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Sun, Sky Brightness, and Glow: Making the Most of Daylight

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Sun, Sky Brightness, and Glow: Making the Most of Daylight By C.C. Sullivan, Contributing Editor | DAYLIGHTING TECHNIQUES | SUN, SKY BRIGHTNESS, AND GLOW: MAKING THE MOST OF DAYLIGHT LEARNING OBJECTIVES After reading this article, you should be able to: + DISCUSS the bene ts and ideal kinds of daylighting illumination desired for such interiors as workplaces, libraries, and museums. + DESCRIBE the types of enclo- sure technologies and whole- building design approaches for maximizing bene cial JEFF GOLDBERG/ESTO, COURTESY CARRIER JOHNSON+CULTURE CARRIER COURTESY GOLDBERG/ESTO, JEFF daylighting. + LIST techniques for improving daylighting performance. + COMPARE the methods or materials commonly used in daylighting applications. The Tidewater Joint-Use Library, Virginia Beach, Va., has an angled “day- light harvester” that runs its length to maximize available sunlight. o some project teams, “daylighting” and material degradation caused by ultraviolet means using glass area to admit direct (UV) light. sunlight, period. Yet there are better Building occupants and owners want useful, approaches to illuminating building uniform light, not high-contrast or high-heat interiors. Often, the sun’s direct rays sources, according to surveys like the semi- are the last thing you need for effective nal study led by the University of Washington daylighting. Sunlight comes with high (https://tinyurl.com/zhpx7h3). That’s why solar heat gain—measured as solar controlled and redirected sunlight almost heat gain coeffi cient (SHGC) for various always provides the best approach, while direct types of glazing and translucent materials—and rays may be counted among the least desirable Tcan lead to glare, occupant thermal discomfort, techniques. Building surfaces and enclosures BDCuniversity.com | BUILDING DESIGN+CONSTRUCTION | 47 | DAYLIGHTING TECHNIQUES | that maximizes the smart use of daylight has a multitude of benefi ts. Energy savings and health ‘THE BEST APPROACH FOR DAYLIGHTING IS TO benefi ts are both achievable.” Natural light, with the full visible light spectrum, has been DELIVER GENTLE, EVEN ILLUMINATION THROUGH- shown to increase alertness and productivity, says Pew. Views to the outdoors also improve OUT A SPACE. THIS DIFFUSED, COMFORTABLE mood and possibly health. Seminal research by DAYLIGHT IS THE BEST FOR VISUAL NEEDS AND Roger Ulrich at Texas A&M University reported an 8.5% advantage in recovery for patients in FOR MINIMIZING ENERGY USE.’ rooms with windows. — LAYNG PEW, AIA, WXY ARCHITECTURE + URBAN DESIGN Daylight is essential to sustainable design ratings as well as health certifi cations, notably the WELL Building Standard. Light helps “mini- receiving direct sunlight need solar control mize disruption to the body’s circadian rhythm,” systems, including shading devices such as says the International Well Building Institute, overhangs and fi ns that may be opaque or which spells out requirements for window per- translucent, solid or louvered, according to formance and design, light output and lighting the Best Practices Manual published by the controls, and task-appropriate illumination lev- Collaborative for High Performance Schools. els to improve energy, mood, and productivity. Canopies, window fi lms, and insulated glazing The effectiveness of daylighting strategies units (IGUs) with internal louvers may also be should be evaluated on the basis of human required. Façades and areas facing north, on usefulness, energy effi ciency, and other factors, the other hand, need ways to maximize daylight says Christopher Alt, RA, Principal and Techni- To renovate a 1990 commercial building in harvest. cal Leader with architecture fi rm Studio Ma, Boston for Columbia “The best approach for daylighting is to Phoenix. Alt’s team uses daylight simulation in Property Trust, design deliver gentle, even illumination throughout a design-phase project modeling in order to as- fi rm Dyer Brown opened up the northwest-facing space. This diffused, comfortable daylight is the sess spatial illuminance qualities, visibility and lobby with a fl oor-to- best for visual needs and for minimizing energy glare, thermal considerations, and the protec- ceiling, point-supported use,” says Layng Pew, AIA, a Principal with WXY tion of building contents. “The 3D simulations glazing system and high- refl ectance, specular wall Architecture + Urban Design, New York. “Design and analyses are especially important in our fi nishes. many museum and cultural building projects, in- cluding some in desert climates, where artifact protection is of paramount concern,” says Alt. Underlying photometrics and daylight modeling are highly effective in the early design phases DARRIN HUNTER DARRIN to assess a range of project goals, including: