Fans can be surprisingly efficient in cooling homes if used properly, and cost much less than an air conditioning system to run. Running fans in historic homes built before 1950 also requires much less retrofitting- generally just some maintenance to better insulate and vent, especially in attic spaces.
Did you know you need to change the direction of the airflow from fans depending on the time of day or year?
If you have ever been in an argument about which direction a box fan in a window should face, you may be surprised to learn that box fans should be flipped around depending on the time of day. During the daytime, face box fans in windows outward to force trapped hot air inside the house out, especially on the upper floors of the home. After dark, flip the fans back around so that the cool nighttime air is pulled inside to cool. If you have windows that open at the top, popping these open at night will also help with this circulation.
Ceiling fans should be set to spin counterclockwise in summer, which will force cool air downward. In winter, these same fans should still be set to run, but should be set in a clockwise rotation; this will help circulate the heating evenly throughout the room.
You can also install a whole-house fan; this will require a bit of retrofitting of the attic space, but will pull and circulate the air flow of the entire house, improving indoor air quality and helping to very efficiently cool everything off.
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After dark, flip the fans back around so that the cool nighttime air is pulled inside to cool.