Ecological impacts from impervious surfaces are not limited to parking lots and roadways. Roofing - whether it be shingles, metal sheets, or tile - adds up to a considerable amount of surface area, especially in urban settings. In addition to generating runoff which can lead to downstream erosion and exacerbate flooding, roofs contribute to the heat island effect by reflecting and radiating heat from sunlight back into the surrounding area, elevating ambient temperatures. This in turn results in higher energy expenditure on cooling which may contribute to carbon emissions, creating a vicious cycle.

While potentially costly, green roofs substantially reduce runoff and nearly elliminate the heat island effect of conventional roofing materials which can result in a cooler home during the summer. Green roofs usually are made from pre-grown trays that include a thin, sandy planting medium and a blend of hardy plants such as sedum, chives, and other grasses or forbs. Once established, these biological systems are both drought and cold hardy and long-lasting with appropriate weeding and maintenance.