A green roof is a conventional roof that is covered with a layer of vegetation. Also known as “living roofs,” green roofs serve several purposes for a building, such as absorbing rainwater, providing insulation, creating a habitat for wildlife, and helping to lower urban air temperatures and combat the heat island effect
. There are two types of green roofs: intensive roofs, which are thicker and can support a wider variety of plants but are heavier and require more maintenance, and extensive roofs, which are covered in a light layer of vegetation and are lighter than an intensive green roof.
Green roofs are versatile for all building types that have a flat or low-slope roof that can support the weight of the vegetation and its support system. Important factors to consider when building a green roof are the drainage system, sun and wind exposure, and the types of plants for your climate, which can be recommended by a local landscape architect. There are potential concerns and drawbacks to installing a green roof, including the difficulty of repairing leaks, relatively new (though well-proven) technology, competition with other roof functions such as solar panels, and installation costs. An extensive green roof may cost $12 to $24 per square foot, although less expensive alternatives are available.