The 12 institutions of the Big Ten conference are making a significant impact on the world each and every day. Watch the newest Big Ten Network program, "Impact the World," which premieres at 9:30 p.m. EST January 10.

More Information »

EAST LANSING, Mich. — Green roofs are bringing dead spaces to life in increasing numbers.

“The green roof industry is growing rapidly,” according to Brad Rowe, a Michigan State University horticulture professor and chairperson of the Green Roofs for Healthy Cities Research Committee. “The area covered by green roofs increased 80 percent between 2005 and 2006 in the United States.”

A green roof study published in the November edition of Bioscience looks at some of the ecosystem services that they provide.

Five years ago, the North American green roof trade show was held in a parking garage with cars driving by, Rowe said, one of the authors of the study. “Last year, the trade show was the real thing, with companies representing 25 countries in attendance.”

Green roofs are catching on in the United States, because research shows that adding green spaces on top of urban areas has economic and environmental benefits.

A green roof is a covering made of living plants and the materials that they need to grow. It is a complicated covering.

Rowe uses different species of Sedum, a small native plant that grows on rock outcroppings “for its ability to adapt to the heat and droughts that occur on top of a roof.” In addition to Sedum, a variety of flowers and grasses can be planted.

The growth material is composed of layers on the roof to make it waterproof, insulate, drain and to grow plants. The depth of these layers is usually between 4 inches and 2 feet. These layers are significantly heavier than a traditional roof, which makes installing a green roof on an existing building complicated and expensive.

One of the factors slowing growth is cost. A green roof costs twice as much as a conventional roof upfront, but “if you look over the lifespan of the roof it is much cheaper,” Rowe said. And, green roofs last two or three times as long as a conventional roof and are more energy efficient.

One major service green roofs provide is storm water retention. Green roofs can retain a portion of the storm water that would normally run off a roof and help prevent flooding.

“In our studies on campus, green roofs retained 60 percent of all the rainwater that fell on them over a two-year period. Even during heavy rains, the runoff is released over a longer period of time,” Rowe said. The layer of plants shade and insulate the roof, making heating and cooling buildings more energy efficient.

For example, based on data from other studies, the green roof on a portion of Rowe’s office building on campus is estimated to reduce cooling costs by 50 percent.

Green roofs also reduce the heat island effect in cities. This effect, caused by city structures absorbing and holding heat, causes cities to be warmer than the surrounding areas by as much as 10 degrees.

Green roofs increase biodiversity.

“A green roof won’t support a water buffalo, but it will support many types of birds and insects,” Rowe said. “In England, people use green roofs for bird habitat.”

On top of the Ford Motor Co. plant in Dearborn, a beekeeper collects honey from the bees that live on the 10-acre green roof.

The study was funded by the Natural Science and Engineering Research Council of Canada.

###

Michigan State University has been advancing knowledge and transforming lives through innovative teaching, research and outreach for more than 150 years. MSU is known internationally as a major public university with global reach and extraordinary impact. Its 17 degree-granting colleges attract scholars worldwide who are interested in combining education with practical problem solving.