News
05.19.2010
Skin Craft
The contemporary curtain wall is rightly celebrated for its pre-engineered, clip-on effortlessness, but that's not the whole story by any means. AN takes a close look at four building envelopes that step beyond the norm in search of excellence in expression and performance, from Pei Cobb Freed's cost-efficient glass wall system for a tower in Milan to the ingenious recladding of a Manhattan office tower without disrupting a day of work.
Each of the curves in Pei Cobb Freed's curtain wall for the Palazzo Lombardia in Milan is of an equal radius, allowing the design to use only two curtain wall module types.
Courtesy Pei Cobb Freed
 
the insulated glass modules run floor to floor, with an 11-inch aluminum spandrel.
 

aluminum vanes between the glass block sunlight.
 
COURTESY pei cobb freed
 

Palazzo Lombardia
Milan, Italy
Pei Cobb Freed & Partners


Double-skin curtain walls, sometimes referred to as climate walls, come in many shapes and sizes these days. What can be said about all of them is that they inevitably cost more to fabricate and install than your basic single-skin, insulated glass curtain wall. The payout may be recouped in time with cheaper energy bills through increased thermal performance, and there’s satisfaction in doing one’s part for the environment, but the initial cost is enough to put the system out of range for many projects seeking sustainability. This is especially true in the United States, where such measures are value-engineered out quicker than you can say Global Climate Change. But the Palazzo Lombardia, a municipal building currently under construction in Milan, proves these systems can be completed at a reasonable price. Pei Cobb Freed’s competition-winning design for this 1 million-square-foot, 225 million-Euro regional government headquarters provides a refined climate wall that matches manufacturing efficiency with energy efficiency.

The secret behind Pei Cobb Freed’s cost-cutting wall is its repetitive, modular design. In plan, the building fills out an awkward site with four snaking 7- to 9-foot-high slabs that meet in several places to define semi-elliptical public courtyards. At merely 46 feet wide, these office blocks allow ample daylight into the interior. The curves in the plan are all of equal radius. This allowed the architects to spec only two different curtain wall modules, one for the convex curves that are 6 feet wide and one for the concave curves that are 5 feet 10 inches wide. The module widths were also calibrated to match the structural bays, which boast 36-foot spans. There are seven modules per bay on the convex curves, and six modules per bay on the concave curves. At over 11 feet high, all of the exterior modules, which are insulated glass units, run floor to floor with an 11-inch aluminum spandrel unit. The interior layer is a laminated glass unit that runs from floor to ceiling. “The systems themselves are very flexible,” said José Bruguera, a partner at Pei Cobb Freed who directed the project team, working closely with lead designer Henry N. Cobb and technology partner Michael D. Flynn. “The interior was also meant to be flexible to meet the needs of each new government, as after every election there is some change.”

The 3-foot air space between the two layers of glass is wide enough to access for maintenance and cleaning purposes. It also houses a shading system of micro-perforated vertical aluminum vanes. Controlled by a building management system, the vanes rotate throughout the day to reflect direct sunlight. The perforations maintain a degree of transparency even when the shades are completely closed, allowing dappled light to flow into the interior and views to pass out. The cavity also acts as a return air duct. “In the competition, we didn’t have the slab continue all the way to the outer layer,” said Bruguera. “There was a grating for walking, so that air could travel up multiple floors. However, local fire code required separation in the cavity, so we brought the floor slab all the way through and designed the air return to be floor to floor.” This also permitted the exterior wall to be hung directly from the slab, another cost-saving opportunity that sidestepped the need to design a dedicated truss system for support.

A 550-foot-tall, 41-story tower sprouts at the intersection of two of Palazzo Lombardia’s sinuous office blocks. The double-wall system continues all the way to the top of this new distinctive element on the Milan skyline, except on the south face, where building-integrated photovoltaic panels were used. Pei Cobb Freed designed the tower’s concave east and west faces as a formal response to the nearby Pirelli Tower’s convex profile, but the project also bears a kinship to that modern masterpiece’s forward-thinking spirit. 

Aaron Seward


 


Maki and associates aimed for Tower 4, shown above from each elevation, to express a minimalist sense of serenity.
courtesy maki and associates

World Trade Center Tower 4
New York
Maki and Associates with R.A. Heintges & Associates


Designing the new towers now rising at the World Trade Center site was a daunting task. On the one hand, you have the relatively straightforward program of an office building with a retail component in the podium. On the other, the weight of a site that holds a powerful emotional charge in the national psyche. Fulfilling the former while honoring the latter creates a dichotomy of purpose prickly enough to befuddle the most sensitive of architectural talents. This is doubly true of Tower 4, which sits directly across Greenwich Street from the center’s memorial, Reflecting Absence. To respond to this conundrum, Maki and Associates set their sights on refining the building’s envelope to a point of ethereality, removing it from the appearance of any association with making and spending money. “We had a moral responsibility to the public to deliver a spiritual design,” said Gary Kamemoto, Maki’s director on the project. “We decided to use a very minimal vocabulary, to create something very abstract that would allow the tower to have a quiet presence of dignity and serenity.”

The architects did not stop at minimalism. “As we travel back and forth to New York, we are always struck by three towers on the skyline—the Empire State, the Chrysler, and Citicorp,” continued Kamemoto. “They have a sparkling metallic materiality that shines in the otherwise drab mass of buildings. They make us feel a certain optimism that we thought would be appropriate for the World Trade Center site.”


A mockup of the podium's laminated glass modules with steel mullions.
 
