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Glass Building Planned For Downtown Philadelphia
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Exterior rendering of the new building features an extensive use of glass and structural folds
The new building to be constructed at the corner of Walnut and 15th streets in downtown Philadelphia features an extensive use of glass and structural folds to create an inviting, dynamic presence. Bohlin Cywinski Jackson Architects

A new glass-clad building will provide refreshing transparency in a city dominated by masonry structures.

May 14, 2013—A new retail building planned for downtown Philadelphia is sure to be a standout. Nestled among the city’s burly masonry structures, the three-story building will be clad in ultraclear glass and provide a transparency that is otherwise uncommon in the city’s shopping district.

The building, which has no formal name, will replace three existing structures at the corner of Walnut and 15th streets in an area designated in William Penn’s 1682 plans of Philadelphia as Center City, which includes the city’s central business corridor. The Philadelphia office of the architecture firm Bohlin Cywinski Jackson is designing the structure for Midwood Investment & Development, a real estate investment firm headquartered in New York City that owns several properties in downtown Philadelphia, including the building that houses the city’s downtown Apple Store, which was also designed by Bohlin Cywinski Jackson.

At approximately 59,000 sq ft, the new building will have four leasable levels, three above grade and one below. Each above-grade level will have 20 ft of clearance from floor to floor, creating an unusually tall three-story building that will measure 65 ft from the sidewalk to the roof, says Andrew Moroz, AIA, a senior associate for Bohlin Cywinski Jackson. He adds that because it will replace three existing structures, the building will offer retail spaces up to 80 ft wide, a rarity in downtown Philadelphia where most of the retail-oriented lots are just 30 ft wide. The Cheesecake Factory, a restaurant headquartered in Calabasas Hills, California, will occupy the building’s second level and serve as the anchor tenant. No announcements have been made yet about other tenants.

Several factors influenced the building’s design, including the intended use and location of the structure. The glass cladding will emphasize not only the merchandise of the retail stores inside but also the circulation patterns that are unique to such entities. “There are certain patterns of movement found in a retail store that would lead you to a different kind of envelope than for other uses,” Moroz explains. He adds that the intention is to highlight the “nature of the shopping experience, the sort of spectacle of it.” The fact that the building will be surrounded by much taller masonry buildings led the designers to glass as a way to draw attention to the building and connect with people on the streets. The building is “going to enliven the streetscape just by the fact that the activity inside is observable and that there will be some amount of spill light coming out of there,” Moroz says. 

An exterior rendering of 3 structures that will be demolished to make way for the glass building in Philadelphia

Like many structures in downtown Philadelphia, the three that will
be demolished to make way for the glass building in Philadelphia
present a somewhat formidable front. Bohlin Cywinski Jackson
Architects

Designers initially considered cladding the building from floor to floor in laminated glass panels to create a flat, smooth effect. But after further consideration, they opted instead for a system that creates recesses within the facade, giving the building depth while maintaining a sleek appearance, Moroz says. To that end, the facade will fold back approximately 4 ft at certain locations, creating rectangular forms that will appear as though they can slide back and forth on the exposed structural beams that support them. “Those returns in the glass express [their] own materiality even though it’s clear,” Moroz says. “We think this treatment will be very distinctive.”

The building owners had planned to fill in the existing buildings’ basements and construct the new building on the existing foundations. But the existing foundations could not be used in that manner, so at the recommendation of the design team the owners decided to excavate the site of the center building, which does not have a basement, and construct a wholly new foundation to create an additional level of leasable space, Moroz says. The remaining challenge is that the existing building on the corner of Walnut and 15th streets lacks a conventional foundation wall and instead has a rubble wall that extends beneath the sidewalk for the length of the building. The sidewalk braces that wall and keeps the street from caving in, but once that wall is removed, the construction team will have to figure out how to tie the street back without interfering with underground utilities or the new building structure, Moroz says.

The building’s roof is being designed to meet Philadelphia’s new stormwater regulations. (See “Philadelphia Proposes Ambitious ‘Green’ Infrastructure Plan,” Civil Engineering, June 2009.) The city requires that 20 percent of the rainwater that lands on a new building be kept out of the storm-water system entirely and that the first inch of rain be kept on or within the building for 72 hours before being released into the system. “Philadelphia has one of those older … storm and sanitary waste systems, and they’re kept separate, but when there’s a storm surge, it can’t handle the volume, so untreated sewage ends up going places you don’t want,” Moroz explains. “The way the water department wants to manage the surge is to simply have more controls on the storm-water component and slow it down so it doesn’t overwhelm the system.” To that end, 20 percent of the building’s roof will be vegetated to capture a great deal of the rainwater and the remainder will be a ‘blue’ roof, meaning it will retain the water before slowly releasing it into the storm-water system.

Demolition of the existing structures is slated to begin within a month and construction of the building is expected to take approximately 14 months. Moroz says he hopes the building not only produces income for the owner but that it also energizes Philadelphia’s downtown. “Really, in our hearts, we want the building to contribute to the life of the city,” he says. “And if it does that, it has satisfied the owners by creating a building that tenants want to be in.”


 

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