Green Roofs = Good Idea Too

"Construction of green roofs grew 30 percent in North America last year," reports the Chicago Tribune.

White roofs, green roofs, what can I say? My grandfather was a roofer.

The architects and engineers have done a lot with green roofs here at UVA, especially as part of their ecoMOD project (noted in earlier posts). I've had the fortune to advise a few undergrad projects on this and, in great part through those students, learn about the feasibility, benefits, and challenges of green roofs.

Here's the New York Times chiming in a few weeks ago: "Green Roofs Offer More Than Color for the Skyline." And here is the Chicago Tribune today, "Green roofs are taking root in American cities," discussing how other cities are trying to achieve the success Chicago has had.

Treehugger has an extensive list of posts on green roofs. They're always good for a link.

Among the benefits are these:

In general, green roofs cost about twice as much as standard ones but offer at least double the life span because they are less vulnerable to the wear and tear of temperature extremes (says The Tribune).

The Tribune reporter notes that this is why we've seen the most promising examples coming from communities and municipalities.

[G]reen roofs, which soak up and slowly release large amounts of rainwater, help prevent the storm runoff that causes water pollution in many cities with combined sewer overflow systems like New York's and Chicago's (Tribune)

Plus:

Temperatures on buildings with green roofs are up to 30 percent lower during the daytime in the summer than they are on those with conventional roofs, which means that tenants on the floors below do not have to run their air-conditioning as much. (NYT)

The Europeans have known this for some time and the Germans in particular have done well with it. Students in my class found that in 2001 alone, Germany constructed over 145 million square feet of green roofs, up from 97 million square feet built in 1994. If anyone has the figures for last year, I'm sure it'd help make a good chart.

Overall, then, the benefits range widely. As researchers at the University of Florida wrote in 2004, green roofs can reduce pollutant levels and storm water runoff, filter chemical air pollutants, moderate urban heat island effects, create wildlife habitats, and increase the thermal insulation of buildings (when not soaked with water), therefore reducing the cost of heating, cooling, maintenance, and replacement.

These are in the cost category of compact fluorescents: the higher upfront price is offset by long term life-cycle benefits. Along the way there are a host of environmental benefits.