Posts tagged with "daylighting":
Wood siding and high performance glazing invite nature into the workplace.For their new headquarters in Wilmington, North Carolina, Live Oak Bank's leadership sought a design that reflected the institution's unique culture, particularly its focus on cultivating meaningful relationships with both customers and employees. "Their employees work hard," reflected LS3P's Laura Miller, whose firm was selected to design the building after a small local competition. "The folks who run Live Oak Bank want to recognize that." At the same time, she said, "they wanted it to be somewhat unassuming as well. They want to just quietly go about their business, and be the best at what they do." The architects' solution, a two-story U-shaped structure clad in local cypress and high performance glass, gives equal measure to both concerns. Plentiful glazing maximizes daylighting and views for occupants, while the long wood facades are designed to reflect attention back to the natural environment, further integrating the building into the site as the material weathers. The headquarters building's previously undeveloped site was a perfect fit for the project brief. Located in the heart of the city, the parcel is nonetheless adjacent to a nature preserve. "It's a little island of tranquility in the middle of Wilmington," said Miller. "It's convenient, but once you enter it, you feel like you're in a secluded, calm environment." Unlike the traditional office block, LS3P arranged the interior program in a U shape around a central courtyard. "It's not the most efficient in terms of square footage, but the bank wanted every single employee to have beautiful views either to the lake or to the grove of live oak trees," explained Miller. Courtyard terraces, decks, and a full-length second-floor balcony can be used as workspaces on nice days, and further encourage a dialogue between indoors and out. In light of Live Oak Bank's desire for a building that blends into the natural environment, the architects gravitated toward wood siding. "We looked at quite a few images with different types of wood," said Miller. "Cedar is often used for building exteriors, but it's not something you find naturally here in eastern North Carolina." Instead, LS3P chose cypress, a local product that ages gracefully. Because they had a contractor on board right away, the architects were able to construct a series of mockup walls on the site even before it was cleared, demonstrating the appearance of the siding at installation, after one year, and after ten years. Per the client's wishes, LS3P designed the bank headquarters to provide every employee with daylighting and views. But the large amount of glazing that resulted presented a potential problem with thermal gain, especially on the south-facing facade. The architects selected a high performance glass, further protecting against glare and solar gain with fixed sunshades. Tested through a series of sun studies in Revit, the airfoil-shaped shades are integrated directly into the curtain wall system. Interior motorized blinds provide an additional layer of environmental control. On the stair towers and at the main entry, the architects offset the wood siding with grey metal panels. "The company is growing so quickly that we were constantly adjusting the design to accommodate more people," said Miller, noted that the project's square footage more than doubled between concept and construction. "The two legs of the U got pretty long. We wanted to break up the long horizontal facade, but we didn't want it to be jarring." Instead, the metal panels match the curtain wall framing and stucco base, maintaining the project's neutral palette. Live Oak Bank's new home does not look like the headquarters of a national bank. Rather, it looks like a comfortable place to work and visit, a place where ego takes a backseat to service. Fortunately, that is exactly what the project's clients—and its architects—wanted. "It's not a typical bank where people just drive through and get their cash," said Miller. "Their bank is really more about customer service and employee satisfaction."
