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Green Roofs: They can save energy, be a source of beauty
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Published: October 26, 2008
WILMINGTON - When the Fortunas want to enjoy their garden, they climb a flight of green-marble steps that lead them outside where the Cape Fear Memorial Bridge appears at eye level in the distance.
Atop their three-story home, they're standing on downtown Wilmington's most landscaped residential roof. The flat roof bursts with different varieties of sedums, yellow and purple pansies, yellow lantana, lilies and a screen of potted pink mandevillas that hide the heating and cooling system.
The Fortunas are the first in Wilmington to sprout a residential green roof, which soaks up some of the rainwater and keeps their roof much cooler than tar tops.
"It's nice to come up here and have your own private garden," Denise Fortuna said. "It's very calming, especially with the sunsets."
Steve Mott, the owner of Mott Landscaping, planned and planted the Fortunas' roof on the building.
Mott, who has completed classes in green-roof design and installation, also converted part of the roof of his business into a green roof. Although the trees and greenery thriving on Carrabba's Italian Grill may be seen as a green roof, it is not in the traditional sense.
"It's more for decoration but not functional," said Phil Prete, the senior environmental planner for the city. That's because green roofs traditionally are meant to mitigate rainwater runoff and lower temperatures with plants.
Green-roof construction grew by 30 percent in North America last year, according to the 2007 Green Roof Industry Survey by the nonprofit industry association Green Roofs for Healthy Cities.
Mott said the practice of green roofs has been growing in Germany for more than 30 years.
In the United States, the idea of green roofs has spread to cities such as Chicago and New York where developers are offered incentives to go green on top. Chicago boasts 517,633 square feet of green roofs, more than any other North American city.
Wilmington is no Chicago, but Prete said that the central business district here provides perks for green-building techniques, such as density or height bonuses. "I'd love to see a city building with a green roof as a demonstration or to lead by example," Prete said. "Maybe one day, who knows?"
A green roof had been included in the original plans for Wilmington's convention center, but the idea was eliminated because of the project's rising cost.
Commercially, developer Ron Pickett said he would like to build a green roof on the 11-story garage included in his Gateway project for aesthetic as well as environmental reasons.
"I intend to have several green features with this project," he said. "It just doesn't make any sense not to think economically green. I'm combining the two. The cost of that roof is worth it to the project for the enjoyment of the people."
The county is also moving in the direction of green building as commissioners recently approved a manual that gives developers alternative ways to manage storm-water runoff and provides tips for going green. Green roofs are included in the manual.
Benefits of a green roof are reduced rainwater runoff that leaks pollution into creeks and rivers, lower roof temperatures, decreased temperatures overall in a city, prolonged roof life, lower energy costs, and of course, a pleasant-looking place with plants, experts say.
"What causes roofs to fail is ultraviolet light and major temperature fluctuations," said Bill Hunt, an assistant professor and extension specialist in the biological and agricultural engineering department at N.C. State University. He researched green roofs in North Carolina and tested their water-retention capabilities. "The plants basically absorb the temperature."
Mostly, green roofs make sense in urban areas where space is limited.
"What they don't do is reduce runoff if it's a really big storm," Hunt said, adding the roofs he researched absorbed half of the water. "If you get a hurricane, for example, you're not going to see a huge benefit of a green roof."
In North Carolina's suburbs or rural areas, more efficient and cost-effective methods exist to retain rainwater, such as permeable pavement and rain gardens, he said.
Then, there's the issue of how much green is a green roof worth?
Shannon Rippy, the manager at Mott's, said that it can cost anywhere between $10 and $20 a square foot depending on a garden's depth and type of plants used.
But the long-term benefits could be worthwhile. "It can double the life of a roof so replacement costs can be cut significantly," Prete said. "It can cut your heating and cooling costs."
It's too soon to tell how much the Fortunas will save on energy costs, but observing nature in their urban environment is priceless.
"We've had everything, hummingbirds," David Fortuna said. Denise Fortuna continued: "Snails. Butterflies. It's a little eco-system."
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