No Lite Job: Massive Glass Panels, Transparent Structures Revive Historic Philly Landmark

dillworthproject“From the beginning, the idea was always to set up a front door for city hall.”

That’s how KieranTimberlake principal Richard Maimon describes the thought process behind the design of the newly renovated—check that, completely overhauled—Philadelphia Dilworth Plaza, now known simply as Dilworth Park.

The park, which opened earlier this fall, sits in front of Philadelphia’s City Hall. Below it is a transportation hub that joins the city’s subway, regional rail and trolley lines, which are now coherently connected thanks to the $55 million project.

A major part of the design is the updated entrance to the transit network, which is now housed by two large 17-foot-wide, nearly 20-foot-high glass pavilions that act as entryways.

“The transparent pavilions, counterpoised to the north and south of the central artery, appear to emerge from underground and are joined through a single arcing gesture that frames views of City Hall,” reads a description from KieranTimberlake. “Whereas before the concourse was dim and unwelcoming, the transparency of the glass allows light to flow into the new concourse, which is reorganized to provide clear and unencumbered access to public transportation.”

The structures are stunning, though they were designed very carefully as to not take away from what was already there—the historic City Hall building.

“Views of City Hall were important,” says Maimon of his desire for the shelters to be “as transparent as possible.” He says the manner in which the pavilions were linked visually by a single arch in framing City Hall “suggests a grand scale, but the pavilions themselves are not on that scale.”

“Glass really was the way to go.”

Maimon worked with glass engineer Dewhurst Macfarlane in the design phase and Eckersley O’Callaghan in construction to create the all-grass structures without hardware or metal to preserve the “uninterrupted” view of their surroundings.

“The glass pavilion adds a kind of transparent sculptural presence to the park, allowing an elegant welcoming entrance to the low grade while providing daylighting,” says Maimon. “The pavilions essentially act as skylights to part of the concourse.”

All in all, 92 total lites of glass, amounting to approximately 5,000 square feet, were used on the project.

APG International installed the Pilkington glass, which was cut, edged and tempered by General Glass International (GGI) and fabricated by European Glass Laminators. All three companies are headquartered in New Jersey.

The vertical wall panels were five-ply, and the roof panels were seven-ply—and designed to handle all the loads of a conventional roof. Thirty-six of them were approximately 3,000-pound roof panels, with the largest wall panel spanning nearly 19 feet.

“Weight-wise, it was like doing a whole building,” adds APG project manager Sherman Hartman.

The larger panels that had to be produced were “jumbo” lites, though European Glass Laminators project operations director Tony De Witt says that the particular lites used for this project were unique in that they were the European standard for jumbo, which is 6-by-3 meters (20-by-10-feet). The jumbo standard in the U.S. is a foot narrower, according to De Witt.

Pilkington produced the large lites, shipping them to GGI to process before they were sent to European Glass Laminators for fabrication.

APG set in the first piece of glass May 8, 2014, two years after getting the call for the job, of which Hartman says the “specifications and tolerances” were one of the more challenging aspects.

He describes the project from an installation perspective: “The walls themselves are trapezoids. They’re set at an angle. The top is basically square, and the bottom is at an angle … Everything is on a 20- to 30-degree tilt.”

The lower three layers of the vertical pieces are set in so the roof panel and wall panel can tongue and groove together, and according to Hartman, the top is held together with structural silicone.

He adds, “At the base is a custom stainless steel shoe we had built, and inch and quarter of thick stainless steel. That’s what holds the walls in place.”

The project was made possible thanks to several grants—on the federal and state level—as well as capital from the city of Philadelphia and a variety of private foundations. The site is owned by the City of Philadelphia under a lease agreement with the Center City District.