Building technology research center features wood, integrated photovoltaics, and green wall.When John Robinson began formulating a vision for the University of British Columbia's (UBC) Centre for Interactive Research on Sustainability (CIRS), he did not start small. Robinson, who is responsible for integrating academic and operational sustainability at the university's Vancouver campus, dreamed of constructing the most sustainable building in North America, a monument to and testing ground for energy-generating strategies. Invited to join the project in 2001, architects Perkins+Will sought an approach combining passive design and innovative technology. Featuring a facade of locally manufactured wood panels, high performance glazing, solar shading with integrated photovoltaics, and a green wall sunscreen, CIRS is a living laboratory for the research and practice of sustainable design. The initial concept for the building included 22 goals centered on three themes, explained Perkins+Will's Jana Foit. First, CIRS was to have a net positive environmental impact. In addition, the structure was designed to provide an adaptive, healthy, and socially generative workplace for researchers, staff, and students. Third, CIRS would utilize smart building technologies for real-time user feedback and testing. The building envelope was a critical component of the project's overall environmental strategy on both conceptual and practical levels. "The overarching design idea is to communicate sustainability, to make it visible and apparent," said Foit. In terms of pragmatics, the architects focused on reducing heat gain and providing 100 percent daylighting to the interiors. To reduce solar gain, Perkins+Will reduced the window area from the current code of 40 percent maximum to 31 percent. They installed fixed and operable triple-glazed windows on the ground floor, and fixed and operable double-glazed windows above. For cladding, the architects selected Multiple Ply Cedar Panels from locally-developed Silva Panel—one of the first solid wood products designed for rain screen application. "The exterior panels were detailed and designed to be removable, to allow for material testing and research," said Foit. CIRS' two-pronged solar shading program includes a network of fixed shades with integrated photovoltaics and a green wall. The former results in 24,427 kilowatt-hours per year in energy savings. The architects designed the green wall, meanwhile, to protect the west-facing atrium, which lacks a mechanical heating or cooling system. Together with a combination of solid spandrel and vision glass, the living screen achieves 50 percent shade during the warmer months. "The plants are chocolate vines, which lose their leaves in winter, allowing passive heat gain into the building," explained Foit. "In the summer, when the vines are in full bloom, the leaves provide shading for the atrium." In an important sense, the CIRS story did not conclude once construction was complete in 2011. Rather, the proof of CIRS' value as a demonstration tool is in its ongoing operations. The building returns an impressive 600 megawatt-hours of surplus energy to the UBC campus each year—and continues to rack up sustainability prizes, including the Royal Architecture Institute of Canada's 2015 Green Building Award. But perhaps more importantly, thanks to publicly available performance data and a "lessons learned" document compiled by UBC, CIRS has fulfilled Robinson's dream of promoting green design through the construction of a transparent, replicable model.
A geometric corrugated metal and glass facade integrates industry and nature.Barkow Leibinger's original scheme for HAWE-Werk Kaufbeuren, developed for a competition several years ago, was "a completely crazy origami thing," recalled partner Frank Barkow. But upon winning the commission and learning that the factory's owners wished to build it in a single phase, "we had to be careful not to kill them with the budget," he said. "We really dumbed it down." The architects did, however, hold on to their original pinwheel plan, with production wings rotating around a communal courtyard. Inspired by Le Corbusier's "green factory"—a humanizing alternative to the "black factories" of the nineteenth century, which prioritized the flow of goods over the experience of the workers—Barkow Leibinger's design opens the HAWE plant to the Bavarian countryside with a geometric facade of corrugated metal and glass. In addition to drawing upon Le Corbusier's "green factory" concept, Barkow Leibinger also looked at industrial designs out of northern Italy in the 1960s and 70s, which in turn led them to experiment with a prefabricated concrete frame. "Usually we do steel," explained Barkow, "but in this case the client liked the precast concrete. It's a dirty industry—there's a lot of milling going on." The factory's exposed mechanical systems are integrated directly into the structure, passing through perforations in the horizontal beams. "It's not a very finicky factory," said Barkow. "We just put it where they needed it." Steel-framed shed roofs sit atop the concrete. Skylights look to the north, while the roof's south slopes are designed to accommodate photovoltaic panels. "The north-facing shed is a classical industrial solution," noted Barkow. "It brings in a lot of light, and saves a lot on artificial lighting." The arrangement of solids and voids on the facade emphasizes the resulting sawtooth profile. The architects carved the envelope into a repeating pattern of triangles and trapezoids, clad in glass and corrugated sheet metal, respectively. Most of the building's glazed surface is translucent white channel glass, with vision glass in the sliver of space closest to the ground. At the end of each wing, a broad horizontal window features a larger central section of channel glass framed by floor-to-ceiling panels of transparent glass to either side. "This is a kind of Corbusian idea: large end facades that look into the countryside," said Barkow. The factory wings are designed to be expansible, the end facade deconstructed and then rebuilt after the installation of additional bays. Barkow Leibinger gave HAWE-Werk Kaufbeuren's extra-production facilities distinct treatments. The lobby and office area is "a more blocky structure," said Barkow, with a transparent curtain wall. The cafeteria, too, plays up the connection to the courtyard with plentiful glazing. The architects designed the "edge spaces'" facades to contrast—but not clash with—the factory floor, explained Barkow. "They're adjacent spaces, but quieter and cleaner." HAWE-Werk Kaufbeuren earned a silver rating from the DGNB (German Sustainable Building Council) thanks in part to the architects' emphasis on daylighting and use of triple glazing, plus careful attention to the window-to-wall ratio. "Nothing spectacularly complex" was involved in the sustainability strategy, said Barkow. Indeed, the very simplicity of the design led to its success, practically and conceptually as well as in terms of environmental performance. From a complicated initial scheme to their final, streamlined, solution, Barkow Leibinger pared the plan and material palette to the bare essentials, with an eye to speeding construction while keeping the "green factory" ideal at the fore. "It's a large project in this landscape," said Barkow. "It's at a different scale, and more robust, than the factories we typically work on."
