CHESTERTON -- Face it, roofs are a hassle. They leak and collect gutter debris. They're expensive to maintain and replace. And they're no friend to the environment, adding to urban "heat islands" and floods of stormwater runoff.

But imagine roofs that cut energy costs, cleanse the air, reduce flooding and last a long time.

A meadow-like building top in Chesterton may hint at this radically different future.

A "green roof " -- one planted with native grasses and drought-resistant succulents-- sits atop the restroom facility by the visitor pavilion at Chesterton's Coffee Creek Watershed Preserve.

Featured in the summer issue of Chicago Wilderness magazine, the roof is a modest several hundred square feet, but it is at the cusp of a potentially huge rethinking of the high spaces that are generally out of sight, out of mind.

From energy efficiency to environmental cleansing, the seeded coverings offer a field of advantages over a standard asphalted or shingled roof.

But perhaps their greatest value will be found in reducing the increasing amounts of stormwater run-off that whisk pollutants and -- during heavier rains -- the raw waste of combined sewage overflows into drinking water sources.

And their drawbacks?

"I can't think of any, honestly," says Jay Womack, a landscape architect with Conservation Design Forum of Elmhurst, Ill., which designed both the Coffee Creek roof and the showcase roof atop Chicago's City Hall.

One downside is that a green roof can cost twice as much or more as a standard roof, depending on the type of building and whether it's a retrofit or a new installation.

But while the standard roof lasts an average of 15 years, many industry experts in the United States say a green roof can last 30 years.

The reason is they never experience the damaging effects of sun, wind, water and ice. The green layer is like a large living blanket.

Steve Barker, director of the Coffee Creek Watershed Conservancy, says he has experienced no problems or leaks with the four-year-old roof there. He occasionally goes up to weed, but that's about it. And the public reaction has been mostly one of fascination, he said.

Most green roofs are planted with sedums, low-growing succulent plants that are shallow rooted and can tolerate dry conditions. The coverings incorporate up to nine layers and range in depth from 3 to 18 inches. Among the layers are an impervious liner and a root barrier that keep moisture and roots from doing damage to the building.

The growing medium is often a non-organic material that is lighter than standard soil. Green coverings generally add only about 25 pounds per square foot to a roof's load, even when wet, well within the 90 pounds that most roofs can support, Womack says.

At Indiana Dunes Environmental Learning Center in Porter, an 11,000-square-foot education building with a green roof among its energy efficiencies has been on the drawing board for four years but is still "several million dollars away," says director John Hayes.

Brian Williams can be reached at bwilliams@nwitimes.com or (219) 462-5151, ext. 348.