The greening of North America

Green roof systems gain popularity as incentives are developed

The development of "green" buildings that regenerate degraded urban environments is essential to building healthy, sustainable communities in the 21st century. According to the U.S. Environmental Protection Agency and Lawrence Berkeley National Laboratories, Berkeley, Calif., rooftops represent 15 percent to 30 percent of the total land area in major cities. As such, they present a tremendous opportunity for positive change as a key component of green building and sustainable roof system design.

There are two basic types of green roof systems: extensive and intensive. Extensive green roof systems range from 1 inch to 5 inches (25 mm to 127 mm) in soil depth, typically consist of mosses and herbs, and are built primarily for their environmental and economic benefits rather than public access. Intensive green roof systems require at least 1 foot (0.3 m) of soil depth, elaborate irrigation and drainage systems, and maintenance. Typically designed to be publicly accessible, intensive green roof applications feature trees and shrubs and often resemble city parks.

The multiple paybacks of green roof systems are far-reaching and involve a mix of public and private benefits, including the following:

  • Storm water quantity improvements and related benefits to aquatic habitat, erosion control, flooding and water quality

  • Urban air-quality improvements, such as heat island reduction and reduced smog

  • Improved access to green space

  • Biodiversity preservation

  • Community gardens and urban agriculture

  • Horticultural therapy, which involves the active and passive interaction between humans and plants, resulting in improved mental and physical well-being for humans

  • Energy efficiency, particularly during summer

  • Increased roof membrane life

  • Noise abatement

  • Improved efficiency of photovoltaics

  • Reduction in radiation from telecommunication towers

  • Aesthetic benefits for building occupants and those in surrounding buildings

Give them a reason