A traditional sod green roof at the Norwegian Museum of Cultural History.
An extensive green roof in Washington, DC
What is a Green Roof?
A green roof is any roof of a building or structure covered or partially covered with vegetation. Other names for green roofs include: eco-roof, nature roof, vegetated roof covers, and living roofs.
Green roofs have a long history dating back to the Hanging Gardens of Babylon and traditional sod roofs used on Scandinavia houses. Germany currently leads the world in green roof technology.
Many cities around the world are adopting green roof technology. Green roofs are increasing in popularity in the U.S. The best example in the U.S. is the City of Chicago that has mandated that all buildings funded by the city have green roofs.
Green roofs are ideal places to use water-wise plants. Conditions on rooftops tend to be harsh. High light intensity, windy conditions, high temperatures, and drought stress increase the need for hardy plants.
Recycled culinary water and rain water can also reduce the need for supplemental irrigation water.
Benefits of Green Roofs
Urban areas can benefit from green roofs in a variety of ways. Green roofs can significantly reduce the effects of heat on a building(s) and can also reduce the amount of storm-water runoff created from impervious rooftop surfaces.
Green roofs can also provide much needed urban outdoor gathering spaces and create appealing views from surrounding buildings.
Additional Benefits of Green Roofs
- Improve the quality of storm-water runoff
- Reduce the urban heat island effect
- Filter air pollution
- Increase habitat for birds, insects, and other invertebrates
- Reduce heating and cooling costs of buildings by providing increased insulation
- Reduce cost of roof maintenance
- Increase the lifespan of a roof
- Expand opportunities for urban agriculture
- Improve visual appeal
Types of Green Roofs
New technology and materials allow an elaborate system of layers to provide structural support, roof barriers, drainage, and planting media that supports plant life on the roof. Intensive and extensive green roofs are two types of green roofs in use today. Keep in mind that green roofs are difficult to construct successfully and should be installed with professional guidance.