Toronto's green roofs mandate: the right approach?

In May, Toronto became the first city in North America to enact a green roof mandate: “…any new development with floorspace of more than 2,000 square meters devote between 20 and 60 percent of its roof to vegetation.” A centuries-old technology, green roofs provide a wide range of benefits, including

  • Energy savings: the insulating factor of a green roof can reduce heating and cooling costs — a study by Environment Canada found 25% summer cooling savings in certain cases.

  • Reduced maintenance: green roofs can last twice as long as conventional roofs

  • Aesthetic appeal: Grass and plants are certainly much more attractive than standard roofing material — they can even provide a “getaway” space for building residents.

So why are developers in Toronto upset about the new law? As you might imagine, green roofs can come at a premium: Toronto developer Stephen Upton argue that the new mandate could add $200,000 (Canadian) to the cost of a new building.

While you could argue with Upton’s numbers, you may also wonder if a mandate is the way to go… especially in a down economy. Green roof installations are growing at a healthy pace in other parts of North America (35% from 2007 to 2008 in the US), and cities seeing the fastest growth are using more nuanced combinations of financial incentives and regulatory reform. It would seem such an approach is paying off: according to Green Roofs for Healthy Cities’ 2008 Industry Survey, the cities providing incentives, including Chicago, New York, Washington, DC, and Philadelphia, are also seeing growth in green roof installation.

We’ll have to keep an eye on Toronto; in the meantime, what do you think? Are mandates necessary and/or desirable? Are incentives preferable? Is there some combination of the two that can best prod developers into adopting green roofs as a building standard?

via MNN

Image credit: 416style at Flickr under a Creative Commons license