestration technologies that work in concert with façade- integrated and rooftop photovoltaic systems. For example, TDDs can complement PV systems in that they minimize the space conflict on the roof between the need for space devoted to the PV system and the aperture area needed to effectively daylight interior spaces with a TDD. "Provided the selected TDD product's tubing or transfer system can achieve longer tube runs and bend around obstacles in the interior space, TDDs can be placed on the roof wherever space is available without compromising the interior daylighting diffuser and/or daylight fixture placement," says Digert. "Additionally, optical TDDs with appropriate turret design and/or options, allow for the optical domes to be raised higher on the roof plane to avoid shadowing caused by tilted PV arrays and maximize daylighting collection and harvesting." LOOKING AHEAD With building codes trending toward stricter energy requirements and the increasing cost of power production, it's anticipated that this will drive an even greater focus on the development of advanced glazing technologies. For example, in the works at Guardian is a new vacuum insulated glass technology which is two layers of glass fused together and separated by a very thin space of just 0.3 mm. The goal of the new system is to enable windows to reach thermal performance levels approaching those of an opaque wall. Ultimately, Guardian hopes to exceed insulation values of R-10, and R-11.5+ at the center of the glass, while still offering the daylighting benefits of transparent glass. Meanwhile, Schuetter is optimistic about photovoltaic technology which is incorporated into the insulating glass unit, advanced frits and etchings, "moth's eye" anti-reflective technology and suspended films such as heat mirrors. But beyond glazing units, Digert sees much potential in the realm of intelligent fenestration products. "These new complex fenestration technologies allow daylight to be delivered in a much more meaningful and consistent way to a building, allowing artful lighting design principles to be applied with daylight in ways that windows and skylights never do could before. Key examples include individually controllable layers of daylight, wall wash and decorative 'daylight chandeliers.'" At the same time, Digert wishes there was a way to shorten the time lag between the development of new technology and the needed supporting language that ultimately shows up in the building codes. Currently, this cycle takes approximately three years and is hindering the more widespread adoption of the latest technologies. "A new process needs to be developed that doesn't penalize or hinder technology innovation and adoption," he concludes.edc LEARNING OBJECTIVES After reading this article, you should be able to: * Differentiate between today's assorted glazing technologies and advanced daylighting systems, and how they work. * Recognize good design principles and viable technologies for toplighting. * Apply different design strategies to maximize daylighting while controlling solar heat gain and glare. * Appreciate how daylight modeling programs have developed, but recognize where their capabilities are still lacking. With a number of energysaving strategies including high-performance glazing, this new Bolingbrook, Ill. office and manufacturing facility for G&W Electric, supplier of power automation systems, is projected to save 2,944,317 kWh per year for an estimated annual cost savings of $237,000. IMAGE COURTESY OF EPSTEIN/ BALLOGG PHOTOGRAPHY Decorative Solatube fixtures accent the lobby with natural light at the company's headquarters in Vista, Calif.. IMAGE COURTESY OF SOLATUBE Electrochromic (EC) glass transitions between clear and tinted states based upon the application and reversal of a low-voltage electrical current. In a clear state, it permits natural daylighting and passive solar heating. Fully tinted, the EC glass offers a low solar heat gain of 0.09. IMAGE COURTESY OF GUARDIAN INDUSTRIES Daylight Modeling While daylighting modeling programs have certainly come a long way in their sophistication and technological capabilities, a discussion of today's software reveals more about what designers and manufacturers would hope to see in future iterations of these programs. For example, Leora Radetsky, MS LC, lead research specialist, Lighting Research Center, Rensselaer Polytechnic Institute, Albany, N.Y., is interested in photosensor and dimming ballast performance being incorporated into lighting software tools so that designers can better predict energy savings when lights are switched or dimmed. While some photosensor performance data is available through LRC's National Lighting Product Information Program, the actual power demand is a function of the interaction between the location and performance of the photosensor, the specific dimming ballast and the room characteristics, and there isn't much currently available data that shows the combined performance of the photosensor with different ballasts. Another shortcoming of daylight modeling programs is their lack of ability to conduct "apples-to-apples" comparisons of different products, particularly when products might reference different test standards or use different test methods. In addition, most software does not provide side-by-side comparisons of multiple design options, forcing lighting designers to individually generate and manually arrange rendered images in word processing, publishing or graphics software. "Workflow efficiency would be significantly improved if these side-by-side comparisons showing multiple design iterations could be saved, renderings automatically arranged and results graphically displayed by the daylight modeling software," states Dane R. Sanders, P.E., LEED AP BD+C, principal, Clanton & Associates, Boulder, Colo. As for the incorporation of newer daylighting technologies, there has been some progress in supporting the analysis of dynamic glazing and operable shades and blinds. However, more development is required to enhance the workflow and data management for modeling interior shade controls, dynamic or tunable glazing systems, tubular daylight devices and other daylight delivery systems. "Currently this analysis requires either tedious and time-consuming spreadsheet data management or customized software plug-ins to analyze and manage conditional logic and data from multiple modeling results," notes Sanders. While some manufacturers can provide light distribution files for each solar angle and sky condition, this data must be manually selected and changed for each time point. As such, Sanders would like to see daylight modeling programs that can automatically select the correct light distribution file for each time point and sky condition to help designers provide daylight autonomy calculations for the more innovative daylighting systems on the market. Fortunately, with conventional technologies, programs such as Daysim have begun including automatic calculation of annual and climate-based metrics such as daylight autonomy, continuous daylight autonomy, daylight availability and useful daylight illuminance. "These metrics give a much more comprehensive view of a design's year-round performance, as opposed to the best/worst/typical approach taken previously," explains Scott Schuetter, P.E., LEED AP BD+C, senior energy engineer, Energy Center of Wisconsin, Madison, Wis. Another popular program is AGi32 which offers sophisticated daylighting calculations and renderings. AGi32 accepts 3D models from other programs, making it an even more powerful tool. Demonstrating the separated view window and daylight window concept, Pelli Clarke Pelli Architects and Clanton & Associates designed four lower view windows and two long and narrow daylight windows running along the top of each classroom at the University of Illinois Business Instructional Facility, Champaign, Ill. IMAGE COURTESY OF PELLI CLARKE PELLI ARCHITECTS Optically designed diffusers in photometric distributions and aesthetics in the LightFlex daylighting system complement luminaires providing seamless transitions between sources. IMAGE COURTESY OF SUNOPTICS Translucent Systems In addition to products such as advanced low-E technology and dynamic glazing, another noteworthy daylighting strategy is translucent glass and fiberglass systems. Commonly used in schools and recreational facilities, one of the system's main benefits is mitigating glare and uncomfortable hot spots, as well as enhancing privacy. "Translucent glazing can be used to provide wonderful, diffused daylight to a space without the potential for problematic, transitory direct beams of light," confirms Neall Digert, Ph.D., MIES, vice president of product enterprise, Solatube International, Vista, Calif. At the same time, these systems must be carefully specified in order to accomplish this. "Careful and artful placement of translucent glazing systems, addressing occupant sightlines of these glazings and the adjacent architectural surfaces is required to minimize glare from these daylighting elements since they distribute daylight in all directions," he explains. "We have had great success with translucent systems in multipurpose rooms and gymnasiums," says Mitch Blake, principal of Jackson, Wyo.-based Ward+Blake Architects. "In addition to reducing glare and creating nicely diffused light, they are also tough enough to withstand the impacts of flying balls without failure or blemish." (c) 2013 BNP Media [ Back To TMCnet.com's Homepage ]