This week, San Francisco became the first U.S. city to require that certain new buildings be built with a green roof —an eco-friendly design technique that sows plants above a roofline. This latest action builds on a growing trend that has taken root around the world, and which boosters say offers significant benefits for the planet.
The new law, going into effect in January, will require between 15 to 30 percent of roof space on most new construction projects to incorporate solar, green roofs, or a blend of both.
The ordinance builds on an earlier bill passed by the city’s Board of Supervisors in April that requires new residential and commercial buildings 10 stories or shorter to install solar panels or a solar heating system that covers 15 percent of the roof.
“I think a lot of people have always wondered why we haven’t better used our roofs, » said San Francisco Supervisor Scott Weiner, who introduced both bills.
Some of the city’s developers have supported the new green roof law, saying they are glad it offers an additional alternative to meet eco-friendly requirements. Green roofs are cheaper to install than solar panels.
The EPA estimates green roofs start at about $10 per square foot for simple projects, or up to $25 per square foot for more ambitious designs (although they can also save building occupants money down the line).
Green roof legislation is being passed around the world. Cordoba became the first city in Argentina to require green roofs in July. France’s new legislation mandates at least partial coverage of green roof or solar technology on all new construction and goes into effect next March. In 2009, Toronto mandated green roofs on industrial and residential buildings. Germany’s green roof industry has been legislated and supported by the government in various ways since the 1970s.
Green roofs reduce stormwater runoff, improve air quality, and help mitigate the urban heat island effect. For building tenants and owners, green roofs reduce the need for heating and cooling. They also can provide food and a recreational area for residents.
Combining solar panels and green roofs can actually make each component work better. Solar panels can provide shade for plants and grasses, reducing the need for watering, while the panels work best when they are cool (green roofs can help lower temperatures compared to conventional ones).
“There is a win-win between solar and green roofs, » said Steven Peck, the founder and president of Green Roofs for Healthy Cities.
Source: National Geographic