Terra cotta rain screen transforms brutalist eyesore into energy-efficient community space.Considered an aesthetic and functional failure almost since its construction in 1974, the old public library in Lawrence, Kansas, was overdue for a renovation four decades later. Gould Evans' challenge was to transform the low-slung brutalist behemoth, a poor environmental performer lacking both adequate daylighting and a sense of connection to the community, into an asset. "The desire was to try to come up with a building that basically reinvented the library for the community," said vice president Sean Zaudke. Rather than tacking an addition on to one end of the existing structure, the architects elected to wrap a 20,000-square-foot reading room and open stacks area around the old facade. In so doing, they altered the exterior for the better, swapping bare concrete for an earth-hued terra cotta rain screen punctuated by plentiful glazing. They also significantly enhanced the library's environmental performance, with early estimates suggesting that the new Lawrence Public Library will see a 50 percent reduction in energy usage despite a 50 percent increase in square footage. The decision to entirely enclose the old building within the addition was a critical component of the architects' sustainability strategy. "It allowed us to come up with a continuous facade utilizing a continuous insulation system," explained Zaudke. "It helped a lot with energy performance." Gould Evans chose a terra cotta rain screen from NBK to better tie the library to its surroundings. The building is located in an interstitial zone, immediately adjacent to buildings constructed in the 1950s but not far from Lawrence's thriving historic downtown. "We selected terra cotta because it could play by both sets of rules," said Zaudke. "It has an historic connotation, but it's also a much more modern-looking material." Daylighting was another of the architects' key concerns. "Because there were so few windows in the old library, wherever you went there was a sort of phototropic behavior," said Zaudke. "People just gathered around the windows. The rest was not as utilized." Gould Evans significantly altered the user experience by creating an open reading room within the wraparound addition, all of which is exposed to daylight. Other library functions are contained within the core, which in turn is lit both by a continuous clerestory and a series of Solatubes. The clerestory also prevents glare within the reading room by illuminating the inside of the facade. Gould Evans used prescriptive data to determine the overall balance of terra cotta to glass on the new facade—about 60/40—as well as on each exterior wall. To reduce thermal gain on the east and west faces, the architects placed terra cotta baguettes over each horizontal slit window. Together, the baguettes and the depth of the wall act as sunshades. As for Lawrence Public Library's old concrete facade, "we didn't want to just pretend it wasn't there," said Zaudke. Instead, Gould Evans partially overlaid it with a tongue-in-groove system of unstained wood. "The concrete had a harsh feel to it," explained Zaudke. "By wrapping it with wood and revealing it in places, there's this nice dialog that occurs. Everywhere it opens up is where some core function reveals itself—it's an interesting dynamic." At the library entrance, the architects brought the wood outside, encased in glass to protect it from the elements, said Zaudke. "That vocabulary of cracking open the library, of making it accessible, is present at the entry."
