My house in Dallas only rose by about one degree per hour during the day when the A/C was off, even on the hottest days. It was pretty well-insulated, and the large trees around it helped.

> humid Texas summer

This is probably the warped idea of "humid" I got from growing up in South Florida, but Dallas was rarely ever humid.

Dallas is relatively humid, but not Florida, no.

It also doesn't have the constant sea breezes and incidental rain that most of Florida enjoys.

Build your houses out of stone rather than wood, and they'll have a 10+ tonne thermal mass. Just a few inches of insulation around that on all sides, and the temperature barely varies day to night.

Houston is as humid as it gets though.

Similar latitude actually. My house is concrete block though so it tends to resist temperature change a bit.

Also keep in mind large buildings will resist temperature changes even better than houses due to their size. Less surface area per volume.

Good insulation is a great investment for any home. Keeps your house cooler in summer, warmer in winter, dramatically reducing your energy needs in both cases.

Our house went from 78 to 85 in 48 hours with the AC completely off. With highs over 100. We have an old house with basic insulation upgrades.

I'd expect it is a combination of insulation and thermal mass.