Extensive Green Roofs
Extensive green roofs, or roof meadows, are lighter weight, less expensive, and require less maintenance than intensive systems.
Plants for extensive green roofs require only a few inches of growing medium (2.5 to 6 inches) and little additional irrigation beyond rain. They require minimal maintenance - checking roof drains, scanning for invasive weeds or seedlings - about the same level of attention required by a conventional roof. Typically, roof meadows are composed of plants like sedums, grasses, and wildflowers - plants that can thrive in a rooftop environment with limited water, shallow roots, and sparse nutrients.
A citywide infrastructure of green roofs will likely be composed primarily of roof meadows; they are more feasible for a large number of existing and new buildings in the city since they are less likely to require structural enhancement of the underlying roof.