Earth-toned GFRC panels and contrasting metal wrap Petzl's new North American hub.When Petzl executives decided to move the climbing and caving equipment company's North American headquarters from Clearfield to West Valley City, Utah, they sought an opportunity not just to expand, but to design a facility that would reflect the brand's mission. "The two words we kept hearing from them were verticality and light," recalled ajc architects founding principal Jill A. Jones. "The types of products they design really have to deal with the vertical world." Working with a southwestern palette inspired by Petzl corporation founder and president Paul Petzl's recent visits to Mesa Verde National Park and Machu Picchu, the architects designed a combination administrative, training, and distribution center whose mesa-like bottom stories and punctuating tower appear as if carved out of desert rock. Given Paul Petzl's interest in the continent's arid landscapes, natural stone cladding would have seemed an obvious choice. But "to use stone would have been terribly expensive," said Jones—especially given the building's size, 80,000 gross square feet. "Getting a lot of stone in those larger panels would have been cost-prohibitive." Instead, the architects looked to GFRC, and worked with Tuscan Stoneworx's Dave Nicholson to develop a hybrid system of stone-backed GFRC panels. Rather than being hung on the building, the panels are adhered directly to it, thus avoiding any breaks in the thermal barrier. To perfect the look of the GFRC, the architects did no less than a dozen color studies before selecting three red-orange tones for application. The panels were sandblasted on site to render the color and texture more naturalistic. Nicholson helped ajc customize every aspect of the panel system, from color and texture to corner installation. "I don't know if he'll ever do that again," remarked Jones. The designers clad the tower and a bump-out over the front door in dark grey metal from Drexel Metals. "The tower itself was a sensitive area, because Petzl did something similar in their home headquarters in Crolles, France," said Jones. "It kind of felt dark and cold; we wanted to bring a lot of daylight into the space." The architects performed a series of daylighting studies, "to make sure we had daylighting opportunities in every occupied space." This led to the installation of high-performance glass on both sides of the office block to avoid glare. For the warehouse area, ajc chose tilt-up concrete. But as with the GFRC, achieving a natural look took some ingenuity. "We wanted not to paint the concrete, to get a more organic look," said Jones. "But staining the concrete was a challenge, because the form liners leave a natural coating on the panels." Contractor Sahara experimented with various solutions once the panels were in place to find a stain that the concrete would accept. Petzl's new North American headquarters is a fitting base camp for a company committed to pushing the limits of human exploration. Both inside and out—from its window-lit multi-story indoor climbing and training wall to its human-made, red-rock-inspired envelope—the building embodies a balance between reverence for the natural world, and celebration of the technology that makes that world a little more knowable.
Slate-clad addition to the American Swedish Institute evokes contemporary Scandinavian design.Minneapolis-based architecture, engineering, and planning firm HGA faced a tall order when the American Swedish Institute asked them to design an addition to the building known locally as "The Castle." The turreted Turnblad Mansion, constructed in Minneapolis' Phillips West neighborhood in 1908 and home of ASI since 1929, lacked the kinds of multi-purpose spaces required by ASI's cultural and educational programming—and was suffering wear and tear from a steady stream of visitors. "The project was about creating a front door that was more welcoming and inviting than the existing building, that can help protect the mansion and allow it to be used as a house museum," said project architect Andy Weyenberg. At the same time, "the mansion remained the focal point," he explained. "It will always be the identity of ASI. Everything we did, we wanted to respect the mansion and keep it as a centerpiece." HGA's intervention honors the primacy of the Turnblad Mansion while updating ASI's image with a contemporary facade inspired by Swedish building methods and materials. "The mansion doesn't relate well to the Swedish identity: it's a French Chateau," said Weyenberg. "ASI wanted to use the addition to reinforce their identity as a Swedish institution, but they were interested in doing that in a modern way, relating it more to modern Swedish design and architecture." Positioned across a courtyard, or gård (a traditional typology found in both rural and urban buildings), from the Turnblad Mansion, the new Nelson Cultural Center is clad primarily in slate shingles. "Slate is a common building material in Scandinavia, especially dark slate like that," explained Weyenberg, who says that it is primarily used as a roofing material, but that he has seen examples of slate cladding since working on ASI's expansion. The slate also matches that on the Turnblad Mansion's roof. "We're using material that's sympathetic to the mansion, but using it in a different way. It's clearly a new piece of architecture," said Weyenberg. He points out that although there's nothing particularly high-tech about how the cladding was installed—it is hung like a roof system—it promises environmental benefits in terms of durability and longevity. "The roof on the mansion has been in place 100 years," observed Weyenberg. The entrance to Nelson Cultural Center is lined with panes of blue textured glass, another nod to Swedish design. Sweden is known for its glassmaking, having produced art glass firms including Orrefors and Kosta Boda. ASI's collection also includes a number of