7 WTC's reflective façade illuminates the city skyline*

James Carpenter's contributions to 7 World Trade Center (7 WTC) are both brilliant and muted -- it depends a lot on the weather.

Carpenter is the designer who, in collaboration with lead architect David Childs (of Skidmore Owings & Merrill), is responsible for the tower's inventive material and lighting scheme, including its 82-foot-tall stainless-steel base, interior "light block" design, and pedestrian-recognition lighting system around its sidewalks.

But among the considerable innovations, it is the tower's gleaming 750-foot-high façade that stands out most for the city to behold. The thousands of individual panels that comprise the façade are made of "water-clear" glass -- that is, glass low in iron that is purely transparent, without the green tint of most glass.

To capitalize on that transparency, the panels are not stacked end to end as on most buildings. Rather, for 7 WTC, Carpenter separated them using the three-foot linearly lapping spandrel between floors, on which finely corrugated individual steel panels are placed vertically next to a horizontal steel-blue strip that reflects light upwards.

Though Carpenter has yet to create a name for this design, the effect is a sort of shiplap (think roof shingles) that catches sunlight, moonlight, cloud patterns, and other atmospheric events and reflects them onto the building's glass. In essence, Carpenter says, the effect creates an "active skin."

Ultra-clear glass makes 7 WTC's skin appear transparent*

"We wanted a glass that transmits as much sunlight as possible without changing how the light is perceived inside -- and also to find a quality of light being embedded in the building," Carpenter says. "There are times when the building will reflect and blend in with the sky around it. Then there are other times…when the building can stand in complete contrast. Depending on the weather, the building may be dark while the sky behind it is light."

The high-performance glass coating lends to that effect, which in any given moment may appear different from near or far, even causing the tower to blend in with the sky behind it. The coating is practical as well, lending to 7 WTC's "green" standard by rejecting heat energy while retaining natural light.

Carpenter, a longtime Tribeca resident and regular collaborator with Childs, has been involved with the tower's design since the planning stages. His first challenge, long before the design team could arrive at the main-façade scheme, was addressing how best to accommodate the building's "podium" (its lower six stories), within which a major Con Edison substation operates.

The charge was to create a podium façade that allowed the necessary ventilation to the substation's four 80-megawatt transformers while answering the questions "How do you do something on the street that's physically and visually engaging? How do you take people who are making this passage every day and make their movement produce different qualities in terms of the urban experience of light?," says Carpenter.

The "linear lap" façade design is unique to 7 WTC*

Looking at the podium, the eyes see the outer-layer screen by day and the inner, LED-lit layer by night. "Your eyes only perceive the brightest optical values," Carpenter says.

To visually link the podium with the "crystal" tower above it, Carpenter and the design team created a sort of box of light that he calls the "locking block." An LED-radiant block illuminates from within the upper levels of the podium screen and lower levels of the glass façade. The colors gradually change at dusk from white to cobalt blue. "It's not Times Square," he says. "We wanted to be very, very subtle and not too bright, so it illuminates quietly and uniformly."

In keeping with the active-skin notion, Carpenter's team also designed the peripheral sidewalks to interact with pedestrians. With eight motion sensors mounted 60 feet high on building corners, pedestrian movement is tracked and triggers vertical bars of colored light to project inside the podium skin and move with the direction of the individual -- making the podium a kind of light show for each passerby.

But the beauty of illumination is not limited to 7 WTC's exterior. Carpenter's team also designed the lobby's lighting wall to engage tenants and visitors upon entry and complement the animated-text installation that conceptual artist Jenny Holzer created.

Carpenter and Holzer collaborated on the main-lobby design*

The innovations Carpenter and the architecture team employed in the 7 WTC scheme are part of the tower's overall program to deliver the very latest in architecture and technology to its tenants, and, of course, the community.

"We always recognized that this building would be part of the 'cultural zone,'" Carpenter explains. "It's all about trying to make people aware of the subtleties of information and images that we are surrounded by always, and oftentimes don't acknowledge. The question is how do you heighten the experience to the point where you then begin to recognize that it's something unusual? How do we amplify people's perception?

"[These are] ways for the building to actively contribute to the neighborhood, so that it's not just another building downtown, but a building that has another, richer life to it," he says.

Visit www.WTC.comto learn more about leasing opportunities at 7 WTC.
*Photos by David Sundberg