Covered by soil and vegetation and serving a number of environmentally friendly functions, a green roof merges architecture and the natural world.
The biggest incentive to installing a green roof is insulation. Local green roof installer Sam Gilpin of Charleston Green Roofs claims, “It will keep the structure cooler in the summer and warmer in the winter, saving money in the long run.”
These eco-roofs will also help in stormwater management, Gilpin says. “They reduce water runoff by absorbing rain and keeping it from washing across land, picking up toxins and pollutants.” He says the water can even be collected for gray water use.
Green roofs have become quite popular in European cities. The roofs can have a significant environmental impact in lowering the air temperature in a city. “A typical roof will reflect heat,” Gilpin explains, “while a green roof will absorb heat.”
Buildings that support green roofs start with a waterproofing and root repellent on top of the actual roof. The next step is a drainage layer, leading upwards to a filter membrane. Next comes the soil, and finally, the plants. Gilpin says a green roof will cost about $4 more per square foot than a traditional roof.
When I visited Bowens Island Restaurant and looked at the brand-new green roof Gilpin built over owner Robert Barber’s office, I was surprised to see that the roof wasn’t as green — as in the color — as I had expected. The soil looks very rocky, almost desert-like. There is no traditional grass; instead there’s “clumping grass,” which is more like a plant and does not need mowing. The biggest surprise was that there are not as many plants flourishing as expected. This is because, at the beginning, the structure needs to grow and mature. He likens the growing medium to “lava rock.”
In the five inches of soil atop Barber’s office, there are 17 different types of plants. Gilpin chose to use low-maintenance vegetation. He explains, “We get a lot of storms, it can be windy, and of course, very hot in the summer while also getting cold in the winter.”
Despite that, Gilpin believes there is a market for green roofs here in Charleston and that one day they will not be an anomaly.
“As the technology grows, and more structures are built to hold green roofs, eventually, I think they will be a lot more common,” he says.