significant glass pieces. "That was another way of tying the design back to Sweden, and creating a reference to the ASI's collection, while also creating a bold element at the entry," said Weyenberg. HGA worked with Louisville, Kentucky, glassmakers Architectural Glass Art (AGA) to combine layers of commercially available textured glass and resin to create the translucent panels. "There's not a strong reference in terms of its construction to Swedish glassmaking," said Weyenberg, "but there was a process in terms of working with AGA as a craftsman to come to a quality we all liked. We wanted something subtle in texture but with an organic quality that relates well to the slate." HGA took advantage of a consulting program sponsored by local energy provider Xcel Energy to locate windows and curtain walls to frame views of the mansion and maximize daylighting while minimizing energy loss. Other features contributing to Nelson Cultural Center's LEED Gold status include a vegetated roof over the gallery and event spaces. "Green roofs are a really common form of building in Sweden," said Weyenberg. "They've been building sod roofs on farm buildings forever." Nelson Cultural Center's contemporary design reflects ASI's commitment to celebrating the Swedish influence on the Twin Cities while connecting with Minneapolis' next generation of newcomers—including, in the Phillips West neighborhood, young Somali immigrants. "As part of this expansion, they were really trying to update their identity and keep themselves current," said Weyenberg. "Their core constituency is aging. They were looking for a way to keep themselves relevant, and to reach out to new audiences."
Net zero energy, LEED Platinum project raises the bar on eco-friendly office design.For its new headquarters in Los Altos, California, the David and Lucile Packard Foundation put its building budget where its mouth is. The philanthropic organization, whose four program areas include conservation and science, asked San Francisco-based EHDD to design a net zero energy, LEED Platinum building that would serve as a model of cutting-edge green building techniques. “They wanted to achieve net zero in a way that was replicable, and that showed the path forward for others to follow,” said project manager Brad Jacobson. “It was not just a one-off thing, not just a showcase.” The building’s facade was fundamental to its success as an example of sustainable design. “We were surprised at how significant the envelope is, even in the most benign climate,” said Jacobson. “Pushing the envelope to really high performance made significant energy and comfort impacts, and could be justified even on a first-cost basis.” EHDD began by considering the building’s siting. Because the street grid in Los Altos is angled 40 degrees to the south, orienting to the street would result in a long southwest elevation. The architects asked daylighting consultants Loisos + Ubbelohde what penalty this would entail. “They said you have to keep all solar gain out of the southwest facade; if you do that, the energy penalty will be in the realm of less than five percent,” recalled Jacobson. “But you really have to do an excellent job on sunshading. That was our mission.” EHDD designed deep overhangs over much of the facade’s southwest face, and added balconies and shade trees for additional protection. Where the glazing remained exposed, they installed external movable blinds from Nysan that operate on an astronomic time clock. “The blinds worked really well,” said Jacobson. “We were surprised how easy they were to commission and get working, and how relatively robust they are.” Thermal bridging was another area of concern for the architects. EHDD worked with Atelier Ten on thermal modeling of the wall, and discovered that any metal stud wall would sacrifice performance. They opted instead for wood stud construction, and switched to 24 on center framing to reduce thermal bridging through the framing structure. For insulation, the architects added one-inch external mineral wallboard from Roxul. On advice from structural engineers Tipping Mar, they installed FRP plates to separate external elements like balconies from the main structure. Because of the building’s location, EHDD did not initially consider triple glazing for the Packard Foundation offices. “We wrote it off at first,” said Jacobson. “We thought, that can’t be cost effective in this climate.” But Integral Group’s energy analysis convinced the design team otherwise. The improvement in comfort allowed by triple element windows from Serious Materials (now Alpen HPP) was such that the architects were able to eliminate a planned perimeter heating system, resulting in an estimated savings of twice the cost of the glazing upgrade. “It’s a really good envelope,” said Jacobson. “We did heat sensor testing of the building, and you can really see that it’s working as it’s supposed to. You don’t see the studs, and the windows are not leaking a lot of heat, so that’s been a real success.” The architects clad the building in local and sustainable materials, including FSC-certified western red cedar, stone sourced from within a 500-mile radius, and architectural copper. “Architectural copper is a really interesting material,” observed Jacobson. “It’s actually about 80-90 percent recycled because it’s valued. It doesn’t need refinishing and it patinas nicely. For a building being built to last 100 years, it has a good shot at never needing to be refinished or replaced.” Jacobson summarizes his firm’s approach to the design of the Packard Foundation headquarters as “Passive House light.” “At the same time we were doing a Passive House for a climate science researcher we’d worked with in the past,” he said. “We were working on both and learning from each. It’s a different type of building, but a lot of the same principles apply: good air sealing, eliminating thermal bridging, and pushing the envelope further than you think makes sense.”
