By Vincent Valk – Special to CNN
Let us suppose, for a moment, that it were somehow possible to remove the greenhouse gas emissions of 300 million automobiles around the world – without actually removing any automobiles.
How would we go about doing this? A massive cash-for-clunkers style program in which everyone gets hybrids? A vehicle-miles-traveled tax? Something involving solar and wind farms?
No – we can paint our roofs white.
Cool roofs technology could also help building owners save on electric bills – about $360 per year for a thousand square meters of roof, according to a presentation at a conference at the Lawrence Berkeley National Laboratory (LBNL) in California in July of this year. This isn’t much, but it adds up, particularly if it’s hot out. Cool roofs technology would reduce energy consumption in over 90% of the territory of India, according to another presentation at the same conference.
If 80 percent of the roofs in urban areas in the tropical and temperate climate zones were painted white (or some other "cool" color, which reflects non-visible light), it would offset 24 billion metric tons worth of carbon dioxide missions. This is the equivalent of our 300 million cars, or of 500 medium-sized coal power plants.
Hashem Akbari and Arthur Rosenfeld, researchers at LBNL, arrived at the estimate of 300 million cars by calculating the impact of the reduction of "solar heat gain" in buildings. Solar heat gain refers to the amount of energy absorbed by common dark-colored roofs, which heats up a building's interior and increases energy-intensive cooling costs. They found that painting 1,000 square feet worth of a roofs white offsets 10 tons of carbon dioxide emissions - scaling this up amounts to 300 million cars.
While large-scale white roof implementation would have a big impact globally, the local impacts vary depending on the climate. A 2003 study of eleven U.S. metropolitan areas by LBNL found that annual net energy savings would total $37 million in Phoenix, but just $3 million in Philadelphia. Still, savings are savings and all of it helps combat global warming.
Another presentation at the July conference discussed a new pilot project between LBNL, the Global Cool Cities Alliance (GCCA), the U.S. Environmental Protection Agency and the city of San Jose, CA. The project will involve the establishment of a "cool zone" in the city, with cool surface technologies, including cool roofs, deployed throughout an entire neighborhood. LBNL will monitor the impact of the cool surfaces on the local climate and energy consumption. The program may eventually reach the entire city.
GCCA itself, which was launched last year, has five "founding city members" on three continents, and is now working with R20, an association of regional governments aimed at developing low-carbon projects whose members represent local governments throughout the world.
Indeed, it is local communities that are taking the lead in implementing cool roof technology, and opportunities for that are practically limitless. Roofing and pavements (which are also typically dark colors) account for over 60 percent of urban surfaces. Roofs alone total about 20 percent to 25 percent. There are, literally, billions of square feet of dark-roofed surfaces in cities across the world, and white coatings are not difficult to find. It can take decades to scale hybrid cars or solar power; white roofs can scale quickly, as they require no new infrastructure aside from lots of white paint.
The ease of implementing cool roofs – which often literally means nothing more than painting roofs white – is what makes the idea so powerful, and attractive to communities. This is, unsurprisingly, especially true of communities with warm and sunny climates. California, to give one example, first required that new, flat roofs be painted white in 2005. The move was a no-brainer, according to Arthur Rosenfeld, author of the paper on global impacts change with Akbari and California Energy Commissioner when the rule came into force. "Everybody said…we should be doing this," he told me. Australia, too, has adopted solar reflectivity requirements – which, essentially, mandate cool roofs – in its most recent building code.
Regulations have, thus far, mostly covered new roofing only, but most roofs need to be replaced about every 20 years, according to Rosenfeld, so they'll eventually have a big impact. Voluntary initiatives like New York City's NYC Cool Roofs, or the White Roof Project, which encourages people to identify roofs to paint white across the US and looks for volunteers to paint them, are working to whiten roofs before they need replacing.
"Our main goal isn’t coating the roofs ourselves," says Juan Carlos P.E., founder of White Roof Project. "We want people in cities across the nation picking up their own brushes, and creating change in their cities. We want to help people have the tools and support necessary to make this happen everywhere."
If, indeed, this does happen everywhere, it will be as though 300 million cars have disappeared, at least in atmospheric terms. This is a great thing, though you'll still be stuck in traffic.