The Benefits of Green Roofs

Benefits

Green roofs provide a host of health and economic benefits for the homeowner, the community and the environment:

• Reduced heating and cooling costs. A green roof acts as a superinsulator, enabling the home to hold in more heat during the winter and keep out the heat during the summer. German studies show that green roofs help a home retain up to 50 percent of the heat typically lost to convection. A Canadian study found that a green roof reduces the average daily energy demand for air conditioning by up to 75 percent in the spring and summer.
• Extended life of roofing materials. The soil mixture and the plants protect the waterproof membrane and decking from sunlight and temperature extremes more effectively than conventional shingles, tiles or shakes. This enables the roofing substrates to last longer—on average two to three times longer—than those made with conventional materials.
• Reduced noise-pollution impact. The plant materials and soil mixture of a green roof absorb and deflect noise outside the home.
• Beauty and biodiversity. Green roofs are simply more beautiful to look at than conventional roofs, and intensive green roofs provide additional outdoor living space for homeowners. Green roofs also fill a void left by home construction, providing food and shelter for native birds and insects, which is especially important in urban and suburban areas.
• Diminished rainwater runoff. A green roof acts like a sponge during rainstorms, absorbing about 40 percent of the rainwater. The plants, soil and root system then filter out many of the pollutants the rainwater has pulled from the air, making the eventual runoff much cleaner. Further, green roofs delay the flow of rainwater into the municipal sewer system by about 45 minutes, which helps overburdened sewer systems cope with sometimes-large amounts of rainwater.
• Less carbon dioxide and more oxygen in the air. More plants equal cleaner air because plants actually collect carbon dioxide from the air and, as a byproduct of photosynthesis, replenish the air with oxygen. The plants on a residential green roof produce more oxygen than a typical family uses in a year.
• Diminished "urban heat island effect." The urban (and suburban) heat island effect is the increase in temperature in developed areas that results from removing vegetation to build hardscapes such as homes, shops and parking lots. The temperature increase elevates smog levels, exacerbates medical problems associated with heat stress and increases energy demand for cooling.