Green Roofs: Many energy efficient technologies are labeled "green" for their apparent environmental friendliness. Green roofs are the real thing – a rooftop layer of living plants over a waterproofing membrane. The greenery keeps a rooftop cool on a hot summer day, which trims home energy use and cuts down the urban heat island effect. The roofs also reduce stormwater runoff and extend roof life.

Most green roofs have two to four inches of topsoil planted with hardy plants. The added weight makes a green roof best suited for new construction, though retrofits are possible on a re-enforced structure. Up-front costs are about four times higher than a conventional roof, though the price may come down as green roofs gain popularity and contractors fill the demand.

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