I considered going light on my last roof replacement to reduce thermal absorption. Going a little lighter would have made almost no difference. To make a difference, the roof would have been close to white. It would have worked to reduce thermal absorption but damn would it have been ugly (roof is very visible on this house) and cost was way up so I doubt savings would ever have happened. If I had a flat roof, white would have made a bigger difference with less downside.
The coating in the article appears to make the biggest difference at night. I doubt it would have a noticeable impact on an individual house (feel or bills) but could help reduce the heat island in a city. With a few more generations of development, maybe it could be applied via crop duster and the city coated in it.
