Dont get tooooo excited...
I put that white stuff on my roof....but as it collects dirt over time the heat comes back
But it does help bring temp down 10 deg or so .....
When I filled the whole roof with solar panels - I thought the shade would also help
seams the hot solar panels, even raised 2 " cancel out the shade effect
http://overthetopcargotrailer.blogspot.com/