By STEVE BINDER
Illinois Correspondent

CARBONDALE, Ill. — For an unfiltered, statistical look of the impact of a “green” roof, all one has to do is check the weather log from Southern Illinois University Carbondale’s agriculture building for April 10.

The weather station atop the roof on that day recorded an air temperature of 91 degrees as the high, part of an early spring mini-heat wave for southern Illinois. But the temperature of the bare roof adjacent to its green portion, was recorded at a sizzling 140 degrees.

And the temperature of the roof’s portion right below its green layer? A cooler 81 degrees.

“I almost couldn’t believe the numbers when I saw them. I certainly did a double-take,” said Todd Winters, interim dean of the school’s agriculture college.

The new green roof, installed in September 2010, enters its first spring and summer seasons garnering a lot of attention on campus.

It was the focus on the first day of the college’s Ag Industry Days last week, and attracted some 350 people for tours.

A variety of wildflowers and grasses, a large sedum carpet and some garden vegetables were planted last fall; students began planting tomatoes for the first time last week. Among the more exotic plant varieties are wild columbine, harebells, heath aster, blazingstar, cinquefoil and beardtongue.

While not large, at roughly 3,000 square feet, the greened portion of the flat roof not only offers economical benefits, but will be a sustained learning laboratory. “This is our outdoor classroom,” said ag professor Karen Midden. “I wanted students to have a demonstration green roof as a studying tool.”
Students will continue evaluating different species for drought tolerance and other aspects that affect the growing popularity of green roofs. They also are tracking the performance of different growing media, including clay, slate, lava rock and pumice. Researchers also will gauge the performance of several fertilizers.

The numbers of green roofs throughout the United States are growing, based on documented benefits such as reduced heating and air conditioning costs, storm water runoff management, pollution reduction and oxygen production, extra sound installation and the doubling of a roof’s lifespan.
SIUC’s project was funded with a $20,000 grant from a student “green” fee in addition to contributions of $10,000 from Winters and $10,000 from the university’s physical plant budget.

Three main sections of the ag building’s roof now are green, with a growing base of about three inches.

The makeup easily falls under the maximum 25 pounds per square foot that the roof can support, Winters said.

To view the roof’s data from its weather station, go to www.hobolink.com/p/ 5ac7c22fcaa4f1be5292648793214121