I think it's a cost-benefit balance. Anecdotal, but when you see things bleached by the sun, they're pretty white -- not ultra #FFFFFF white, but pretty white.

I think it's a cost-benefit balance. Anecdotal, but when you see things bleached by the sun, they're pretty white -- not ultra #FFFFFF white, but pretty white. My roof is done with a modern membrane, which is very light gray in appearance, with tiny white stones embedded in it. I imagine you can take a roof like that (say 80% albedo) vs a high-tech ultra-white (99.9% albedo), and the 80% roof won't degrade in reflectiveness because the sun naturally bleaches things to that level -- but the wear and tear of high-tech roof will bring it down to about the same. Just musing here, no solid evidence to support this.