Research Matters

Research Matters

White Roofs


Using a new computer model, KU's Johannes Feddema and other scientists affiliated with the National Center for Atmospheric Research have demonstrated that simply painting city roofs white would slash temperatures in urban cores.

Aired February 21, 2010



2 minutes (2.7 MB) | Download mp3

Transcript


Research shows that white roofs effectively cool cities, but aren't needed in all parts of the world. From the University of Kansas, this is Research Matters. I'm Brendan Lynch.

Anyone who has passed a scorching summer in a dense metropolis knows that in cities asphalt, brick and concrete soak up heat and boost temperatures. Johannes Feddema is a professor of geography at KU.

Feddema: Cities are known to be warmer than the surrounding environment. The geometry of the city - the buildings' shapes - traps solar radiation. And water tends to be removed from the city environment, so it's not available to evaporate and cool the city.

Now, using a new computer model, Feddema and other scientists from the National Center for Atmospheric Research have demonstrated that simply painting city roofs white would slash temperatures in urban cores.

Feddema: Cities use a lot of blacktop and they absorb a lot of radiation. If you make a highly reflective surface, it won't absorb as much radiation. By taking black roofs and changing them into white you can reduce the amount of energy that's absorbed in an urban environment, reduce the urban heat island, and also reduce the energy load on a building.

The report by Feddema and his colleagues indicates the world's cities would cool by an average of 0.7 degrees Fahrenheit each under all-white roofs. But the researcher cautioned that painting roofs white is not a one-size-fits-all remedy for rising urban temperatures.

Feddema: You have to think carefully about where and when you'd implement a policy on white roofs. Globally, energy consumption went up in our model because even though you made hot places cooler, this was offset by the need to warm more places in the wintertime and use more energy. The need for heating was bigger than the cooling gains.

For more on the cooling effect of white roofs, log on to Research Matters dot K-U dot E-D-U. For the University of Kansas, I'm Brendan Lynch.

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White Roofs

Research shows that white roofs effectively cool cities, but aren't needed in all parts of the world.

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