One World Trade Center Facade

20 Metals in Construction Spring 2015 One World Trade Center Facade 21 An icon before it was ever heavily reinforced structure. (The Dosso, a director at SOM. The built, the tower in Lower building’s structural design is design also maximizes the vision Manhattan is known detailed in a feature on page 26). area for building occupants and “Our most convincing attribute is facilitated the installation process throughout the world by that you look at the building and of the unitized curtain wall during a shimmering facade that it looks like an office building, and construction. Reinforced mullions, protects those within you have no idea how robust it some as heavy as 60 pounds even as it enhances the is,” says Kenneth Lewis, manag- each, are clipped at the edge of city around it. ing partner at Skidmore, Owings the slab and attach the curtain wall & Merrill (SOM). According to to the building. THE COMPLETION OF ONE WORLD Lewis, the architects at the New The glass itself is a single, Trade Center marks a milestone York office of SOM, led by chief low-iron insulated glazing unit in New York’s post-9/11 recovery. designer David Childs, wanted to (IGU). Its outer lite is thicker than The emblematic nature of the make the façade as uniform as what normally would be required building, located just north of the possible to create the image of for wind or hurricane force winds, massive pools set within the foot- a building that was aspirational a minimum of ⅜ inches when prints of the fallen Twin Towers it rather than defensive. standard thickness is ¼ inch. The is meant to replace, brought con- To achieve that seamless inner lite—laminated for the safe- tinual challenges to a design team look, SOM worked with Viracon ty of occupants—varies in thick- that briefly included World Trade to specify glass panels that were ness depending on location. The Center site master planner Daniel extremely large, building a special end result is a crisp, clear panel Libeskind. All that remains of his production line for that purpose. that produces pure reflection original concept for the building, While most glass panels at the rather than the oil-canning effect once referred to as the Freedom time of fabrication a few years ago that can create an impressionistic Tower, is the iconic 1,776-foot were configured to be about 10 appearance. “That makes the height, coinciding with the year feet tall with an additional spandrel form of the building read as a the Declaration of Independence piece, the glass panels at One whole instead of as an articulated was signed, and making One WTC are 13 feet, 4 inches and surface,” says Lewis. WTC the tallest building in the span the entire floor-to-floor height Though the shimmering glass Western Hemisphere, surpassing without intermediary mullions. façade stands as a kaleidoscopic The tower’s base as seen from the Chicago’s Willis Tower. “What we did that was unique with display of refracted light as the grounds of the National September 11 What emerged instead—after this project back then is that we sun and clouds move through Memorial and Museum, pictured in the a decade of endless dialogue, chose to run the glass fully by the the sky, the prismatic structure foreground. design, re-design, and construc- nevertheless is articulated with Facing The tower under construction slab edge so the horizontal mul- in 2011. tion—is a gleaming tower whose lion at the bottom doesn’t break stainless steel panels spanning

This page: Tex Jernigan; facing page and opening spread: James Ewing/OTTO Jernigan; facing page and opening spread: This page: Tex monolithic appearance masks a through the glass,” explains Nicole the full height of each floor at its

22 Metals in Construction Spring 2015 One World Trade Center Facade 23 “You look at the building and it looks like an office building, and you have no idea how robust it is.” Kenneth Lewis, Skidmore, Owings & Merrill

corners as the square plan at the exterior are a result of smaller bottom of the building shifts and curtain wall panels there. Rather tapers to a smaller square at the than the typical 5-foot-wide top. Measuring 200 feet by 200 panel, the glass stops short by feet at its base—the same size just over a foot, allowing intake as the footprints of the original and exhaust to occur through Twin Towers and the memorial those open slots. pools—One WTC is capped by A third major mechanical level a 150-foot by 150-foot square, is located in the podium. The po- which is rotated 45 degrees so dium wall base consists of vertical that the midpoints of the square laminated glass fins and hori- at the bottom are the corners zontal stainless steel slats. The of the square at the top. The more than 4,000 glass fins, each imposing shaft that gives form to measuring 13 feet, 4 inches by this transition—producing eight 2 feet, are positioned at varying isosceles triangles that run the angles in a regular pattern over length of the shaft and a series the height of the podium. This of octagonal floor plates at its pattern accommodates ventilation center—comprises over 70 floors for the mechanical levels behind of office space rising above the the podium wall. A reflective coat- 186-foot-tall concrete podium ing refracts and transmits light to at the base and culminating in create a dynamic glass surface three levels of observation decks in an attempt to assuage the spanning the 100th to 102nd floors. fortress-like appearance of the Above More than 4,000 laminated glass The 6-foot-tall steel band at its podium’s 28-inch-thick concrete fins and stainless steel slats form the roof has an upper elevation of walls. Glass over the lobby en- face of the podium, accommodating mechanical ventilation and breaking 1,368 feet and a lower one of trances feature a dichroic coating down the mass of the building’s base. ONE WORLD TRADE CENTER FACADE 1,362 feet—the two heights of that reflects and absorbs different the original Twin Towers. A series portions of the color spectrum, Location: 1 World Trade Center, New York, NY of communication platform rings resulting in a range of red, purple, Architect: Skidmore, Owings & Merrill LLP, New York, NY and a 441-foot-tall mast crown and green casts, depending on Developer: 1 World Trade Center LLC (a wholly owned corporation by the Port the observatory. the angle of vision. Authority of New York and New Jersey and the Durst Organization), New York, NY Just below and above the ob- Perhaps the greatest achieve- Structural Engineer: WSP Cantor Seinuk, New York, NY servation decks are mechanical ment of the curtain wall however, Mechanical Engineer: Jaros Baum & Bolles, New York, NY areas. In order to eliminate any is not what is visible from the Spire, Communications Rings, Cable Net Wall Engineer: Schlaich, Bergermann und louvers exposed on the exterior outside, but what is experienced Partner Gmbh, New York, NY wall, the designers created a ple- from the inside. The extra large, Protective Design Engineer: Weidlinger Associates, New York, NY num behind it, housing an interior unobstructed glass panels flood Construction Manager: Tishman Construction Corporation (An AECOM Company), walkway. Set back approximately the narrow floor areas around the New York, NY 5 feet from the curtain wall is a building’s core with daylight, cre- Curtain Wall Commissioning Consultant: Israel Berger and Associates, New York, NY continuous louver that conceals ating bright, sunny office space Structural Steel Erector: DCM Erectors Inc., New York, NY all mechanical distribution. The that requires very little artificial Architectural and Ornamental Metal Erector: Tower Installation, New York, NY empty vertical slots over these lighting. And of course, there’s Curtain Wall Fabricator and Erector: Benson Industries, Inc., New York, NY

areas that are visible from the always the view. James Ewing This spread: Metal Deck Erector: DCM Erectors Inc., New York, NY

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