Wednesday, September 30, 2015

Living Green in the Southwest: Green Roofs?

Tempe Transportation Center
Just after I posted on Monday that white roofs really do work, Marshall Carter-Tripp sent me two links to news articles about "green roofs". Googling I quickly learned that there is a as well as a, the latter I just began following on Twitter.

Ecosystem Gardening touts these benefits:

  1. They last up to twice as long as traditional roofs
  2. They slow the progression of rain into the stormwater system
  3. They mitigate urban heat island effects
  4. They provide an insulating layer to buildings, keeping them warmer in winter and cooler in summer, which decreases costs related to heating and cooling
  5. The vegetation absorbs carbon dioxide and produces oxygen
  6. They create habitats for wildlife
Of course, I'm concerned about the effectiveness of a green roof in our desert environment and the issue of water conservation. has this to day:

In desert communities, greenroofs can greatly enhance the residents' life quality due to their benefits:

  1. greenroofs provide thermal insulation, so as to reduce cooling loads (and avoid a few of the downsides of heavy AC use, like Legionnaire's disease and thermophilic actinomycetes)
  2. greenroofs provide acoustic insulation,
  3. greenroofs reduce heat island effect,
  4. greenroofs create wildlife habitat,
  5. greenroofs absorb occurring rain water, saving drains from intermittent overloading,
  6. greenroofs clean ambient air by absorbing CO2 and producing oxygen,
  7. greenroofs increase the roof lifespan.
Scientific American writer, Katie Moisse, puts forth in Over the Top: Data Show "Green" Roofs Could Cool Urban Heat Islands and Boost Water Conservation that a green roof is no more expensive than a white roof and conserves water at the same time.

I'm skeptical. Green roofs must take more work. I paint my roof white and I'm done. I have a green roof and I have another garden. (There are examples of green on a sloped roof and not just flat or stepped roofs.) I could use water from my evaporative cooler to water the garden. But how much trouble will it be?

There are examples of public places such as overpasses that function as neighborhood gardens. There are even studies such as those at ASU in Tempe, Arizona that are studying the viability and effectiveness of green roofs in our climate. The most ambitious is the Tempe Transportation Center Roof. The Water Resources Research Center of the University of Arizona discussed that Center's roof and touts similar benefits to those mentioned above. By the way the Tempe Transportation Center has an LEED platinum rating.

Certainly green roofs have a place in the built environment. Retrofitting a house may be too expensive BUT designing new homes to have green roofs is a real possiblility.

This is a subject to be re-visited for sure.

COMING SOON: elpasopolitcally

1 comment:

  1. YES! If done mindfully and correctly, i.e. using native drought resilient grasses, you'd hardly need to water them at all. Plus, you would be providing habitats for birds. I think it's a wonderful idea. But yes, painting the roof white is a much simpler approach. Still, I think it would be beautiful to see living roofs throughout El Paso.