A new kind of shingle is taking root on roofs

IPSWICH -- When plants start growing atop a building, it usually means it's time to get a new roof. But at the new housing complex for seniors next to Ipswich Town Hall, the grass is the roof, and the thicker the better.

A green roof without shingles will be taking root this winter on top of the 10-unit complex that the North Shore Housing Trust is building on the banks of the Ipswich River in the former Whipple School Annex. It is an earth-friendly installation designed to protect the river and the building, according to those working on the project.

``It's like putting a blanket on the roof," said architect Ken Savoie, who lives in Ipswich . ``With a green roof, you don't have the high temperatures, you don't have the ultraviolet rays, you don't have all the elements that can do so much damage to a roof."

You also don't have as much rain washing off of it, and in these parts of the Ipswich River watershed, that's a big plus. A green roof is more than a natural alternative to tar paper and shingles; it also is an effective means of curbing polluted runoff, one of the biggest environmental problems facing communities across the country, Savoie and others have said.

This helped the project gain a $110,000 state grant that covered the installation costs. The state Department of Conservation and Recreation approached the North Shore Housing Trust about installing the roof, using money from a federal grant dedicated to improving rain run off conditions throughout the state.

The green part of the roof, where seedlings were planted last week, is like a large, shallow potted plant. It lies on top of two synthetic liners. A spongy mesh filters water before allowing it to pass on down to a thick rubber membrane, which keeps the building dry by directing the filtered water to a conventional gutter system.

The plants grow in 3 inches of light weight soil and crushed shale specially engineered to absorb as much water as possible. The plants consist almost entirely of a hardy species of ground cover called sedum, which forms a dense root structure but grows only a few inches high.

There are a few other plants mixed in with the sedum, including chives, which will sprout a purple flower in March to make the roof a little more interesting visually. Other varieties will produce other colors during the warm weather, according to Angie Durhman, who works for the Maryland-based roofing company, Magco Inc. , that is installing the green roof.

``It's not going to be a green roof per se; there's going to be a lot of diversity up there," she said. ``The flowers will just kind of pop up. It will be like a typical meadow."

About six green roofs have been installed in Massachusetts, Durhman said, including at the World Trade Center in South Boston, the Ikea store in Stoughton, and Boston City Hall.

In Ipswich, it will take the slow-growing sedum until spring to fill in completely. After that, it won't require much tending, Durhman said. Piping for a hose was extended to the roof for extreme drought conditions, and sedum is an alpine species chosen specifically to weather New England winters.

``You're still going to have to come up here and make sure the gutters are clean," she said. ``But you have to do that with any roof."

The state Department of Conservation and Recreation is sponsoring the green roof project as part of an effort to help the troubled Ipswich River, according to Sara Cohen, a water resources specialist with the agency.

The Ipswich snakes through some heavily developed areas, fed by rainwater that all too often travels across asphalt pavement or roof shingles, often picking up pollutants along the way, Cohen said.

Once the building is finished, the US Geological Survey will compare the water that runs off the green roof with run off from other buildings, Cohen said.

``We found the ideal location in this building; it's right next to a river," she said. ``These roofs provide a lot of very significant benefits where storm-water runoff is a problem, not to mention reducing building heating and cooling costs and preserving the life of the roof."

While the installation comes with a 20-year warranty, it is expected that the green roof could last up to 50 years, Durhman said. Green roofs are a novelty in this country, Durhman said, but they have outlasted conventional roofs in Europe, where they are more common.

All those selling points made it hard for the North Shore Housing Trust to say no to the project, Savoie said.

``Once we knew it was a benefit to the building and the environment, then there really weren't any negatives," he said. ``And the fact it's being done on an affordable housing project makes it all the more interesting. It's good to know that's it's not just for expensive projects."

It's also not the kind of roof the average resident is going to slap on top of the family home when the shingles give way, Durhman said. The weight alone makes green roofs useful only under certain conditions.

The roof adds about 20 pounds to each square foot of roof surface. State building codes also require any roof to be able to handle 30 pounds per square foot of snowpack on top of them.

The circa-1850 Annex building was strong enough to take the added weight, Durhman said. But without some kind of reinforcement, green roofs are out of reach of most existing houses and homeowners, Durhman said.

``It's hard to do it on a single-family home because of the costs to retrofit it onto an existing home. This is not for do-it-yourselfers."