American landscape architects and a Canadian nonprofit green roof industry association say that the United States could see a surge in green roof installations if a provision in a recently introduced Senate stimulus bill becomes law.

The Clean Energy Stimulus and Investment Assurance Act of 2009 (S.320) introduced by Sen. Maria Cantwell (D-Wash.) is legislation geared toward creating green-collar jobs and revitalizing the economy through clean-energy investments. But the bill also provides financial incentives for homeowners or commercial buildings that install green roofs on their buildings.

Under section 506 of the bill, residential (as well as commercial property owners) will receive a 30 percent tax credit for qualified green roof expenses. The tax credit applies to both new and retrofit projects, but it requires that at least 50 percent of the roof area be covered with vegetation.

"This is a watershed moment for the green roof industry", says Steven W. Peck, founder and president of Green Roofs for Healthy Cities, which worked with the American Society of Landscape Architects to help Sen. Cantwell's office draft the section of the bill that's focused on the green roof incentive. "This bill will deliver an enormous number of green-collar jobs—not just today, but five years from now—while also saving energy, improving stormwater management, cooling cities, cleansing the air, and beautifying our rooftops."

A green (or sod) roof is exactly what it sounds like: a roof consisting of vegetation—usually drought-tolerant sedums, plants, or shrubs—that's planted in a growth medium. The roof generally involves a multilayer system of waterproof and root-repellent membranes, a drainage system, filter cloth, and lightweight soil.

Green roof advocates say the system offers a wide variety of benefits for homeowners, such as adding insulation to a house and helping to keep the house cool, since the roof isn't getting direct sunlight. But there are other benefits.

"For society at large, green roofs strip the air of pollutants and help with stormwater management," Peck says. "If you install enough in an area, it cools the area, which saves money in energy costs and limits greenhouse gas."

A green roof helps cool urban areas by reducing the "heat island effect," a situation in which dark surfaces—such as asphalt roofs in a city—absorb sunlight and radiate it back into the atmosphere as heat.

Peck says green roofs also help stimulate the economy, because most of the jobs generated from green roof installations happen locally and regionally. "For every dollar spent, the $2 or $3 generated go toward creating jobs where the roof is installed," he says.

"In these times of economic uncertainty, growing the green economy and investing in clean energy technologies is the key to job growth and breaking the United States' debilitating dependence on foreign oil," Sen. Cantwell said in a statement introducing the bill. "While installing a green roof may seem like a small step, these upgrades save energy, filter and absorb pollution, and store carbon. As individuals and businesses continue to look for ways to combat high energy costs and improve the health of their neighborhoods and environment, providing green roof incentives just makes sense."

Meanwhile, Green Roofs for Healthy Cities has launched a new, multidisciplinary Green Roof Professional (GRP) program—much like U.S. Green Building Council's LEED Professional Accreditation—and will administer the first exam at its 7th Annual Conference this June in Atlanta. Under the program, an individual can become GRP-accredited to provide green roof design, products, and installation services to meet the new demands that potentially could be generated from this bill.