So painting roofs and parking lots white has immediate cooling effects by reflecting sunlight while also reducing the amount of energy used for air conditioning, both directly in the affected buildings, and indirectly by reducing the urban "heat island" effect. Pretty cool (no pun intended). So why aren't we doing this yet? If we're going to be throwing money around at labor-intensive projects in the name of stimulus (and it's quite clear we're going to be doing quite a bit of that), we can at least lobby for comparatively commonsensical projects. Painting a roof white is a lot cheaper than installing solar panels, for instance. I'd be curious to find out how the energy produced by a solar roof stacks up against that saved simply by a white one.