I realise you're reasoning from a general architectural standpoint, but if you rent, basement apartments are a nice hack. I rent one and it stays perfectly cool

I realise you're reasoning from a general architectural standpoint, but if you rent, basement apartments are a nice hack. I rent one and it stays perfectly cool even on 30 degree days just because there's much less wall to get heated by the sun. There are definitely tradeoffs though; more bugs and spiders, and flooding might be an issue depending on location. As for the architecture, one ancient trick is to paint houses white.