Energy Efficient Ventilation With Circulating Fans

Circulating fans include ceiling fans, table fans, floor fans, and fans mounted to poles or walls. These devices create a wind chill effect that will make you more comfortable in your home, even if it’s cooled by natural ventilation or air conditioning. Ceiling fans are considered the most effective.
 
If you use air conditioning, a ceiling fan will allow you to raise the thermostat setting about 4°Fahrenheit with no reduction in comfort.   

In temperate climates, or during moderately hot weather, ceiling fans may allow you to avoid using your air conditioner all together. Install a fan in each room that needs to be cooled during hot weather.
 
Ceiling fans are only appropriate in rooms with ceilings at least eight feet high. Fans work best when the blades are seven to nine feet above the floor and 10 to 12 inches below the ceiling. Fans should be installed so the blades are no closer than eight inches from the ceiling and 18 inches from the walls.
 
Larger ceiling fans can move more air than smaller fans. A 36- or 44-inch diameter fan will cool rooms up to 225 square feet, while fans that are 52 inches or more should be used in larger rooms. Multiple fans work best in rooms longer than 18 feet. Small- and medium-sized fans will provide efficient cooling in a 4–6 foot diameter area, while larger fans are effective up to 10 feet.
 
A larger blade will also provide comparable cooling at a lower velocity than a smaller blade. This may be important in areas where loose papers or other objects will be disturbed by a strong breeze. The fan should also be fitted to the aesthetics of the room—a large fan may appear overpowering in a small room.
 
A more expensive fan will operate quietly and smoothly and will probably offer more trouble-free service than cheaper units. Check the noise ratings, and, if possible, listen to the fan in operation before you
buy it.

Source: U.S. Department of Energy Office of Energy Efficiency and Renewable Energy