n Uniform light distribution n Low glare n Reduction of energy costs n Overall cost effectiveness n Safety and security issues n Maintenance requirements Controlled daylighting is historically elemental to the design of museums, yet recently some cultural institutions have erred on the side of using more artifi cial illumination, including halo- gen and LED sources, and less natural light. SPECIAL CASES FOR DAYLIGHTING Experts in museum design from Cooper Rob- ertson encourage expanded use of controlled daylight for gallery spaces through careful analy- sis and the application of novel building tech- 48 | BUILDING DESIGN+CONSTRUCTION | March 2017 nologies that “preserve safe light levels and environmental conditions for the art,” says NIC LEHOUX, COURTESY COOPER ROBERTSON Scott Newman, FAIA, a Partner. “Daylighting reduces the need for artificial illumination, allows works to be shown in the full light spectrum for which they were conceived, and accentu- ates the three-dimensionality of sculpture,” he adds. Newman describes the design of the new Whitney Museum of American Art, in Manhattan. For its extensive use of solar illumination, Cooper Robertson and design architect Renzo Piano Build- ing Workshop used fritted glass edges, interior and institutional designs,” says Moss. “For the shades activated by photosensors, and insulat- renovation of the Yuma Heritage Library, we To daylight the new ing glass units with a polyvinyl butyral (PVB) added four double-height structures to serve as Whitney Museum of interlayer. The façade designs respond to the light monitors for the one-story Carnegie town American Art, Cooper Robertson used fritted building’s position or solar orientation. The de- library, a daylighting strategy that transformed glass edges, inte- sign also admits light to wash interior walls and the scale and quality of the user experience.” rior shades activated by illuminate display areas. Other products and assemblies used to admit photosensors, and IGUs with PVB interlayers to At the Florence (S.C.) County Museum, con- tempered, useful solar illumination for daylight- illuminate display areas. trolled natural light illuminates the second-floor ing include view windows, high sidelights with galleries through filtered clerestories and light light shelves, wall-wash toplighting, central and scoops, says Newman. patterned toplighting, linear toplighting, and Whether for museums or any other use, po- tubular skylights. sitioning of openings is critical to the effective- Skylights, roof windows, and other forms ness of daylighting, according to Gregg D. Ander, of toplighting are highly effective for internal FAIA, of Southern California Edison. “The higher light propagation, but they raise similar ques- the window head height, the deeper into the tions about undesirable hotspots, glare, and space the daylight can penetrate,” writes Ander interior wear, says Kevin Krumdieck, AIA, LEED in the Whole Building Design Guide. AP, Principal with Carrier Johnson + Culture. “To Openings “should ideally be composed of two prevent unwanted heating or over-illumination, discrete components: a daylight window and a we assess the skylight orientation (north is view window,” Ander writes. In a typical space, preferred), the roof slope, and the skylight size the daylight window’s sill should be 7½ feet and spacing to distribute the daylight well, while above the finished floor, with a high visible light controlling heat gain and glare,” says Krum- transmission (VLT) of 50–75%. The windows dieck. In some projects, the firm uses solar for occupant view should be located below the panels integrated with sunshade elements to daylight openings, with a lower VLT. mitigate heat from high-angle sun. For some building types, the view windows For office buildings and workplace interiors, often are beside the point. That’s one reason north light is a valuable asset, says Brent D. Zei- Studio Ma Principal Christiana Moss, AIA, often gler, AIA, IIDA, President and Director of Design advocates for clerestory windows and other with Dyer Brown Architects, Boston. “Sunlight fenestration concepts with high sill heights coming from the west, and the setting sun, can ideal for lighting museums and libraries. “For be tough on open workspaces. It can be hot, both qualitative and quantitative reasons, we with long shadows and too much glare on moni- keep going back to clerestory in our cultural tors,” he says. “Morning light from the southeast BDCuniversity.com | BUILDING DESIGN+CONSTRUCTION | 49 | DAYLIGHTING TECHNIQUES | can have a wonderful through lower-height window areas causing visual quality, and in glare, or areas closer to the ceiling plane that the winter months this create excessive brightness during the day. low-angled sunlight Another tool is called dynamic tinting, an appli- helps warm spaces.” cation of smart
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