> And then they keep that coolness in using good insulation (neither of which were available in the ancient world).
Good insultation to keep cool in summer and warm in winter used to be provided by thick stone walls, which have quit some thermal inertia.
Just look at traditional houses in Southern Europe, for example. They are cooler than 'modern' houses because of that and because people nowadays insist on having a lot of glass (large windows, large patio sliding doors, etc), which turns buildings into greenhouses (and walls are thinner)... and then people install air-con to compensate.
Traditionally houses didn't have a lot of windows because glass wasn't as good as it is today when it comes to insulation. Triple glazed windows are becoming a standard in a lot of places.
People also didn't spend that much time indoors because they didn't have anything to do. Times have changed and the needs of the people have changed.
Walls being thinner nowadays is due to the advances in options available for construction & insulation, not to mention safety standards. Modern ceramic bricks with air pockets + 10cm of polystyrene on the outside for insulation is insanely efficient for most residential establishments.
I may be wrong but I feel thick stone walls are a bit like having large buckets of water in a greenhouse: They regulate temperature, whereas modern insulated walls don't because they are indeed just very good insulators.
As for double or triple glazed windows, they are good at keeping the heat in but in my experience they are not that good at keeping the heat out: sunlight gets in and heats up surfaces, the whole room warms up, and then the heat is trapped.
A traditional way to try to keep cool in Southern Europe is to open the windows to create airflow while closing the shutters to keep sunlight and heat out. Now, of course this makes rooms quite shady. Villages completely quiet with shutters closed during 'siesta' are famous to the point of stereotype but that's a real adaptation: Stay cool and avoid efforts during the hottest part of the day.
Good insultation to keep cool in summer and warm in winter used to be provided by thick stone walls, which have quit some thermal inertia.
Just look at traditional houses in Southern Europe, for example. They are cooler than 'modern' houses because of that and because people nowadays insist on having a lot of glass (large windows, large patio sliding doors, etc), which turns buildings into greenhouses (and walls are thinner)... and then people install air-con to compensate.