With temperatures in the 90s, air conditioning units in the region
have been working overtime. But it's possible the vast number of air
conditioners in urban areas, could be making summer in the city a
little hotter than in the suburbs. Brad Linder has more.
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Hot time in the city.
Cities are known as "Urban Heat Islands," yet solutions
to this problem may be as simple as planting more trees and painting
roofs white.
July 23, 2002
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By Dan Simon
As you heard in Brad's story, cities such as Philadelphia and Pittsburgh
are known as "heat islands," principally because they tend
to be hotter than their suburban neighbors.
Planting more trees and green space could help Philadelphia
and other cities stay cooler. Photo ©Dan Simon for GreenWorks
TV.
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It's not hard to see why cities are hotter. Take miles of black asphalt,
thousands of black tar paper roofs and thousands of large buildings
that soak up the sun's energy during the day, and then release it
back into the atmosphere into the night, and you have a recipe for
baked occupants. Brad's story about how building air conditioners
pump even more hot air into the atmosphere just adds one more reason
why cities can be as much as five to 10 degrees hotter than their
neighbors.
Researchers are proposing several ideas to help keep cities cooler.
Planting trees and grass and converting roofs to lighter, heat reflective
colors, can help make things cooler, plus make the city more attractive.
In June, Brad
reported on a group that was applying a white coating to selected
roofs to help keep their homes cooler. This program was geared to
helping individual residences though. No comprehensive program to
try to convert a large number of the city's row home roofs to lighter
colors is underway at this time, but early feedback shows the white
roofs effort is worth a further look.
Another approach has been suggested by landscape architects at Temple
University's Ambler campus, namely "green" roofs. The idea
is to use rooftop gardens to also help reduce city temperatures and
better control runoff from rainstorms.
There's an existing example of this idea at the Fencing Academy of
Philadelphia where a 3,000 square-foot roof garden has been in place
since the spring of 1998. The lush meadow-like garden only puts a
pressure of 15 pounds per square foot on the building's roof.
"It's been working very well," said building owner Mark
Masters. "I'm extremely pleased. I can't say how much it's reduced
my energy costs, but I do know my apartment looks out over the roof
of my fencing club.
"As soon as we installed it, I started using my air conditioning
less. The reflective heat was being absorbed by the ground cover.
We got that benefit immediately."
There's an added benefit in that the rooftop garden, which features
a mix of Sedum varieties, is just a nice place to hang out.
"We have a deck up there," Masters said. "In the evenings
we'll go up on the deck and relax. We have a dog and he likes to go
up there and play on it. You do have to be careful though. You can't
walk on it much. It's a shallow soil and walking on it would damage
it."
The shallow nature of the rooftop garden is important because it keeps
its weight down.
"They use some kind of membrane technology to retain moisture
underneath it while keeping it light," Masters said. "We
didn't put our roof up with the idea of doing this, it was a retrofit.
We're really happy to be on the cutting edge. I just consider myself
really lucky to have this."
Roofscapes Inc., the same company that designed the Fencing Academy's
green roof, also recently completed a project on the 14th floor of
the Heinz 57 Building in Pittsburgh. This effort created a green oasis
to work with the building's top floor penthouse.
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