That's not entirely true. In Bulgaria, even during the hottest summer days, you go into a traditional stonewall building and it is cool inside with no mold as w

That's not entirely true. In Bulgaria, even during the hottest summer days, you go into a traditional stonewall building and it is cool inside with no mold as walls are whitewashed. In some newer traditional houses, the first floor is dug half in the ground, which also keeps the first floor cooler in the summer and warmer during the winter, and it's where the living room typically is.