By Paul D. Kretkowski
Welcome to the new 7 World Trade Center, where the artwork is a blast shield, the roof waters the park, the park holds the fuel tanks, and the lights follow you.
Oh, and the security turnstiles call you an elevator.
After 9/11 and the destruction of the old 7 World Trade Center, Silverstein Properties hired David Childs and Skidmore, Owings & Merrill (SOM) to design a successor building that made statements at several levels: urban design, architecture, life safety, and sustainability. The resulting $700 million, 52-story structure is dramatically safer than code requires, energy-efficient, and pleasant to work in, not to mention a technological powerhouse that uses technology in ways many could only previously dream about.
CEO Larry Silverstein "didn't want to build a fortress," recalls Silverstein Properties marketing and communications director Dara McQuillan from his office in Seven, as everyone calls the new building. "He figured no one would want to work here. So he asked people to make it as transparent as possible with the use of glass, [and think] what it would be like from a human perspective, going in and out of the building every day."
For example, one urban-design goal - opening up Greenwich Street to connect TriBeCa and the Financial District - meant a smaller building footprint than the old Seven, but as SOM partner Carl Galioto says, this "restriction" also created space for a 15,000-square-foot urban park and a secure environment for the fuel tanks for Seven's emergency generators.
"We used the footprint of that park to increase the building's safety in two ways: One, we buried all the fuel-oil tanks out there so they're outside the footprint, and two, we created a standoff distance from the entrance of the building to the street, which is on the opposite side from the park," Galioto says.
"The trees, the benches, all of those things are a hindrance to a vehicle moving," adds Nicholas Holt, associate partner at SOM and senior technical architect on the project.
Building and Life Safety
Of course, safety concerns were paramount at the relentlessly scrutinized World Trade Center site.
Seven is designed to resist progressive collapse via moment-connected frames and floor plates. "It's all in the framing members and girders and how they're attached to the columns; the beams will locally collapse but not create a collapse that extends to the whole building," says Holt, adding that the building uses alternate load paths for redundancy.
For fire safety, construction crews applied fireproofing material to Seven's frame that is seven times more cohesive and adhesive to the underlying steel than required, Holt says, greatly improving survivability in fires or impacts. "The issue with fireproofing, if you'll recall from the World Trade Center [fires], is that it would come off the steel, so it's the ability to adhere to the steel that is the issue."
Exit stairs are 20-percent wider than code requires to enable first responders to access the building without interfering with exiting tenants. Emergency command is unified at a Firecom fire-command station at the lobby desk. All building fire alarms connect to it, and the station also shows the positions of all dampers and whether they are operating. If the lobby station is compromised, fire crews can use a redundant system at Seven's loading dock.
The need to evacuate speedily drove improvements to Seven's electronic life-safety systems. "The issue in [the Trade Center towers] was confusion," says Holt. "There were conflicting instructions delivered by the building staff: One person said, 'Evacuate,' another said, 'Go back to your floor.'"
Seven addresses the confusion problem by instituting structural improvements and a greater emphasis on unified messaging. The building's four stairwells are protected by 2 feet of concrete and can be pressurized to repel smoke and other contaminants, reducing chances of both panic and impaired visibility. They also feature an innovative electronic signage system driven by lessons learned from 9/11, developed by security engineering firm Ducibella Venter & Santore.
As expected, Seven's life-safety system generates code-required voice cues, strobe lights, and sirens warning tenants of hazards. Beyond code, the stairwells use a system of unified messaging via electronic signage. Trained building fire safety directors (FSDs) operate the system from control centers in protected transfer corridors that are equipped with video feeds of stairwells, exits at grade, and the lobby.
FSDs can notify evacuees of problems - blockage of one or more stairways, for example - using standardized messages instructing evacuees to use a transfer corridor to reach an alternate stairwell, or to shelter in place if there are greater threats outside. Red or green lighted chevrons display a redundant message, which also aids non-English speaking or illiterate evacuees. As evacuees traverse the transfer corridors, they can view the feeds at the FSD stations to verify they are moving toward greater safety.
Seven has high-efficiency filters at its air intakes, which are 100 feet above grade and at the top of the building, reducing an outsider's ability to contaminate interior air. Both Seven's filtration and its air-intake placement depart from standard practice, Galioto says. "Code says you take outside air and you pump it in, no matter what the condition of the outside air is." He adds that Seven's intake placement anticipates future New York building code, saying that already "the site-design criteria for the WTC site indicate that air intakes must be at least 40 feet above grade."
