If you’re looking for an inexpensive, environmentally friendly way to cool your home, consider using window fans. Window fans can cool your home when it is hot during the day and cool and dry at night. The fans will save you from running the air conditioner, which will lower your electric bills. To cool your home, use fans to pull cool outside air into the home at night, while other fans blow hot air out from inside the home.

Choosing Fans for Your Home

Choose square box window fans rather than other types. Box window fans have flat sides and blow air in a single direction, which makes them ideal for blowing a steady stream of air.

Select the largest fans that will fit inside your windows. A larger fan will move more air than a small fan. Look for fans that will take up at least two-thirds of the horizontal width of your window frame. Make sure that the fans will also fit within the lower portion of the window when the window is fully opened. Square fans aren’t too expensive. Usually $15-$30 per fan.

Purchase an even number of fans to maximize airflow. When you install the fans, some will be placed in windows to blow cool air inside and others will be placed to blow hot air outside. It’s best to have the same number of fans blowing in each direction.

Selecting Locations for Your Window Fans

Make sure your windows have screens are are not near areas of outside noise. Cooling your home with window fans is not recommended for homes without window screens, because insects or animals may enter through the open windows.

Install the fans in windows far from sources of bad smells. Take a look at the outside surroundings before you decide which windows to place your fans in. Fans that blow air into the house should not be placed near garbage cans or parking areas.

Place inward-blowing fans on the ground floor of your home. At night, the air near the ground will be the coolest. When you’re placing inward-blowing box fans, select windows that are on a shaded side of your home.

Install fans blowing outward on the top floor of your home. Fans located in windows on the top floor of your home will blow warm air outside. If you have an attic in your home, place the outward-blowing fans in attic windows and leave the attic door open. Place your outward-blowing box fans in windows located on the sunny side of the house.

Installing and Using the Fans

Close each window tightly around the fan to hold it in place. Open the window and place your fan in the windowsill. Make sure it’s balanced. Then, lower the top panel of the window until it’s securely pressing down against the top of the fan. This will prevent the fan from slipping out of place.

Cover the gaps on either side of the fans if they're smaller than the frame. The fans won’t be able to effectively cool your home if there are gaps between the sides of the window frame and the edges of your fans. Tape cardboard over the gaps on the side of the window or, pull out the plastic extender panels on the sides of the fan, if so equipped.

Turn on window fans at night when it’s cooler outside than inside. If it’s warmer outside than inside, your fans will blow hot air around. So, turn the fans on only when it’s cooler outside in order to bring in cool air and lower the temperature inside your home.

Remove the fans and close the windows when it’s warm outside. Close windows, blinds and drapes on warm days. Invest in some thermal drapes and blinds to reduce solar heating.

You can also drape a cold, wet towel or cloth over inward-blowing fans when it’s hot out. Select a size of towel that matches the size of the fan. The wet towel will dramatically increase the fans’ cooling performance for about 1 hour.

For more information on cooling your home with fans, visit WikiHow.