This is why I love LBL so much:
One of the senior scientists at Lawrence Berkeley National Laboratory, Hashem Akbari, is trying to counter the effects of climate change by making all rooftops and paved surfaces white, or at least cool gray colors to reflect the sun’s rays, instead of attracting and absorbing heat. (We were talking about this today in CEE 176A as well: how much heat gain comes from the color of the roof tiles. Plus it is cheaper than a green roof… although I do love the idea of a green roof.) Akbari is hoping to launch a 100 Cool Cities program, where the hottest urban municipalities internationally would convert government-owned buildings to white roofs and offer homeowners incentives to make the switch.
The concept of painting homes and buildings light colors to reflect heat is an old one. Growing up in Tehran, Akbari recalled large white structures in the desert that captured night wind to cool the building, keeping the people inside comfortable. Homes built along the banks of the balmy Mediterranean are still painted white to this day (Greece anyone?).
In one study of a “heat island” – a densely packed urban area – Akbari and his team focused on the Los Angeles Basin and found that if all black surfaces were converted to white, the surface temperature could drop as much as 5 degrees. With cooler and cleaner air, a domino effect would occur: Less smog and pollution means fewer health problems, which lead to savings in medical bills. A cooler temperature also means less air conditioning, lower energy use, lower utility bills and so on.
In September, Akbari and his team published a study in the academic journal Climatic Change, which found for every 100 square feet of black rooftop converted to white, a building owner could offset about 1 ton of carbon dioxide. Add to that all the world’s paved urban surfaces (Akbari recommends converting black asphalt to an aged concrete color instead of white), and the team concluded enough cooling benefits to offset 44 billion tons of CO2…Â that’s roughly the same amount of CO2 the planet emits every 18 months.
But it would probably take at least 20 years for worldwide conversion, if not more and California is the only state to embrace white roofing, at least on commercial projects (Title 24: a new building standards law that requires all builders and owners of commercial flattop roofs to first consider cool colors for major retrofits or new buildings). The roofing industry has responded well, designing new materials and cooler colors to appeal to builders and home owners who are seeking cost savings and ecological benefits.
So, we should have a white, or light grey or terracotta roof, if not a green roof (which would help with stormwater mitigation, reduce heat island effect, reduce cooling load, give the roof a higher R-value, and increase the life of the roof membrane)…
and maybe even a wind tower??
Here is the article for reference (thanks to my mum): http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2009/02/20/DDTL15VQAG.DTL