The Role of Extensive Green Roofs in Sustainable Development

Abstract

<jats:p>As forests, agricultural fields, and suburban and urban lands are replaced with impervious surfaces resulting from development, the necessity to recover green space is becoming increasingly critical to maintain environmental quality. Vegetated or green roofs are one potential remedy for this problem. Establishing plant material on rooftops provides numerous ecological and economic benefits, including stormwater management, energy conservation, mitigation of the urban heat island effect, and increased longevity of roofing membranes, as well as providing a more aesthetically pleasing environment in which to work and live. Furthermore, the construction and maintenance of green roofs provide business opportunities for nurseries, landscape contractors, irrigation specialists, and other green industry members while addressing the issues of environmental stewardship. This paper is a review of current knowledge regarding the benefits of green roofs, plant selection and culture, and barriers to their acceptance in the United States. Because of building weight restrictions and costs, shallow-substrate extensive roofs are much more common than deeper intensive roofs. Therefore, the focus of this review is primarily on extensive green roofs.</jats:p>

Green roofs are not created equal: the hydrologic and thermal performance of six different extensive green roofs and reflective and non-reflective roofs in a sub-tropical climate

“…During small (<10 mm) rain events the green roofs were able to retain most if not all runoff similar to that found by Bengtsson and Villarreal (2005) for a roof with 40 mm of substrate, and by Macmillan (2004) with a substrate depth of 140 mm, but better than that in other studies (Teemusk and Mander 2007). Rain events greater than 10 mm this resulted in a range of responses in line with similar studies elsewhere depending on green roof type (Getter and Rowe 2006;Seters et al 2007), except that in this study, total runoff from some green roof types was not significantly different from the conventional roofs. Retention could be attributed to several mechanisms.…”

“…Although the building and environmental benefits of green roofs in temperate systems have been documented in several countries (Kohler et al 2002;Liu and Minor 2005;Getter and Rowe 2006), the investigation of similar benefits in other ecosystems have been somewhat neglected. In warmer, non-temperate systems where there are greater climatic extremes (e.g.…”

Media depth influences Sedum green roof establishment

“…as providing a more aesthetically pleasing environment to work and live (Liesecke 1998;Liu and Minor 2005;Meng and Hu 2005;VanWoert et al 2005a;Villarreal and Bengtsson 2005;Getter and Rowe 2006;Simmons and Gardiner 2007). By placing plants on rooftops, the vegetated footprint that was previously destroyed during building construction is at least partially replaced.…”

“…green roofs must exhibit characteristics such as easy propagation, rapid establishment, and high groundcover density (White and Snodgrass 2003;ASTM 2006;Getter and Rowe 2006). Low growing plants that spread and cover the substrate in a short period of time reduce potential erosion problems, inhibit weeds, and provide improved aesthetics.…”

Salt tolerance of common green roof and green wall plants

“…The impact of saline spray from roadways has not yet been documented, and would require more site specific information about the proximity of the roof to major roadways and the height salt spray achieves when leaving the roadway. Green roofs experiencing salt stress would likely not provide the optimal level of benefits usually associated with green roofs, such as stormwater retention, energy savings, reductions in Urban Heat Island, and carbon sequestration (Alexandri and Jones 2008;Getter and Rowe 2006;Getter et al , 2009Sailor 2008;VanWoert et al 2005;Wong et al 2007).…”