Do Green Roofs Really Reduce Urban Temperatures? What Don’t We Know?

[Rob Halpern]

It is fascinating when tech gets so trendy that it grows faster than the science behind it.

http://www.nature.com/news/how-cities-can-beat-the-heat-1.18228?WT.mc_id=TWT_NatureNews

[Eric Gilbey]

Rob, Great question…if you have not already become aware of the Landscape Architecture Foundation’s online resource called Landscape Performance Series, you may get the answers for which you are looking.

http://landscapeperformance.org/browse?keys=&benefits[0]=118&benefits[1]=121

So much more than just green roofs too…check it out.

[Rob Halpern]

Thanks Eric! That should be fascinating browsing and reading

[Trace One]

I thought green roofs were more about recycling stormwater, rather than reducing temps..i think there is no argument the the green roof affect on temps is negligable… link from previous poster very interesting…worth checking out..

[Rob Halpern]

In fact, even the claims about reducing storm run off are only true for intensive green roofs, not extensive ones. And extensive green roofs are far more common

[Andrew Garulay, RLA]

I’m always amused by the current skittishness our profession has regarding aesthetics. Why is it a sin to value aesthetics? I might be alone on this, although I sincerely hope not, but I believe that the aesthetic qualities of a roof top garden in an urban area has values that far out weigh whether or not they have a significant benefit to the ecosystem.

Why are we so compelled to market these improvements to people’s lives based on real or perceived ecological benefits when anyone can much more easily see and experience the human benefit? It is like introducing Miss September to a teenage boy and trying to convince him that a relationship with her would be really good because she could help with his home work.

It would make sense to me that a rooftop garden that people are enjoying will not be dismantled if it is found to have no ecological benefit. It makes just as much sense that one that is not being enjoyed for aesthetic qualities will not be maintained for very long even if it does have ecologic value – if it saves money it adds a third dynamic.

Apply the same values to the ecosystem as you would any other landscape architecture project and at the very least there is no adverse affect. It is really hard to believe that there are not at least subtle benefits from added habitat no matter how limited or isolated.

Are they everything that those who tout them say they are? Probably not, but what is?

[Alma Hernandez]

[Alma Hernandez]

Its really interesting that green roofs reducing on 0.5 degree of air temperature in a day but also reducing energy costs because it acts as an insulator in summer season.

See, nature has the key to balance the everything even temperature. If we use natural resources then off course our efforts can reduce the affects of green house gases.

[Andrew Garulay, RLA]

Apply the same ecologic values to a roof top as you would to any other project. There are different opportunities in a roof top, but our values should be consistent.

I hope that clears things up.

Thanks

[Rob Halpern]

To be clear: the issue is not whether green roofs are pretty, sometimes provide habitat, sometimes reduce run-off, etc.

The issue, IMO, is when we promote the equivalent of a cup of tea to cure baldness and cancer. It’s a nice cup of tea. That’s all. There are green roof designs that do some real good for the environment. Let’s find out what those approaches are and be clear when we are not using them to speak truthfully about the benefits of the design at hand.

Telling our clients and ourselves that we have made the city sustainable without any supporting evidence is not going to make things better. We cheat ourselves and our clients if we speak forcefully from ignorance.

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