WAMU 88.5 : Metro Connection

How Hot Are D.C.'s 'Heat Islands'?

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Brendan Shane, director of policy for the District's Department of the Environment, on his "cool" roof.
Jonathan Wilson/WAMU
Brendan Shane, director of policy for the District's Department of the Environment, on his "cool" roof.

Kurt Shickman stands near the corner of 9th Street and Barry Place in Northwest D.C. He’s focusing on two pieces of posterboard — one black, one white — he’s laid on the grass next to the sidewalk, and is holding what looks like a grey and yellow radar gun in his hands.

“So this is just an infrared camera, and it looks at both temperature and the thermal imagery of various objects,” he explains. “It gives us a really good, accurate reading on temperature.”

It might just be the hottest day of the summer, at least thus far. It’s about 93 degrees out.

The two pieces of posterboard have been lying in the sun for ten minutes or so – and it’s obvious the black one will be hotter, but just how much hotter?

“So you can see here on the left, the black piece of paper is about 156-160 degrees [Fahrenheit],” Shickman says. “And we'll just scan over to the white — and it’s about 93-94 degrees, which is about ambient temperature — that’s about how hot it is right now.”

That is, for the record, about a 65 degree difference.

It’s a simple, yet brutal demonstration of why cities—– chock full of black roofs and black streets — are hotter than their more rural surroundings a phenomenon known as the heat island effect.

Kurt Shickman, Executive Director of the Global Cool Cities Alliance. (Jonathan Wilson/WAMU)

Hotter than average

Kurt Shickman knows a lot about heat islands. It’s his job as executive director of the non-profit Global Cool Cities Alliance, an organization dedicated to helping cities mitigate heat island effects.

“The way we have built cities in the Mid-Atlantic and the Northeast – they tend to have some of the worst heat islands in the country,” he says.

D.C.’s heat island effect often makes it close to 10 degrees warmer than surrounding areas. Shickman says the average heat island is 5-8 degrees warmer. In other words, D.C. is pretty good at turning hot summer days into sweltering ones.

But D.C. is also a hotbed of heat island research. City leaders are currently working with scientists at the University of Michigan to get a more exact picture of which neighborhoods suffer the most when the mercury rises, and exactly how many new trees and white roofs it would take to make a difference.

Shickman says this neighborhood, along 9th Street in Northwest, provides a good example of an area that could use a cool-down.

“If you look on the west side of the street, you get an example of what not to do. There’s no trees on that side of the street, just a lot of concrete — a lot of asphalt,” Shickman says, surveying a large, fenced in parking lot.

A lighter shade of cool

The city is not going to eliminate blacktop parking lots anytime soon, but District leaders are pretty bullish about how fast D.C. is moving away from dark, heat-trapping roofs. Roofs like the one Brendan Shane used to have on his house on Morrison Street in Northwest D.C.

Shane is walking up the stairs to the house’s top level which, today, has become playtime headquarters for Shane’s two sons and two of their friends. It’s something Shane says wasn't possible until he decided to redo his flat, black roof with energy efficient and white material.

Before that, he says the room simply wasn't usable, especially in the middle of summer.

“Yeah, it was just storage,” he says. “Over the course of the year, in the winter it was pretty chilly, and in the summer it was 90-100 plus degrees in the attic.”

This map, from a 2009 UC Berkeley study by Colleen E. Reid, shows D.C.'s most heat vulnerable areas (darkest red). It considered many factors, including the demographics of the local population (age, poverty level), the amount of tree cover in neighborhoods, and the amount of impervious surface across different parts of the city.

Shane was more motivated than most to make the change to an energy efficient roof — he happens to be the director of policy for the District’s Department of the Environment.

But he says anyone who’s thinking about a new roof really should go white.

“Right now, the cost should be about equal,” he says, “and the big issue really is education — most people can ask their roof installer for energy star options right now, and pay very little premium.”

And staving off the heat isn't just a matter of keeping comfortable; heat kills.

“We've found that on the average heat wave that lasts about four or five days, there’s about 10 additional deaths that wouldn't have happened without that heat,” says Shickman.

Shickman and his colleagues at the Global Cool Cities Alliance estimate D.C. will save 20 lives over the next decade if it continues to lighten its flat rooftop surfaces and plant more vegetation.

And he says D.C. has become a world leader in combating excess urban heat. The city now requires reflective roofing on all new buildings, and is actively working to give all flat topped city-owned buildings new, lighter roofing as well.

Brendan Shane says the tougher trick will be changing the roofs of all the city’s residential structures, but his department is starting to educate people now.

“You can't tell people to just go out and replace their roof anytime. They need to do it when the time is right,” Shane says. “We need to get everyone, industry and the city, on the same page, so that we know, starting now, cooler roofs will go in, and in 5-10-15 years, that'll make a big difference across the city.”

So the next time you get depressed about the state of our warming planet, maybe consider lightening up.

Music: "Summertime" by Dizzy Gillespie from The Real Thing

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