Lighten Up: Energy Department Pushes ‘White Roofs’ Campaign
During the 2008 presidential campaign, Republicans ridiculed candidate Obama when he held up a tire gauge and urged Americans to raise fuel mileage by keeping their tires inflated. How dumb could he be? You can’t solve the nation’s imported-oil problem that easily, his critics chortled. But of course, he wasn’t proposing to solve the entire problem that way — just suggesting a small but inexpensive step in that direction. If you were running a marathon, you wouldn’t deliberately carry a brick on the theory that dropping it wouldn’t improve your time all that much.
The same goes for another small but sensible step in pursuit of energy efficiency, one that Energy Secretary Steven Chu has been touting for months: whitening up the nation’s roofs. Most roofs in the U.S. are made largely of asphalt or tar — dark-colored materials that absorb the Sun’s energy quite efficiently. (That’s actually redundant: they’re dark because they absorb rather than reflect light). The buildings beneath them get hotter as a result, and air conditioners have to work all that much harder to cool things off. Beyond that, the extra heat makes the entire urban area warmer than it would otherwise be, something known as the urban heat island effect.
A dark roof is like a marathoner’s brick or an underinflated tire: it creates unnecessary work. And of course, long before air conditioners had been invented, people in hot climates — Greece, southern Italy, North Africa — were painting their entire houses white to keep from roasting.
Long before air conditioners had been invented, people in hot climates — such as in Fira, the capital of the Greek Aegean island, Santorini — were painting their entire houses white to keep from roasting.
So Secretary Chu has been touting the idea of white roofs, and just a couple of days ago, researchers at the Energy Department’s (DOE) Lawrence Berkeley National Laboratory (LBNL) in California published a new study quantifying how effective white roofs can be. Their analysis, which was published in Environmental Research Letters, is based on maps created by NASA’s Goddard Space Flight Center of topography, cloud cover, and other factors. It suggests that whitening both roofs and road surfaces in cities with populations of a million or more could save as much energy as you’d get by taking 300 million cars off the road for 20 years.
Of course, cooling off your house is exactly what you don’t want to do in winter. It turns out, though, that the extra energy you need for heating in winter is significantly less than what you save in summer — largely because in places with cold winters, the sun angle is lower and the day shorter at that time of year, so there’s much less sunlight to reflect.
It may not be a coincidence that Chu was director of LBNL before ascending to run DOE, and the secretary can’t have been disappointed to see this result.
It may also not be a coincidence that Chu issued new orders this week: henceforth, all new DOE buildings will have white roofs, and old ones will be upgraded, unless the cost is prohibitive. He urged other federal agencies to follow suit.
The idea is so straightforward and non-controversial that even Anthony Watts, who’s often seen as a climate skeptic, headlined his blog on Chu’s announcement: “Cooler white roofs — no complaints there.”
No comment from Watts yet — or Chu, for that matter—about another make-it-white-to-cool-it-off project now being financed to the tune of $200,000. After placing near the top of a World Bank competition, Peruvian environmentalist Eduardo Gold is painting some Andean peaks white to slow the disappearance of glaciers in the Andes. The Peruvian equivalent of Lawrence Berkeley National Lab — if there is one — hasn’t yet announced plans for a study.