BRUNSWICK, Maine — In the world of energy sustainability, “green” is the buzzword: green energy, green cars, green buildings. When it comes to a new “green roof” installed recently at Bowdoin College, green refers to both form and function.

The roof is made of plants.

In addition to their visual appeal, the plants insulate the building from the blazing sun, absorb water that would otherwise become harmful run-off and will extend the life of the roof, according to John Simoneau, the college’s capital projects manager. The roof over the college’s boiler plant had to be removed anyway so a crane could install a steam-powered electricity generator in August, which represented another facet of Bowdoin’s goal of making its campus carbon-neutral by 2020. The generator will produce 10 percent of Bowdoin’s annual electricity usage.

“We thought it would be good to try a green roof,” said Catherine Longley, Bowdoin’s treasurer and senior vice president for finance and administration. “We thought this would be a good pilot to see how a green roof works in Maine.”

A green or vegetated roof typically consists of a normal flat roof with containers of plants growing on top of it. They have been gaining popularity in Europe for the past 40 years and today there are more than 100,000 acres of green roofs on that continent, according to the website of a Connecticut company called Green Grid, which provided the plant material for Bowdoin College.

Though the plants installed this week at Bowdoin College are from the sedum and chive varieties, Longley said they won’t show up in the college’s cafeterias. The plants were chosen because of their hardiness and the fact they will grow back year after year.

“Like any garden, we might have to cut it back every few years so it doesn’t get out of control,” said Longley.

The project was designed by Richard Renner Architects of Portland.

Renner said green roofs are slowly becoming more common in Maine and that he has incorporated them into several designs — including atop his own building in Portland, which he installed four years ago.

“Other than water it a little when it was first planted, we’ve done almost nothing to it,” said Renner. “We recently had to do a little weeding to remove some invasive plants, but we’ve been really impressed how robust it is.”

In addition to the green roof’s ability to deflect heat — as opposed to a flat, black roof’s tendency to absorb it — Renner said the way it looks is no small part of its benefit. At Bowdoin, the boiler plant’s roof is visible from the upper floors of the nearby Buck Center. Renner said green roofs also help alleviate storm water runoff, which is a serious environmental problem in densely populated areas.

“If all roofs were like this, it could make a huge difference,” said Renner. “The aesthetic and environmental issues add up to be a compelling reason to do this. It’s really wonderful to look at a green roof instead of a black waterproof membrane.”

Bowdoin College announced in 2009 its intention to become carbon-neutral by 2020. Longley said several campus buildings have been upgraded since then and that the boiler, electrical generation turbine and green roof are important steps toward the college’s goal. The overall project was bolstered by a $400,000 grant from Efficiency Maine.

Longley said Bowdoin College President Barry Mills was scheduled to announce new initiatives in the carbon-neutrality project on Friday.

Christopher Cousins

Christopher Cousins has worked as a journalist in Maine for more than 15 years and covered state government for numerous media organizations before joining the Bangor Daily News in 2009.