When it comes to constructing large areas of transparent building envelope quickly and cheaply, curtainwall is, and may always be, the reigning champion. In this age of mass customization, the ubiquitous enclosure system need not be dull. Manufacturers can rapidly produce extrusions and spandrel and glazing materials that will yield nearly anything architects want, from the sensuous stainless steel vertical lines of 8 Spruce Street (formerly Beekman Tower) by Frank Gehry, FAIA, to the horizontal ceramic rods that march up the sides of the New York Times building by Renzo Piano, Hon. FAIA.

However, there aren’t many architects out there working with Gehry- or Piano-size budgets. The challenge for the have-nots is finding ways of designing buildings that will stand out from the hundreds of millions of square feet of innocuous curtainwall erected all over the globe over the past half-century.

Since structural silicon eliminated projecting mullion caps, the greatest innovations have been in what the extrusion will be glazed with—not what kind of extrusion will be used. Shopping around for a fabricator and prudently selecting glass and spandrel materials often opens up intriguing design possibilities that can be achieved at a very slight cost premium.

Façade as Graphic Design

BFC Partners, the owner-builder of Toren, a residential tower in Brooklyn, N.Y., began meeting with Skidmore, Owings & Merrill (SOM) five years ago with a difficult problem: the need to differentiate its project from the grid-paper-faced condos that seemed to be sprouting up every other week in New York City.

“There were definitely graphic intentions here,” says Kristopher Takacs, AIA, who was the project manager for SOM. The firm approached the design of the façades as they would the graphic design of a wrapper for a package, he says. Taking vertical bands of material, and slicing and jogging them left and right, was intended to distract the observer’s eyes from the column lines. “Usually, verticality is something you celebrate in a tower. In this case, we did not want to make it a heroically tall building. Thirty-seven stories in Brooklyn is already pretty tall,” Takacs says.

Clear vision glass is pushed toward the vertical edges of the building, while darker glass is restricted to the center of each façade. The columns of the steel-framed building were pulled away from the corners as well. This lightens up the appearance of the structure and opens up the corner views looking from the inside of the building out. Google Earth was used to verify the nature and quality of the views from each part of the façade.

Large-scale unitized curtainwall construction is not unusual for New York City residential high-rises, and is normally favored because the repetitive manufacture of hundreds of units makes it extremely economical. Unfortunately, the very definition of repetition means that almost every residential tower in the city looks exactly like the next.

At Toren, which means “tower” in Dutch, the opposite approach was needed. While the budget for the project was very conservative, with some effort, the design team was able to locate a manufacturer in Argentina that could execute a complex design without a cost premium. It translated SOM’s elevations into eight vision and spandrel panel types, ranging between 2 to 6 feet in width. These, in turn, were configured into some 200 unitized, pressure-equalized glass-and-aluminum panel units, most of them 10 feet tall to span from floor to floor.

The aluminum panels come in two types, both bright silver. Some are flat, and the others are embossed with 3-inch- or 5-inch-diameter dimples. The structural-glazed glass panels contain spandrel or vision glass; the operable windows (awnings) always have vision glass. Clear and dark glass were used for both the vision and spandrel panels. The lighter-glass spandrel, which is paired with the clear vision glass, has gray frit applied to it; the dark spandrel paired with the darker vision glass has a layer of black frit.

During installation, many different combinations of a few basic units were installed in nearly every floor. It was the unique order in which they were installed that allowed Toren’s unusual façades to emerge. Even the building’s crenellated podium is a variant of the curtainwall system.

The design team had first considered window-wall systems (typically the first choice of residential developers, because of their low cost and ease of installation), but found their ubiquitous appearance limiting to creativity. “We did a lot of ‘optioneering’ and what we came up with was curtainwall,” Takacs says. That decision was informed by the expertise of curtainwall design specialists Israel Berger & Associates. The key, however, was finding the Argentinian manufacturer. “That allowed us to take advantage of the global economy for construction materials,” Takacs says. “The quality of their product is excellent. And the owner-builder was able to stay within their budget throughout the whole construction process.” The envelope materials budget was approximately $50 per square foot.

SOM designers went to Uruguay and Argentina for a series of meetings to study product quality before selection. These meetings included mock-ups and full-scale testing. For its part, the manufacturer had an employee on site full-time during construction. The project, which was completed last year and whose apartments have sold very well despite the recession, is on target to receive LEED Gold.