Sustainability and high design meet in Leddy Maytum Stacy Architects' affordable housing complex.Designing a sustainable building on a budget is tricky enough. But for the Merritt Crossing senior housing complex in Oakland, California, non-profit developer Satellite Affordable Housing Associates upped the ante, asking Leddy Maytum Stacy Architects to follow not one but two green-building ratings systems. "They wanted to push the envelope of what they typically do and decided to pursue not only the LEED rating, but also the GreenPoint system," said principal Richard Stacy. "So we actually did both, which is kind of crazy." Wrapped in a colorful cement-composite rain screen system punctuated by high performance windows, Merritt Crossing achieved LEED for Homes Mid-Rise Pilot Program Platinum and earned 206 points on the Build-It-Green GreenPoint scale. The building was also the first Energy Star Rated multi-family residence in California, and was awarded 104 points by Bay-Friendly Landscaping. Merritt Crossing’s 70 apartments serve low-income seniors with incomes between 30 and 50 percent of the area median. More than half of the units are reserved for residents at risk of homelessness or living with HIV/AIDS. Stacy explains that in the context of affordable housing, sustainability means two things. The first is quality of life for the residents, "the sorts of things that have a direct benefit to the people living there," such as natural daylighting and indoor air quality. The second is energy efficiency. "Both non-profits and [their] residents have limited financial capabilities," said Stacy. "The one time they have funding for that kind of thing is when they’re building a building. So we focused a lot on the building envelope in terms of energy efficiency. At the same time, we wanted to have ample daylight and controlled ventilation.” Finding themselves with unused contingency funds during construction Leddy Maytum Stacy Architects upgraded the exterior skin to a rain screen system of SWISSPEARL cement composite. "We worked pretty closely with the SWISSPEARL company," said Stacy, who noted that Merritt Crossing may be the first building in the United States to use the system. Though the panels are installed like lap siding they offer "the benefits of a rain screen in terms of cooling and waterproofing issues," he explained. To accommodate the thicker skin, window manufacturer Torrance Aluminum designed custom trim pieces, which "had the added benefit of giving us the appearance of deeply recessed windows," said Stacy. Insulation was a special concern for the architects, both because Merritt Crossing was built using metal frame construction, and to minimize air infiltration in keeping with the green ratings systems. The building’s exterior walls are wrapped in 1-inch-thick high performance polyiso insulation from Dow Corning with a Grace Perm-A-Barrier VPS vapor permeable membrane. "As a result we ended up with a very, very tight building from an air insulation standpoint, which means you have to pay more attention to air ventilation," said Stacy. To compensate, Leddy Maytum Stacy Architects’ mechanical engineers designed a special air filtration system for the building’s roof, complete with built-in HEPA filters. The building’s southwest facade faces a freeway, presenting potential noise and privacy issues in addition to exposure to the western sun. "We did a highly layered facade on that [side] where the actual exterior wall is back three to four feet from another screen wall," said Stacy. The outer wall "is a combination of typical wall assembly as well as GreenScreen panels that form a webbing of open areas and solid areas that help with sunshading as well as acoustical [dampening] and privacy." Greenery in balcony planters will eventually grow up and over the screens. On the ground floor, the garage is also enclosed in GreenScreen trellising, to enhance pedestrians’ view without sacrificing ventilation. Leddy Maytum Stacy Architects’ Merritt Crossing proves that affordable housing does not have to look institutional. The facade’s vibrant colors—green on the northeast elevation, red on the southwest—and playful punched texture pay homage to the neighborhood’s patchwork of architectural styles and building uses. The first major building in the planned redevelopment of the area around the Lake Merritt BART regional transit station, Merritt Crossing sets the bar high for future developments.
