Study shows green roofs can help cool cities
Imagine grass covering the roofs of New York City’s public schools…
A study by scientists at Columbia University has confirmed that green roofs — roofs covered with growing plants —might be one of the best ways to cool cities in the century ahead.
Stuart Gaffin and his team of students at the Center for Climate Systems Research at Columbia used thermal imagery from satellites, and regional climate models, to study the urban heat island of New York City. It’s well known that cities are warmer than the surrounding countryside.
Stuart Gaffin: The last thing cities are going to need in the era of global warming is more heat from their own additional sources. We view it this way. By trying to mitigate urban heat we’ll be mitigating some of the impacts of global warming and we’ll be doing this for urban centers that will house more than half of the world’s population.
Gaffin and his students looked for ways to cool large cities.
Stuart Gaffin: The results vary. It depends on the borough, the available land area for conversion, and the scale on which it’s done.
They considered light–colored roofs and planting more trees. But these scientists think the most effective solution could be “green roofs:” roofs covered in vegetation.
Gaffin hopes green roofs can be installed on public school buildings, especially in lower income areas where there’s more pollution and fewer air–conditioners. Our thanks today to NASA :explore, discover, understanding. We’re Block and Byrd for Earth & Sky.
The urban heat island effect happens because pavement, tar, and other dark, impervious surfaces trap heat. When you add in car motors and ever–present construction, a city can heat up quickly into a potentially deadly heat wave.
Speaking of his 2006 study of the urban heat island effect and possible solutions, Dr. Gaffin said, “We can’t afford to rule out any one of the methods (for mitigating the urban heat island effect) because they have different strengths and weaknesses.”
He added, “We also want to see this more take place in the lower–income neighborhoods because that’s where there important environmental justice issues are. These are places that have low air–conditioning rates, high levels of air pollution. So that’s why we’re trying to work on public schools, especially low–income public schools.”
Green roofs are a good solution because – in addition to creating a cooling effect – they also help with another urban problem, that of conserving storm water runoff.
Our thanks to:
Dr. Stuart Gaffin
Center for Climate Systems Research
Columbia University
New York, NY
I would love to have information on how to convert the flat rooftop section of my home to a green space. Where should I look ?
Susan:
Try going to
Green roofs for healthy cities
http://www.greenroofs.net/index.php?option=com_content&task=view&id=26&Itemid=40
You have to go way to the bottom of the page—see “What do I need to know about my building before I initiate a green roof installation?”
Dear Susan,
A good first step might be to try and find someone in your area who has constructed a green roof. They might be able to give you advice about what will be needed to obtain the necessary city permits to make everything nice and legal.
Building a green space on a rooftop adds anywhere from 20-150 pounds per square feet (in addition to loading from snow), so you’ll need to prepare your roof to handle that. The City of Chicago recommends getting advice from a licensed structural engineer or architect to analyze what your roof is capable of. You can find out a little more of the nitty-gritty behind actually making that rooftop garden in a pamphlet distributed by the City of Chicago’s Department of the Environment, downloadable at this link for free.
Your municipality might have something like a Department of the Environment to give you information more specific to where you live. Good luck!