Bent glass: Undulating and insulating

Hidden pocket parks in Manhattan invite pedestrians to escape the discordance of bumper-to-bumper traffic, blaring horns and screaming subway trains by enveloping them in the white noise of man-made waterfalls. Winka Dubbeldam, a designer and principal in charge at Archi-tectonics in New York City, created a visual counterpart to the pocket parks at 497 Greenwich St. The building’s custom-made façade echoes the hypnotic power of a waterfall with a breathtaking 11-story wall of cascading glass. For the residents of the multifamily building, it must be a bit like living under a waterfall.

“I wanted to do something that was architecturally unusual and that would distinguish itself from all other buildings in New York,” says Jonathon Carroll, whose company Take One LLC owns and developed the property.

He succeeded. Cricursa, a glass fabricator in Barcelona, took on the challenge. The fabricators manufactured the 43 panels of insulating laminated glass, each a high-technology work of art. It was as if Cricursa had to fulfill 43 different orders, manufacturing each unit sequentially, says Ferran Figuerola, marketing manager of Cricursa. “It made the project quite challenging.”

The 77,000-square-foot facility houses 25 lofts, an art gallery and retail space on the ground floor as well as a gym and a meeting room for tenants. As the curtain wall gains height, it folds over and embraces a six-story warehouse next door, creating an architectural détente between new and old urban designs.

“I liked the idea of maintaining something that has been there for 100 years,” Carroll says. He dislikes new construction that tries to masquerade as old. The brick warehouse reflected the fabric and technology of its time and he wanted to do the same with modern materials. “You don’t need to use brick, you can use all steel and glass,” he says.

Necessity proved to be the creative catalyst for the design. Built on the site of a single-story garage, building code allowed for a straight rise to 85 feet before requiring a setback that had to sit within an inclined plane of 2.7 to 1.

“That plane was interesting to us,” Dubbeldam says. From the outset, she was determined to look at the building code as a challenge rather than a restriction and the setback requirement intrigued her. “I didn’t know it was a plane because usually setbacks are kind of square,” she observes, like the right angles on layered wedding cakes.

Dubbeldam wanted to do something conceptual with the plane and began considering a single curtain-wall system instead of the two that would be the byproduct of a traditional setback design. She says, “it was important that the façade move away from being a two-dimensional separating device to something that was a three-dimensional zone you could occupy.” To achieve depth, the waves in the glass move on the diagonal. If the bends had been kept parallel to the mullions, Dubbeldam asserts, the impact would have been “unexciting.”

The ripple challenge

A combination of strategies conspires to create an intricate design. Joseph C. H. Tizn, project manager for UAD Group of Brooklyn, N.Y., which designed and constructed the curtain wall and glass bulkhead, cites three elements:

•   Sloping glass bend lines, three on the fourth, fifth and sixth floors, and one on the ninth floor

•   Inclined horizontal extrusions at four different degrees, -8, 14.99, 23 and the typical 90

•   Slanting floor edges.

The ripple effect of the asymmetry creates a sense of movement even where none actually exists. For example, the small cantilevered balconies that mark the seam where the new structure meets the old warehouse appear to move in and out as they make their descent down the building’s front. Their projections remain constant while the façade undulates behind.

Dubbeldam draped the building in glass to capture the light, sunsets and views of the Hudson River in its western exposure. Noise was not a concern because, she says, with no through traffic, Greenwich Street is quiet. The views of the water turned this Netherlander’s mind to thoughts of the Mediterranean, framed by waterfront balconies where residents may enjoy the scenery. In addition to the small exterior balconies, she indulged her vision further with long spans of interior balconies.

Vision in blue-green

The glass windows and panels are composed of a quarter-inch blue-green glass, a half-inch air gap and one lite of laminated glass with two 1⁄4-inch layers. All the pieces, including those with a fold, have flat edges. The fold rises or sinks from a flat plane and then dissolves back into a level plane where the pane meets its top and bottom mullions.

“Maintaining a good flat edge was critical to the success of the project,” Figuerola says. The joints in the structural glazing demanded that the panels function as if they were flat glass. Achieving both elements in a single piece of glass is extremely tough, Figuerola says, especially with the fold traveling at a diagonal across the panel. With 3D computer-aided graphics, the Cricursa team determined what the shape of the glass had to be when it was flat in order for it to form a plumb rectangle after it was bent.

Workers manufactured individual molds for each unit. And then they had to calculate how to modify the placement of the glass in the mold to allow for the minute differences involved as the glass within each unit was layered.

Cricursa developed flexible spacers to accommodate the different shaped glass forms, and the custom-extruded aluminum mullions were made in Hong Kong to match the angles.

When bending glass, it is important to maintain optical quality. That’s easy with a simple bend, Figuerola says, but “when you have straight segments and a sharp irregular bend, this is very, very difficult.” The strength of the laminated glass is achieved in the bonding of the two pieces of glass. The third piece of glass was strengthened through tempering. However, because of the unusual fold in the glass, Cricursa’s engineers and technicians could not rely on traditional tempering methodologies that involve rapid cooling. Instead, they had to resort to chemical tempering.

Even its lamination process differs from that of many glass benders, Figuerola says. Producers often use a liquid resin to bond glass because if the pieces do not match perfectly, the liquid will compensate for the irregularity by filling the space. But Cricursa uses a polyvinyl butyral film. It demands high-precision production, but delivers better optics and durability, Figuerola says.

Code requires operable windows because the facility is residential. Here the designers selected top-hinged, out-swing windows to provide ventilation. When open, they contribute to the design, emphasizing the ripple movement across the façade.

“Conventional curtain-wall glass is adhered dir-ectly to both horizontal and vertical extrusions,” Tizn says. But in the Greenwich Street building, the structural properties of the insulating glazing units minimize the amount of structure, says Bill Logan, a curtain-wall consultant with Israel Berger & Associates in New York City.

Here, the narrowness of the glass panels, less than 3 feet in height, allows them to support and span the horizontal members and eliminate structural stays behind the glass butt joints.

The horizontal glazing is supported by steel jambs at either end and bolted to the vertical steel lattice. The grid’s narrow steel posts, spaced about 7 feet apart, create relatively unobstructed views and a great deal of transparency, Logan says.

The entire process demanded extreme precision. “There was only an eighth of an inch tolerance for the installation of the glass panels,” Tizn says. The result is an “incredibly smooth transition between adjacent pieces of glass.”  The effort to realize such elegant architecture, elevated everyone involved in the project to a higher level of design, Tizn says.

Sources

•   Winka Dubbeldam, Archi-tectonics, 200 Varick St., Suite 507 B, New York, N.Y. 10014,  212/226-0303, www.archi-tectonics.com

•   Ferran Figuerola, Cricursa, Coll de la Manya, 08400 Granollers, Barcelona, Spain, +34-93-840-4470, www.cricursa.com

•   Bill Logan, Israel Berger & Associates Inc., 232 Madison Ave., Suite 700, New York, N.Y. 10016, 212/689-5389, wlogan@ibany.com

•   Joseph Tizn, UAD Group, 267 Vanderwoort Ave., Brooklyn, N.Y. 11211, 718/599-0350, www.uadgroup.com

497 Greenwich St.

Owner: Take One LLC, New York City

Cost: $40 million

Architect: Archi-tectonics in New York City

General contractor: York Hunter Construction Services

Curtain-wall and glazing contractor: UAD Group of Brooklyn, N.Y.

Curtain-wall consultant: Israel Berger & Associates Inc., New York City

Engineer: Consulting Engineers P.C., New York City