Wednesday, May 27, 2009

Toronto Getting Green Roofs

From the U.K. Times On-line:

Steven Chu, the Nobel prize-winning physicist appointed by President Obama as Energy Secretary, wants to paint the world white. A global initiative to change the colour of roofs, roads and pavements so that they reflect more sunlight and heat could play a big part in containing global warming, he said yesterday.

From the new city by-law adopted just today:

The purpose of the Eco-Roof program is to provide incentives to commercial, industrial and institutional (ICI) property owners so that Toronto’s building stock becomes more sustainable and better adapted to climate change. The program is intended to complement the proposed Toronto Green Roof Bylaw and the Green Standard (formerly the “Toronto Green Development Standard”) by encouraging owners to take advantage of their roof space. An “eco-roof” would include green roofs that support vegetation and cool roofs that reflect the sun’s thermal energy.

One of the things Mayor David Miller has accomplished that doesn't suck.


John Mashey said...

This is good long-hanging fruit, although more so here in California than in Toronto, perhaps. Everything helps.

Here's the Rosenfeld 2-pager from last year, including a pointer to the real paper.

Here's some more discussion of albedo effects, over at RC.

The comments on the TimesOnline: amusing, sad.

Kurt Phillips said...

Interesting idea, though I'd be concerned that glare off of white roads could result inaccidents. Then again "white" might be simply a much lighter color than what is used currently and my concerns unfounded

BigCityGlib said...

Chu might have a lot of education but his knowledge o atmospheric physics is piss-poor.

Soon as incoming shortwave radiation form the sun hits something solid it gets converted to longer wave radiation heat in some form.

Whether or not it gets bounced back and warms the atmosphere directly or warms up a few miles of asphalt that gets warm and then cools off (gives up its heat) at night, the end result is the same.

John Mashey said...


Have no fear. I live in California, about an hour away from LBNL, where this was hatched. We already have rules in place, about to take effect.

You can easily get confused by a breathless press account based on a few words at a conference.
Read the real stuff, like that Rosenfeld 2-pager.

1) Nobody is painting roads white. They just want to raise the reflectance to make blacktop look more like concrete.

2) They want to paint flat roofs white. [Although solar panels are even better, but they don't apply everywhere.]

3) They want sloped roofs to use higher-reflective (colored) paints.

And of course, it matters where you are. It matters a great deal anywhere in the US Southwest, but if air conditioning costs more than heating, it's interesting. it obviously matters more in urban areas than rural ones.

perhaps you do not understand the meaning of albedo?

Chu certainly does.

Steve Bloom said...

Hmm, I think BigCityGlib just proved that mirrors can't exist.

BCL, the fact that at this late date prople are simply being "encouraged" to take such steps isn't what I would call good news. Espcially for things like reflective roofs that don't cost more than non-reflective ones, we need laws making them mandatory for both new construction and replacement roofs. IIRC the CA law doesn't even contemplate such a thing, which is a monument to the love that rich people have for their shake and tile roofs, and to the continuing triumph of the Efficient Markets Hypothesis over reality.