Volume 50, Issue 11 - November 2015

Eye to the Sky
Operable Skylight Brings “Oculus” Transportation Hub to Light

by Nick St. Denis

The New World Trade Center Transportation Hub features a 330-foot operable skylight that runs the length of the concourse.

Manhattan is getting another new landmark this year—and once again, glass is involved.

The new World Trade Center Transportation Hub, designed by Santiago Calatrava and owned by the Port Authority of New York and New Jersey, serves as a welcoming gate for people arriving by subway or commuter train, but it is much more than that.

The entrance and roof enclosure of the terminal is a large, freestanding, steel-and-glass shell dubbed the “Oculus,” which features steel ribs that extend upward beyond the structure’s main enclosure and is fitted with glass—lots of glass.

A 330-foot operable skylight, running the length of the entire concourse and spanning up to 12 feet wide, joins the two “wings” and allows for ventilation and passive conditioning of the space below, according to façade consultant Heintges & Associates.

More than 200 lites of glass were used on the skylight, and nearly 1,000 lites in all were applied to the entire structure.

The Glass

Nearly 1,000 lites of blast-resistant glass were used on the Oculus. Two hundred and twenty-four were used in 40 panels on the skylight. The rest of the glass, supplied by Eckelt and installed by Enclos, sit between the many ribs on the structure.

“The complex shifting geometry of the skeletal structure made of steel ribs dictates that nearly every steel rib and lite of glass is a slightly different shape,” according to a description from Heintges & Associates. “Atypical construction sequences [were] employed during installation. The curtainwall and skylight systems are designed to accommodate a complex set of performance criteria, with special attention paid to security and energy efficiency.”
Much of the glass is 1.65 inches thick, with the larger lites upwards of 13-by-5 feet in size.

Bring in (and out) the Light

The sunlight allowed in through the enclosure provides natural light even all the way down to the train platforms, approximately 60 feet below the ground.

When the sun goes down, the light makes a 180-degree turn.

“[A]t night, the illuminated building will serve as a lantern in its neighborhood,” says Calatrava on the firm’s website.

Long Time Coming

Calatrava unveiled the design for the transportation hub back in 2004, proposing an operable roof that could pivot open entirely. According to the New York Times, the operable roof was removed from the plans in 2008 due to cost, and a retractable skylight would instead be installed.

According to the architect, it “frames a slice of the New York sky” from inside and will open on temperate days, as well as annually on September 11.

“A Different Ballgame”

Mic Patterson, director of strategic development at Enclos’ advanced technology studio, says kinetic structures such as the Oculus have become popular in recent designs.

Enclos is working on a handful of such projects within its Kinetics division, and it is pursuing others.

“It is a different ballgame, combining facade and skylight elements with structural systems designed to move, and again with the mechanical equipment that controls that movement,” he says. “Contemporary facade systems often present ample challenges in themselves; requiring them to move can multiply those challenges by an order of magnitude.”

Architects remain interested, despite the challenges.

“In addition, there are many facade practitioners suggesting that true high performance in the building skin will require the integration of dynamic elements capable of responding to changing ambient climate conditions,” says Patterson. “Kinetic systems are a potential vehicle for this kind of dynamic.”

The systems require careful planning and early collaboration. With the Oculus project, for example, Patterson says Enclos had “extensive pre-sale involvement in this project,” starting approximately two years before being awarded the job.

the author

Nick St. Denis is an assistant editor for USGlass magazine.
He can be reached at nstdenis@glass.com.

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