I wasn't able to find any other diary entries on this, and there seem to be a number of people who have the wrong impression about Stephen Chu's energy efficient roof proposal. Yes, he did use the term "paint your roof white," however this is really a layman's way of saying "make your roof reflective of solar radiation." There's no need to actually paint your roof "white," and this could actually have a worse result than much more asthetically normal shingles. It's not about being a certain color, but being energy efficient.
Following what Stephen Chu said, the media largely reported it as: "Stephen Chu and Obama want to make your house ugly and paint your roof white!" Rush Limbaugh and the rest of them rightly attacked this proposal as silly and unecassary. But, of course, they were not actually attacking what Stephen Chu meant. Based on his following clarifications and general DOE policy the intent was actually to make roofing energy efficient.
The above house is built using energy efficient shingles with a reflectance of .27. Traditional black shingles have a reflectance in the range of .05, making new energy efficient shingles over 5 times more reflective. Normal white latex paint could have a reflectivity of as low as .25 - so simply painting your roof white could be worse than nice looking grey shingles (Note, these are not normal grey shingles, they are specially reflective of infrared). Ongoing research by physical chemists towards stable, reflective coatings with a normal visible color spectrum may eventually result in grey shingles with much higher reflectivities.
Regarding the sometimes mentioned "flat roof" comment, what was meant with that is smoothness of the surface - not angle to the sun. Smooth would have been a better word choice.
Out of curiosity, I checked Rush Limbaugh's house in Florida (via Google earth) and it does have very light colored grey shingles, so he's already basically following Chu's advice.
Sources:
http://hes.lbl.gov/...
PDF Technical Details for Elk Corp Energy Efficient Shingles
EDIT: You really don't gain much from a black roof in the winter. Even in northern Tennesse you still get 42% less solar energy in the winter. In Florida that % shrinks, but you would hardly ever heat there anyway.
So with a "white roof" you're not missing that much solar energy in the winter, because there isn't much to be had. But you are comming out way ahead in the summer, for all the AC you save. Ontop of that, in some cases you actually will also have lower heating costs with a less absortive roof, due to black body radiation (This is one of the reasons arctic stations are usually white). A roof that you could switch between absortive and non-absortive would of course be the best of all worlds!
You can calculate what the rough amount for you is here:
Department of Energy "Cool Roof" Calculator
Also, poll should be elastomeric, not elastometric.
Final Edit: Of course there are metal roofing materials and many other solutions for a cool roof that need not be painted "white." Indylisa recommended the following site for anyone interested: http://www.pstvnrg.com.