COURTESY maki and associates
 
 

Maki began by creating a very simple, sculptural form for the 65-story, 550,000-square-foot building—in plan, a parallelogram chiseled away at the top to form a trapezoidal crown with two cutout corners running the entire height. To achieve a Brancusi-like abstraction on the surface of this volume, the architects, along with facade consultant R. A. Heintges and Associates and wall manufacturer Benson, designed an extremely reflective curtain wall module with no spandrel. Structurally glazed, the assembly of 5-foot-wide by 13-foot-6-inch-high unitized panels creates an abstract grid that completely hides the building’s floor plates and confuses any reading of scale.

Pulling this off involved a few unusual details. For one, the team worked with Dow Corning to develop a coating for the glass that would deliver the right metallic sheen. At 40 percent reflectivity—an anomaly in this day of super-transparent glass envelopes—the insulated glass units deliver impressive energy performance by casting off heat loading from the sun. Secondly, the lack of spandrel required the use of a touch mullion, which is a horizontal mullion that extends between the floor plate and the back of the glass. Though it plays no structural role, it does satisfy local fire code, which demands that both the top and bottom of a slab reach the exterior wall. Finally, Leslie E. Robertson Associates’ structural design puts only four massive columns at the perimeter, leaving the corners cantilevered and a jaw-dropping 80-foot clear span across the face of the building. While this was good for opening up a lot of free wall space, it also created significant differential movement that the skin had to be able to absorb. The team responded with a 1.75-inch horizontal joint in the curtain wall that can open to as much as three inches.

At the building’s podium, which houses the office lobby and retail space, Maki switched to a different skin. While unearthly abstraction worked for the tower, at the ground he wanted something more tactile and architectonic. There, transparent laminated glass modules are supported by a stick-built system of 3-inch-by-12-inch solid steel mullions. The system is robust enough to meet the World Trade Center’s stringent blast requirements, but its Miesian detailing keeps it elegant and provides a satisfying foundation for the luminous tower. “It’s a simple move,” explained Kamemoto. “You use a different modulation from the tower and it makes the base look special, makes it stand out.” 

AS


 
 

the ribbon-glass facade is based on five spline curves and fabricated by brooklyn-based roxy lab. 
courtesy cetraruddy

Lincoln Square Synagogue
New York
CetraRuddy with Front


The five undulating ribbons of the soon-to-be constructed Lincoln Square Synagogue facade are inspired by the ancient scrolls of the Torah, but the historic form is being interpreted with the most advanced BIM and parametric modeling systems around. Principal John Cetra and project manager Theresa Genovese of CetraRuddy designed the 70-foot-square curtain wall in collaboration with facade consultant Front’s co-founder Marc Simmons. Beginning with hand-drawn curves, the design was translated into BIM to create five spline curves in multiples of 16.5 inches—the optimal panel width, taking into account ease of fabrication and the appearance of the curves. Though glass panels and joints are identical, each of the 250 aluminum frames contains a customized suite of extrusions and transoms, many of which are being fabricated using CATIA by Brooklyn-based Roxy Lab, a facade research and development facility and sister company of Front.

the system is optimized so that each glass panel is identical.
Courtesy cetraruddy

Simmons described the curtain wall glass fabrication as the one analog process in the project’s hyper-digital execution. The architects envisioned using a real fabric interlayer to evoke the Torah’s parchment scrolls, and after extensive testing chose a synthetic fabric called Trevira, hand-placed to create delicate striations. The wall’s external lite contains the fabric laminated between SGP interlayers, while the interior lite is laminated white ceramic fritted glass. Placing the frit on the innermost surface will diffuse light from a 12-inch linear LED component in the base and head of each unit, causing the facade to glow.

The extent of Front and Roxy Lab’s involvement with the project grew in part out of larger contractors’ lack of interest in a highly complex yet small-scale project. For Simmons, though, the synagogue is a pilot for larger endeavors, like the Barclays Center at Atlantic Yards: “Essentially, we are taking the Lincoln Square, design-to-fabrication model and scaling it up to deliver the building for Forest City Ratner.” 

Jennifer K. Gorsche
 


 

 
the reskinned facade will boost efficiency by a third.
 
COURTESY mdeas
 
 

330 Madison Avenue
New York
Moed de Armas & Shannon Architects with W&W Glass


Designed in 1962 by Kahn & Jacobs, 330 Madison has a great location and 742,000 square feet of space, but also a facade that is long past its prime and its life expectancy. The original operable single-glazed windows allow air and water into the building and hike its energy consumption, but when owner Vornado hired Moed de Armas & Shannon Architects (MdeAS) to reclad the building, the team discovered the facade had one thing going for it—enough strength to support a new skin. According to MdeAS principal Dan Shannon, new cladding for buildings that predate 1968 can only project 4 inches from the existing property line, so using 330 Madison’s original mullions allows a new facade to be attached to the building’s 15-story podium as well as to its set-back tower.

The work will change the building completely. With an articulated curtain wall at the base and sleeker panels over the tower, it will look as new as nearby 100 Park Avenue, for which MdeAS was a finalist in this year’s Zerofootprint re-cladding prize. Though the new windows at 330 Madison will be nearly 20 inches larger than the original 7-foot-high vision panels, the reflective insulating glass units will help the wall assembly be one-third more energy efficient. Behind the glass, aluminum shadow boxes will cover the dated brown brick piers. “This tired old lady comes out a brand new building,” said Shannon.

As much as the building will change from the outside, perhaps the design team’s best trick will be doing the work while offices are completely occupied. Once the new skin has been attached, workers will remove the old windows at night, pulling them inside and installing aluminum trim kits to finish the frames. When employees return in the morning, they’ll hardly know it’s the same building; at least, according to the plan. 

JKG