Summer is just around the corner, and for those who live in big cities, that means spring warmth will soon give way to searing heat. Green roofs can help regulate city temperatures, giving people, and the electrical grid, a much needed break.
Toronto is the first city in North America with a bylaw that requires roofs to be green. And we're not talking about paint. A green roof, also known as a living roof, uses various hardy plants to create a barrier between the sun's rays and the tiles or shingles of the roof. The plants love the sun, and the building (and its inhabitants) enjoy more comfortable indoor temperatures as a result.
Toronto's new legislation will require all residential, commercial and institutional buildings over 2,000 square meters to have between 20 and 60 percent living roofs. Although it's been in place since early 2010, the bylaw will apply to new industrial development as of April 30, 2012. While this is the first city-wide mandate involving green roofs, Toronto's decision follow's in the footsteps of other cities, like Chicago and New York.
Under the direction of Mayor Richard Daley the city of Chicago put a 38,800 square foot green roof on a 12 story skyscraper in 2000. Twelve years later, that building now saves $5000 annually on utility bills, and Chicago boasts 7 million square feet of green roof space. New York has followed suit, and since planting a green roof on the Con Edison Learning Centre in Queens, the buildings managers have seen a 34 percent reduction of heat loss in winter, and reduced summer heat gain by 84 percent.
But lower utility bills aren't the only benefit of planting a living roof. In addition to cooling down the city, green roofs create cleaner air, cleaner water, and provide a peaceful oasis for people, birds and insects in an otherwise polluted, concrete and asphalt-covered environment.
Image via Flickr/pnwra
Follow Beth Buczynski on Twitter: 
Seriously good call. This is very precious space in a compact urban area, and it should be put to good use instead of just being restricted real-estate with a couple of dishes and a bunch of pigeons.
The green roof bylaw was actually enacted on January 31, 2010 by former Mayor David Miller. So far it has resulted in over 1,000,000 sq ft of green roof with another 1,600,000 sq ft in planning stages.
The key green roofs in the city to date are the Podium Green Roof at Nathan Phillips Square (accessible for anyone who want to go up there), two green roofs on Toronto Transit Authority stations and several on Police Stations. In addition every new condo has a green roof. There are only 160 of those in the process of being built. So while the former are 20-50,000 sq ft each in size, the latter are 5-10,000 sq ft. But there are a good number of them.
I don’t get it. If the benefits were as advertised, business savvy building owners would have done it long ago or on their own accord now. Instead, we will now have (for life) a government office of green roofs, wielding obnoxious moral authority to punish those whose plants cover 3% too little of their roof.
Beth, I’m so happy you wrote about this, but the Toronto Green Roof Bylaw was enacted mid-2009 and came into effect for condos, commerical, etc buildings over 2000 m2 in 2010. Industrial buildings over 2000 m2 were to be included at the end of april 2012, but the new Mayor Rob Ford put a moratorium on it – they will review after 15 months….They will probably kill it altogether (it is, after all, a David Miller (the former mayor) legacy project – and the Developers HATE having to spend any extra money they don’t “have to” – so does the Catholic School board.)
http://www.toronto.ca/greenroofs/overview.htm
So… if I don’t have a green roof what happens? I get fines, and if I don’t pay them I lose my property, and if I still don’t pay people with guns kidnap me and take me to jail? No thanks.
I’d prefer if the government spent time/money making it easier for people to create green roofs by providing documentation and coordination instead of anything punitive.
Anthropogenic global warming is a falsehood perpetuated by an embedded mainstream media. To mandate draconian, liberty-starving laws is an injustice based upon a falsehood. It is better to tell people the truth about life on our planet and why we are here and give people the liberty to choose their own destiny based on that truth than to mandate a fraud.
And the roof wont collapse over time what with the additional weight from soil, plants, trees and water and people walking around on it??????Even adding this to the roof of a building built in 1922?
It’s a great idea…but it does worry me……..
Thanks for pointing out the oversight Ashleigh. The dates have been corrected. Sorry to hear that the government might be rethinking the rule for new construction. It has the potential to do so much good, and set an example for other cities of the world.
Lots of ignorance about when it comes to green roofs even in the few comments here.
Large buildings in dense urban cores bring lots of stormwater issues that weren’t there before. Green roofs by themselves or in conjunction with controlled flow drains on roofs are a much cheaper and easier solution to control stormwater than sewers and water treatment plants. The latter the developer pays for in development charges to the city, the former he pays companies like mine for directly. As development density increases it is much cheaper for both the developer and the city to add green roofs than it is to increase the size of old sewers. The green roof, the controlled flow drains and any measures such as cisterns and rain gardens at ground level combine to control stormwater at source rather than at the end of the pipe. This approach is much more logical and much less expensive than the old fashion end of pipe approaches.
So while a green roof bylaw seems like an imposition of a draconian measure to some, it is in effect a winning proposition for both the developer and the city as it allows development of sites that would otherwise be off limits due to undersized stormwater infrastructure.
It should be noted that many developers are notoriously cheap. If it weren’t for the building code imposing the use of a minimal level of insulation in roofs and walls, many builders would be very tempted to simply skip that step. When minimal insulation standards came into effect, and subsequently were raised in each revision of the Ontario Building Code, there was opposition from builders even though the code was in their best business interests. They have learned to embrace the changes and actually appreciate the standard in the code so that everybody competes under the same standard. The same will be true for green roofs, when they become more widely accepted and understood opposition will die down and they will be applied voluntarily like they are all over the world from Norway and Germany to China and Malaysia.
As for the structural questions, have your building checked by an engineer before putting on a green roof