When air conditioners first came on the market, they weren’t to cool homes but rather for quality control for industry. The fact that factory/industry workers were kept cool was just an added benefit!
The most pre-historic, pre-air-conditioning method of living was the cave – where temperatures averaged in the 50s throughout the summer and winter. But as mankind expanded, caves weren’t quite easily found. Post-cave housing used thick stone or brick to duplicate the temperatures that cave dwelling offered but air conditioning allowed the use of cheaper and lighter materials.
Older homes with more than one story took advantage of the stack effect (air moving into and out of buildings) as open stairwells vented heat upstairs. That’s why upper floors were only used at night, with the windows open. Some houses even had a tower or turret to act as a windcatcher or heat exhaust vent.
Shade trees planted on the east and west sides of a home block the summer sun before it warms the home exterior. They also cool down breezes slightly before they enter the porch area. Awnings and window overhangs provide the same effect, and let more sunshine in during the winter, when the sun hangs lower.
People had other personal methods for keeping cool, such as hanging wet laundry in doorways, sleeping in refrigerated sheets, and keeping one’s underwear in the freezer.
Years ago when air conditioning wasn’t universal, we were sometimes miserably hot. But “miserable” is a relative term. We didn’t know what we were missing, and we were used to it. We were never as miserable as someone in a small modern home built for artificial climate control when the air conditioner fails!
After WWII home air conditioning became widely available and helped usher in the age of the great baby-boomer, suburban expansion.
Source: Life Before Air Conditioning at Mental Floss