Ask HN: Why don't houses in California have white roofs?

I don't know all the details, but I do know it's only been a legal requirement for businesses in California and only since 2008. There are probably criteria that include/exclude buildings, but that is just a guess. There are no legal requirements to do this for homes. Also just a guess, but if there are no legal requirements to do it, roofers will use what is easiest to get, most abundant and most commonly used to remain competitive. Armstrong sells a white insulated foam roof for homes but it costs more. My neighbor said it pays for itself so I think they agree with you.

> A study done at Stanford University shows that white roofs may actually increase, not decrease, the earth’s temperature. White roof membranes have high reflectivity that directs heat upward into the atmosphere and then mixes with black and brown soot particles, which are thought to contribute to global warming.

https://m.huffpost.com/us/entry/us_2901288

Tesla's solar tiles is a good start. Alternatively, a tile that can be switched between white in summer and black in winter would be ideal.