While there are many standards by which to measure green building, the United States Green Building Council (USGBC) has created the comprehensive Leadership in Energy and Environmental Design (LEED) program to guide individuals, organizations, and developers in building better communities.
Incorporating green roofs into a building can lead to up to 14 LEED points. Here are some that may apply.
Stormwater Management: SS Credit 6 – Green roofs may reduce stormwater discharge by more than 25% (rate and quantity). Green roofs may also be considered as stormwater treatment through their ability to remove suspended solids and other pollutants. Potential Points: 1 point
Heat Island Reduction
Roof – SS Credit 7.2 – Green roofs can reduce roof temperatures from summertime highs of up to 180°F to less than 80°F, especially in cities. The USGBC specifies green roofs as a way to meet this objective, when the green roof installation covers at least 50% of the roof surface. Potential Points: 1 point
Water Efficient Landscaping – WE Credit 3.1-3.3 – Green roofs can be designed so that irrigation is not required. Drought-resistant plants can be selected or greywater systems can be directed onto the roof to irrigate. As an added benefit, runoff from the green roof is filtered by the vegetation and soil media, so this water can be used to irrigate other landscaping features without pretreatment. Potential Points: 1 to 3 points
Energy and Atmosphere
Optimize Energy Performance – EA Credit 1 – Because of their heat absorption properties, green roofs have been shown to reduce energy demand by more than 50% annually in certain types of structures, geography and configurations. Reduced demand and increased efficiency may also lead to smaller cooling systems and lower capital costs. Potential Points: 1 to 15 points, depending on total energy reduction levels and other factors.
Innovation and Design Process
Green roofs may qualify for innovation and design credits by improving the workplace environment, creating an educational laboratory, or a recreational space. Potential Points: 1 point
(Source: Green Buildings.com)