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Philadelphia Green Roof Embeds Charles Library Visitors in Nature
On the fourth floor of the new Charles Library at Temple University in Philadelphia, visitors will find an unexpected retreat that feels embedded in nature. The sun-filled space, glazed on all four sides with glass, offers views of a lushly planted green roof.
At 47,300 square feet, the sloping green roof covers 70% of the building’s roof surface, making it the second largest in Philadelphia and one of the largest in the state. It’s become a calming foreground for students and community members, while also playing a significant role in the building’s stormwater management system.
A Rain-Retaining Roof
The Charles Library’s roof was designed to capture and retain a maximum amount of rainwater not only from Temple’s campus, but also from Philadelphia’s aging infrastructure, which has been historically overburdened during storm events, notes Scott Sullivan, one of Stantec’s principal architects that worked on the 10-year project.
Photo: Covering over 70% of the building’s roof surface, the 47,300-square-foot green roof is one of the largest in Pennsylvania. It plays a key role in the site’s stormwater management strategy. Credit: Michael Grimm Photography
Stantec developed the building’s design in collaboration with Snøhetta. The international architecture and design firms incorporated the best of modern architecture, along with space- and energy-saving design into Charles Library’s interior and exterior.
The green roof, in particular, was designed to provide benefits for the building both inside and out. According to Sullivan, the library’s stormwater management system includes:
- The green roof
- Pervious paved plazas and paths
- Landscaped planting beds that infiltrate rainwater
Sullivan notes there are also two underground catchment basins that together can store and process nearly 500,000 gallons of water during storm events. Altogether, he says the project manages all rainwater runoff on the roughly three-acre site, as well as for an additional acre of offsite impervious ground.
Creating Natural Habitats
Along with stormwater management, the green roof has become an amplified meadow landscape due to its differentiating soil levels. Sullivan says the fourth floor’s sloping roof comprises both extensive and intensive roofs.
Photo: The new Charles Library opened in fall 2019 at Temple University in Philadelphia, and anticipates over 5 million annual visitors. Credit: Michael Grimm Photography
The extensive portions are very shallow and use only three to four inches of soil. “If there’s a lot of rainwater, [the extensive roof] will slowly release it, otherwise the plants will suck it up,” Sullivan says.
The intensive roofs are on the lower end of the slope. Sullivan says the soil strata here is about 10-12 inches deep, and allows the library to put in traditional plants that one would see on the ground that can grow two, three, four feet tall.
The roof gardens include upwards of 15 different plant species, all of which now provide a rich urban habitat for pollinators like bees and butterflies, notes Sullivan.
“It’s wonderful because then when you’re on the [fourth] floor, you’re looking out onto this green roof with all these plantings, and it’s just a great thing to see all that nature that’s up there,” he says.
Green Roofs Can Lead to Certification
Sullivan adds that the green roof is helping the Charles Library achieve its target of LEED Gold certification. Roofs are a major element to any building that can help obtain a variety of LEED credit categories, including energy and water efficiency. Green roofs, in particular, are an ideal way to earn LEED credits since they are something occupants can take advantage of too.
(Photo: One unexpected bonus of a green roof is its ability to become an Instagram-worthy space. Scott Sullivan, architect for Stantec, the firm that worked on the project, notes that the fourth floor of the Charles Library has become a hot-spot for students to take pictures of the gardens and the occasional praying mantis on the window. Credit: Michael Grimm Photography)
With its modern architecture and impressive roof landscape, the new Charles Library is sure to draw in visitors from both the campus and its surrounding community.
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