A very cheap and easily implemented idea to help with climate change. That could be done in huge swaths of the world where a lot of people currently live. It probably needs some government help to stir people into action or make them aware of it. A tax break maybe for painting your roof white in a hot country/state?

In northern latitudes it would be nice to be able to change the albedo of the roof to reflect energy in the summer and absorb it in the winter (although the effect in winter will be muted in places where snow accumulates on the roof.) I wonder if there exists anything like that.

Thats interesting, thanks for pointing it out