Planning and Building Cool Cities

Okay so far it's been the hottest year recorded in U.S. history, cities and utilities have been pushed to the breaking point, hundreds died in California, Chicago, New York and other U.S. locations from this summer's extreme heat. What's our best collective move--in addition to cutting carbon emissions--to cope with more of this in the future?

Lisa Gartland, of PositivEnergy in Oakland, CA, came by SustainLane yesterday to put things in perspective.  After admiring our 1904 building's passive cooling architecture: interior atrium, high ceilings, large operable windows and door transoms, she was eager to discuss why one would think that cool city development strategies should be inevitable.

"We have had urban warming for years through the heat island effect, and on top of that we have global climate change with likely associated heat waves," she said. "Add these together and you're really screwed. It's true and it's just awful."

Gartland's work with for one of the nation's hotter cities, Sacramento, California, has produced deeper insight into urban heat islands, which can raise temperatures more than 10 degrees higher than surrounding non-urbanized areas. A PhD, she is also author of the potboiler "Mitigating Urban Heat Island Effect" for the US EPA.

Chicago's 1995 heat wave, perhaps the first major urban harbinger of global warming,  is now estimated to have killed from 485 to more than 700 people.

"Because of that heat wave a lot of good things happened." Gartland said. For instance, since 2000, when Mayor Daley had a green roof put on top of City Call, the city has been undertaking a great urban experiment that one day may be hailed alongside Daniel Burnham's efforts of yore. Chicago now has 2.5 million square feet of green roofs, including the already-legendary installation at Millennium Park. The city also is a leader in offering cooling centers, providing transportation, and managing social networks to protect people.

"A lot of people that died during the 1995 heat wave were in the top floor of apartment buildings, facing west."  Her description continued, becoming more viscerally acute. "When it gets above skin temperature, about 95 or 96 degrees, if you start to blow air from a fan, you're cooking yourself instead of cooling off. Because the rooftops of buildings absorb heat, they can get from 180 to 200 degrees. That heat is being conducted through the roof and radiating on your body."

Okay I'm feeling uncomfortable now, even in breezy downtown San Francisco.

Gartland mapped hot spots in Sacramento in conjunction with a NASA flyover, and discovered that one of that metro region's highest infrared spikes was from a cluster of two- and three-story-high corporate office buildings, surrounded by blacktopped asphalt.

"That's what's happening in our suburbs--two- or three-story buildings surrounded by parking lots, with no real shading from the buildings."

Besides appropriate landscaping, including trees or vines on western and eastern exposures, Gartland advocates new roof technologies that can reflect 60 percent of heat from solar energy. These concrete-tiled roofs get up to 120 degrees, which doesn't noticeably impact interior comfort underneath a well-insulated rooftop. California's National Coatings is one company offering such products, she said.

Besides the cool roofing, open space is key to cool cities, as are energy-saving green roofs, and even traditional design features that have been lost to cost-cutting strip mall architecture: overhangs, awnings, transoms, attics, and windows that open.

Then there's the pavement that's covering more and more of urban areas. It's mostly black, made of asphalt (which causes water pollution through run-off), so it gets incredibly hot. Gartland recommends leaving sand out of both asphalt and concrete to make pavement more porous, which helps it filter water and evaporate moisture more like soil. She also says lighter-colored pigments such as grays, pinks and even white, can reduce heat absorption.

And she pointedly notes concrete is significantly lighter then asphalt in color.

Roofs comprise about 20 percent of urban area groundcover. So why not deploy cool roofs enmasse, saving business and residents energy? Gartland said that Lawrence Berkeley Laboratory estimates that 20 percent is also the estimated reduction in cooling costs for commercial cool roofs--residential energy savings might be even higher since people have to try and get some sleep under those hot roofs at night.

Infrastructure needs to be cooled off as well in our urban lands if we want to avoid a repeat of this summer's horrors. Parkland, strategic and well-managed tree planting and maintenance programs, lighter pavement, grass or permeable pavers--all of these seemingly little steps will add up, especially when part of city- or statewide programs. Philadelphia and Denver are two cities that have actively increased or plan to significantly increase their tree canopies.  Chicago has planted more than half a million trees since mayor Daley took office, in addition to greening roadway overpasses, median strips and boulevards with shrubs, grasses and flowers.

Besides more comfort, these steps offer real lifetime energy cost savings for all.  And perhaps most notable, they reduce the draw on our grid so that the power stays on when we really need it, when it's a matter of life and death.

Comments

[David]

Warren,

I happened to see an excellent documentary the other evening called "The End of Suburbia" which goes into detail about the constraints and strains on "the grid." When it gets hot, every little bit of energy saved counts! Attention to architectural features such as operable windows and overhangs make common sense. How about inviting the folks down at "Dwell" magazine over to the SustainLane offfices to initiate a dialogue with the trendy, increasingly green-oriented, design world....

[thebizofknowledge]

We only have to watch the evening weather forecast to learn that our cities are usually warmer than the surrounding areas. I've wondered for years why all those hot asphalt covered roofs are not being outfitted with solar panels, which would tremendously reduce our overall electrical consumption!

[Dr.S.Ramesh]

Its really an excellent thought and wisdom to make cities cool and comfortable with due considerations to the ecology & environment.

[Nathan Matlin]

I think its going to be a slow process, but a process that needs actioning immediately. Ideas like more canopies, less asphalt, and solar panels are all things that are very achievable by local governments and authorities, however I don't believe there is nearly enough being done about it. Nice post Warren