When I was a kid, we didn't have any air conditioning in the house. I grew up in Upstate New York, so it wasn't common to have A/C unless you lived in an apartment, or were really rich! My mom had one window A/C unit in her room. That was her one cool retreat.
She liked it really dark in the house in the summer to keep things cooler. She had roller shades on the windows, kept the shades down, curtains drawn, lights off, the whole works. We tease my mom that she is a vampire because she's such a night person. She loves to stay up late and sleep all morning. Its common knowledge that you don't want to call Jeanette during the AM, or you run a serious risk of getting yelled at.
Mom and Dad have air conditioning now. But now that I live in the South I have adopted some of my mom's cave dwelling style summer living. It really does keep the house cooler if you shut the shades, and turn off the lights. I am going to draw the line at sleeping in though, but believe me, if it wasn't for the alarm clock going off for work I might try that too!