Modern residential architecture is designed around the notion that an HVAC system will be utilized to artifically control the environmental conditions of the building as the occupant so desires. Unfortunately such design almost always excludes natural ventilation should the power go out. The result is a house that gets hot in the summer and does not have enough natural airflow to keep the inside reasonably comfortable. I learned this when I bought a house built in 1920, and saw how I could sit in the house through the summer with little more than a couple window fans going, while neighbors who'd rebuilt or drastically remodeled were not so fortunate. Homes built prior to the advent of consumer HVAC were designed with this consideration in mind, and so they stay much more hospitable than the newer strip homes you see with fewer windows, inadequate ventilation, and compartmentalized living spaces which prohibit air flow.

Even in older homes I would still rather have at least a window ac unit in the summer. Then again, my internal thermostat has always been about 20 degrees cooler than the average, so I don't mind living in a home only 60 degrees warm. If I can at least have a fan on me, I can tolerate the heat, especially trying to sleep at night.