Green roofs redux

Post by Eric Mang in

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Green roof: benefits worth the cost?

Last week, I got a little heated over so-called “climate change deniers”. I should have included a reference for the one or two silly people out there who claim there is not scientific consensus (a lesson in always backing up an assertion with evidence).

Going back to 2004, an editorial in Science magazine noted that most noteworthy (read: not purveyors of junk thought) scientific organizations agree with the evidence for anthropogenic climate change. And between 1993 and 2003, of 928 abstracts discussing some element of climate change, none disagreed with the consensus position.

So let’s move on…

In the same post last week, I lauded those cities who have embraced green roofs. Vancouver, you sexy urban beast, you recognize that not only does it bring all sorts of environmental benefits, some reap delicious rewards with rooftop gardens. Furthering BC’s green leadership, Port Coquitlam is the only municipality in Canada that requires green roofs on new builds.

I also noted that whenever Chicago does something grand, its sister city Toronto likes to follow. Chicago is a North American leader in green roofs. And Toronto’s Planning and Growth Management Committee (P&GM) is recommending that green roofs must be mandatory on buildings with big footprints starting January 31, 2010 (this process started in 2006 and has included extensive consultation.)

Naturally, not everyone is happy and I think I can see why.

On March 27, 2009, specifics were laid out for green roof coverage depending on building footprint. If the building is 5,000 to 9,999 m2, 30% of the roof must be greened. As the gross floor area increases, so does the demanded coverage. At 20,000 m2 or greater, 60% of the roof must be verdant. (There is discussion to lower the minimum footprint threshold to 2,000 m2 with a minimum coverage of 20%)

But the exemptions have some bristling.

The draft by-law (section not specified yet), exempts residential buildings under 23 metres in height (that height has been revised to 20 metres), schools, non-profit housing and, here’s the source of irritation, industrial buildings (see page 7).

Indeed, in a committee supplementary report dated April 22, 2009, the P&GM Committee stated that industrial buildings should be exempt:

“This was in keeping with City Council approved polices in place to protect and encourage employment uses within the city, including policies in the Official Plan, a city-wide financial incentive program for key employment sectors.”

The Committee tried to bargain with industrial developers by providing “a maximum green roof area of no larger than 10 percent of available roof space up to a maximum size of 2,000 m2

Nay, said the developers. This would still cost us about $200,000 for big buildings. So decided yesterday, green roofs for industrial buildings have been deferred until 2011 and then a meager 10% of the roof must be green. (Exemptions for schools and affordable housing have also been removed)

A condo developer is baffled as to why the city is considering letting big industrial buildings essentially off the green roof hook. But the city proclaims, “we don’t want to scare off jobs”.

Sounds like a feeble defense (and is there evidence that requiring builders to spend $10 to $40 per square foot to install a green roof will drive builders away? If there is, we should see it). Not only are there significant environmental benefits (and energy savings) as evidenced in cities around the world, some, such as the Fairmont Waterfront in Vancouver, harvest fruits, vegetables, herbs and honey (yes, I know Toronto’s climate is nothing like the balmy Wet Coast, but that doesn’t mean we can’t grow some tasty tomatoes for part of the year).

City Council has yet to vote on this before we see anything happen. Let’s hope Mayor Miller and City Council take a page out of Chicago Mayor Daley’s enviro-book and make new rooftops in TO substantially green - even for new industrial buildings.

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