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An in-progress look at the new transit hub's massive skylightAfter funding cuts and subsequent delays since construction started in 2005, the much-anticipated Fulton Street Transit Center is finally taking shape in Lower Manhattan. The $1.4 billion project will connect eleven subway lines with the PATH train, the World Trade Center, and ferries at the World Financial Center. In collaboration with artist James Carpenter, Grimshaw Architects designed the project’s hallmark—a 60-foot-tall glass oculus that will deliver daylight to the center’s concourse level. The hyperbolic parabaloid cable net skylight supports an inner skin of filigree metal panels that reflect light to the spaces below. AN took a look at the design’s progress with Radius Track, the curved and cold-formed steel framing experts who recently completed installation of the project’s custom steel panels: Metal framing was an ideal choice for the skylight’s large structure, whose 90-foot diameter required a high strength-to-weight ratio that couldn’t have been achieved with a heavier material like concrete. Cold-formed steel (CFS) could also be manipulated into the complex shapes necessary to achieve the skylight’s irregular shape. Though the project was originally designed as a stick-built structure, the design would have required workers to complete the construction of the complicated, sloping oculus walls while working five stories above ground. Proximity to the water raised concerns about severe storms that would have further compromised working conditions. The oculus also had to meet security standards surrounding the World Trade Center memorial sites, so the design team abandoned the stick-built approach and began to consult with Radius Track on an alternative construction method. The structure’s total surface area is approximately 8,294 square feet, comprised of 44 panels arranged in two tiers. Panel width is a constant 8 feet, while length ranges from 19 to 33 ½ feet excluding two smaller end panels measuring 4 feet by 14 feet. The knife-edge element at the top of the parapet is 167 feet long, with a profile that changes continuously along the diameter. Using BIM, Radius Track customized designs for the seven-layer panels that complete the walls of the oculus. The modeling software allowed the team to detect potential clashes within the panels and with other design elements early on, and also facilitated the rapid, offsite fabrication necessary for the project’s tight timeline. The custom panels are designed not only for performance but also for geometric precision. The seven layers include framing (studs, track, blocking, and knife-edge panels where applicable), steel decking, DensGlass sheathing (a drywall material used in exterior applications), waterproof membrane, drainage mat, insulation and curved metal girts to which exterior cladding is attached, and Tyvek wrap. While the materials used in the project are traditional, the methods to connect the layers are not. Each layer has its own particular pattern, making attachment details between the layers critical. (For example, the CFS layer is a grid, the decking consists of linear ridges aligned with one panel edge, and metal girts span across the panel.) Each layer required its own design and subsequent coordination to ensure the finished installation was as precise as possible. Several types of metal are used to create the oculus. The walls’ structural framing is 14 gauge (68-mil) cold-formed steel, a “beefier” design than Radius Track would typically employ because of high wind speeds and enhanced safety and security requirements that are now standard for government structures in New York City. Designers used 16-gauge CFS for the track that is wrapped horizontally around the oculus walls. Decking is VulCraft 3-inch steel decking and horizontal metal girts secure the insulation layers. At the parapet, Radius Track designed customized 16-gauge, laser-cut steel sheets to form the ever-changing slope that circles around the top of the structure. Some sections are opening to the public ahead of the anticipated mid-2014 completion, and the complex is eventually expected to serve 300,000 passengers each day with 26,000 square feet of new space that will also include new retail stores and restaurants.