BALTIMORE - Atop the National Aquarium in Baltimore, away from the crowds, is a hidden oasis where the turtles and lizards sometimes come to bask in the sun. Their caretaker says it's also a nice spot for wild birds - and him, too.
The 4,000-square-foot "green roof," a 4-inch deep collection of soil and succulent plants over a rubber liner, has been serving many purposes since it was built in 2004. Besides acting as an urban refuge, it's helping cut utility bills and control rainwater into the harbor.
"This is good for everybody," said John Seyjagat, curator of the Australian exhibit and the green roof. "Instead of blacktop, why not make it pretty?"
The aquarium built the roof because of its conservation mission. But it isn't the only city building shedding black for green. Offices, hotels and residences are now planting on their roofs, recognizing the benefits that may include storm-water management, lower energy bills, better air quality, good looks and even food production. As at the aquarium, most are largely made up of sedum plants, drought-resistant ground covers with water-absorbing leaves.
Baltimore is emerging as one of the nation's greener roofed cities, with approximately 150,000 square feet added last year, or the nation's fifth-most, according to Green Roofs for Healthy Cities. The advocacy group doesn't have totals for each city, but estimates that square footage is up about a third from 2007, nationwide. There are at least 20 green roofs in Baltimore, including Sinai Hospital's 1,050-square-foot roof garden on its new eco-friendly addition. There's a 5,500-square-foot roof on a BP gas station. And the Maryland Science Center plans to build a 4,000-square-foot green roof that will be open for public viewing.
Many cities support the effort with tax breaks or other incentives, said Steven W. Peck, founder and president of Green Roofs for Healthy Cities. They include the green roof leader Chicago, with almost 535,000 square feet, and New York, with slightly more than 500,000 square feet. Baltimore does not offer cash incentives, but has been encouraging the trend through some horse trading, said Beth Strommen, manager of the city's Office of Sustainability.
The roofs reduce runoff, so the city can approve them as alternatives to potentially more expensive and elaborate storm water management systems. And, she said, "They help us with the heat island effect because they're cooler than traditional roofs."
The Fairfield Inn & Suites and the Baltimore Hilton Convention Center Hotel both got waivers. At the Hilton, which has a city-leading 31,000 square feet on two green roofs, the project meant managers did not have to build a $175,000 underground storm-water management system. In the end, the roofs cost about $350,000 but are expected to improve energy efficiency and "aesthetically make the hotel guest experience so much nicer," said Irene Van Sant, of the Baltimore Development Corp.
, and the project manager for the publicly financed hotel.
Other property owners didn't need city prodding. The Herring Run Watershed Association built its roof as part of its effort to earn LEED certification, the gold standard of environmental building, which can bring tax incentives, energy savings and aesthetic improvements.
Samuel K. Himmelrich Jr., who redeveloped the old Montgomery Ward building in Southwest Baltimore into the Montgomery Park office complex in 2002, said building two of the city's largest green roofs was costly. And he can't say how much he's saved in energy costs because he never operated the building without the roofs. But he said their strongest benefit has been luring and keeping tenants, including the Maryland Department of the Environment.
"At the end of the day, the roofs count toward the appeal of the building," he said. "Everyone who comes to Montgomery Park speaks about them and enjoys them. I would do it again. In fact, I have another building where we're looking at it."
Richard Jones, who is an associate principal at the landscape architecture firm Mahan Rykiel, said the roofs vary in costs. "Extensive roofs" average $15-$20 a square foot and are a few inches deep with soil and vegetation designed to meet water or energy management goals. A 4-inch depth can hold half to 70 percent of the rainfall.
"Intensive" roofs start around $50 a foot depending on the level of finish. They often require deeper soil to handle more dense planting and are typically spaces occupants use. And while the cost can be significant, the benefit of more green space is invaluable to many.
Despite the upfront costs, the roofs are often cheaper for building owners in the long run because the roofs have to be replaced far less frequently, and they help the buildings stay warmer in winter and cooler in summer. But Jones has another explanation for the proliferation of green roofs.
"People are moving from the suburbs where they had gardens and parks," he said. "In the city, the amenities are not always easily available, and roofs offer that space. Baltimore is also experiencing a lot of revitalization. ... And the city is ripe for new technology and proactive about being environmental."
To help those considering a green roof figure out costs verses benefits, Green Roofs for Healthy Cities added a GreenSave Calculator to its Web site.
Each situation is different because, for example, some cities have storm water fees or incentives, and roofing systems vary in size and costs. The group anticipates more cities will encourage the roofs and has launched a professional accreditation program so those hiring designers and contractors can know they have specific training.
"Ideally, we'd like to see buildings providing more resources than they take, but we're very far away from that," he said. "Green roofs are a start. And I wouldn't call it a trend. We are seeing the beginning of a transformation in the building industry."