> Part of the key to old houses staying cool was high thermal mass: lots of brick and stone that could stay cool during the day.
That only works if you don't have long hot spells. I live in a house with high thermal mass - reinforced concrete filled cinderblock. It was built by a commercial builder as his own house in 1950. There's enough thermal mass to keep the interior temp stable for three days. No need for air conditioning.
This worked fine until Northern California started having week-long stretches of 100F+ temperatures. That didn't happen until about ten years ago. Once all that thermal mass heats up to ambient, it won't come down for days.
I live in about a 200 year old New England farmhouse that’s a mixture of post and beam and stick. I definitely observe that for one or two hot days, especially with passably temperate nights, inside will definitely be cooler than out. But once the house heats up, it takes days to get it cool even if temperatures have gone down outside.
That only works if you don't have long hot spells. I live in a house with high thermal mass - reinforced concrete filled cinderblock. It was built by a commercial builder as his own house in 1950. There's enough thermal mass to keep the interior temp stable for three days. No need for air conditioning.
This worked fine until Northern California started having week-long stretches of 100F+ temperatures. That didn't happen until about ten years ago. Once all that thermal mass heats up to ambient, it won't come down for days.