White roofs are a great idea
I have thought white roofs were a good idea years ago, but our HOA will not let you do it.
Attics in Houston get hot enough to turn Christmas candles flat.
I have thought that a shade (second roof) over the roof, that was open at the base and up on the ridge, would help keep homes cooler. I am sure the HOA would be against those as well. The extra weight might bee too much for the structure, but they could do it on new homes.