Utility Con Edison urgently needed to replace its utility substation, which formed the base of the old Seven. A 75-foot-tall substation forms the base of the new Seven as well. It requires 50-percent open louvers for cooling, and SOM called for two layers of high-precision, stainless steel filtering screens to both cool the facility and provide blast resistance.
Seeing the opportunity for a creative cue, SOM embedded blue and white LED fixtures within the screens. Software ties their lighting pattern to motion sensors aimed at the sidewalk, and only sharp-eyed pedestrians notice that a 5-foot-wide, lighted blue stripe may follow them as they walk beside the building. "You'll see these totally unsuspecting people walking down the sidewalk and a crowd of people standing up the block going, 'Oh, isn't that neat,'" Holt observes.
The building's podium light display system was developed by James Carpenter Design Associates (JCDA), while the exterior LEDs were brought to life by LED Effects Inc. JCDA also designed (and Permasteelisa's Gartner division built) a cable-net entry wall for Seven's lobby that is not only elegant but also blast-resistant, protecting those inside at the elevator lobbies.
New York conceptual artist Jenny Holzer designed an animated-text installation for Seven's lobby: a 65-foot-wide, 14-foot-high, blastproof glass wall that displays continuously scrolling New York-centric prose and poetry by E.B. White, Allen Ginsberg, Walt Whitman, and others. The text scrolls across the wall, which is actually 13, 5-foot-wide glass panels, courtesy of an LED system suspended between two panes of glass in each panel, and is controlled by electronics that generate characters in a variety of fonts. Text characters appear to float when viewed from either the front or the back and are remarkably clear, even to passersby outside the building; each panel's glass is acid-etched and laminated with Sentry Glass Plus, while edges are satin-polished to cancel any internal reflections generated by diodes. The LED display was manufactured by Pembroke, MA-based Sunrise Systems, while Allied Bronze created the glass wall itself.
Nine plasma screens fit together to display the future of the World Trade Center. A frame, which sits about 15 feet from the actual 63-inch screen, acts as a mouse. Sensors read the hand movements of the user as she puts her hand through the frame - commanding either images or video.
The drive for LEED recognition developed during SOM's discussions with Silverstein Properties. "We wanted the safest high-rise in New York ... and also to have something which made a major sustainable- design statement," SOM's Galioto recalls.
SOM participated in a pilot program that helped develop the new LEED Core and Shell certification. It focuses on reducing environmental impacts from the building exterior's construction and maintenance while de-emphasizing interiors - but requires building owners to encourage tenants to create LEED-compliant interiors. Seven's LEED Gold Core and Shell certification is the first in Manhattan.
One factor in attaining this certification is low-iron, floor-to-ceiling, Viracon VRE15-59 glass windows that let daylight stream into 90 percent of the building's interior, reducing interior lighting needs. The double layered glass's low-emissivity coating and sprayed-on ceramic frit combine to control heat transmission and stop certain ultraviolet frequencies. Its unique reflective properties can make Seven seem rock-solid or appear to blend in with the sky, depending on the observer's angle.
The building must also reduce the pressure of steam it draws from New York's extensive but very high-pressure steam lines. Rather than call for a simple valve to do the job, SOM specified valves with microturbines that convert steam into a small amount of electricity while reducing pressure to a usable level. The point of the microturbines was not that they would generate a significant amount of power in this building at this time, but that using them would inspire further technological development and adoption - a major goal of LEED. "We tried to take advantage of every opportunity where energy enters the building, or moves through the building and is being wasted," Galioto says.
Another feature that earned a LEED point for Seven is that the building captures rainwater from its roof to cool the building and irrigate the street-level park. Water captured from the roof is held in a storm water tank within the tower and then gravity-fed into cisterns beneath the park that total 52,000 gallons. The water is also available for use as makeup for cooling the building, with the added benefit to New York City that this system decreases storm water runoff by 25 percent.
Marriage of Security and Elevator Systems
Seven's elevators use an innovative "destination dispatch" system: After tenants swipe their ID cards at the lobby security turnstiles, the turnstile indicators direct them to a particular elevator. "It groups passengers by their floor, which can be significantly more efficient than your standard up-down buttons," says Holt. (See Prime Time for 'Destination Dispatch,' in the sidebar.)
Once users are in the elevator, an Elite PI video screen provides information about what floor they're on as well as building announcements. This smooth transition of the elevators communicating with the security system and then with passengers makes the tenant experience seamless, and is typical of the attention to technological detail that Seven's visitors are bound to notice.
As this building fills with tenants and draws more attention, it is more likely than ever to serve not just as the keystone for several other major World Trade Center buildings, but also as a model for what New York and other cities' building codes will become, and what thoughtful design integrated with leading-edge technology can achieve.