Green roofs in North America have been booming of late: last week, the green roof industry association Green Roofs for Healthy Cities, announced the results of a survey of its members finding that more than 3.1 million square feet of green roofs were installed in 2008, a 35 percent growth over the previous year.

At the same time, the city of Toronto -- not coincidentally the home base for GRHC -- adopted a mandatory green roof law yesterday, requiring 50 percent of the area of all new roofs be covered with greenery.

The GRHC's surveys indicated that the city of Chicago, Ill., which has long been a stronghold of green roofs, constructed the most overall square feet of green roofs in 2008, with over 548,000 square feet installed. See below for the full rankings:



Toronto's new mandatory roof law covers all new construction, requiring up to 50 percent green roof coverage on multi-unit residential dwellings over six storeys tall, as well as schools, non-profit housing, and commercial and industrial buildings. Larger-scale residential projects will be required to have anywhere from 20 to 50 percent of the roof area covered with a green roof.

"The City of Toronto's leadership on all things green took another major step by making it obligatory to have green roofs for all types of new buildings..." said Toronto Deputy Mayor Joe Pantalone, the primary champion of the new by-law. "This bylaw is a major part of the solution to climate change, the creation of green jobs and it represents a whole new mindset on how our cities approach the 20 per cent or so of surface area that are roofs." he added.

More details about the green roof law, as well as the growth of green roofs in North America, is online at GreenRoofs.org.

Toronto green roof photo CC-licensed by Flickr user 416style.