Tips on Cooling Your Home with Window Fans

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Published August 6, 2010 | Updated August 4, 2015

In a time when everyone worries about their energy consumption, window fans are the economical and energy-wise way to cool your home. Window fans are often used to supplement air conditioners, but if used properly, they can even replace your air conditioner, all while saving you money and energy. Follow these tips to effectively cool your home with window fans.

Using Window Fans:

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  • Fan Direction

    The most effective way to cool your home with window fans is to use them at night to bring cool air inside and during the day to push hot air outside. For this method to work, you need a balance between the fans pushing air out and fans bringing air in. An equal number of fans between the two is ideal, but if that's not possible, have more fans blowing air into your home.

  • Fan Placement

    Place inward-blowing window fans on the cool sides of your home that see lots of shade. Try to work with the prevailing wind direction for more cool air.

    If you live in a single-story home, place all inward-blowing fans on one side of your home and all outward-blowing fans on the opposite side. Also, keep as many inside doors open as possible for maximum air flow.

    If you live in a multi-story home, place inward-blowing fans on the lower floors and outward-blowing fans on the upper floors. This method will rid your home of the warm air rising to the upper stories. Remember to open as many interior doors as possible for air flow.

  • Fan Placement to Avoid

    Some situations to avoid are inward-blowing fans near garbage or parking areas, in offices, above valuable items, or near refrigerators and freezers.

    Inward-blowing window fans near garbage or parking areas will bring those smells and fumes into your home; in offices, they will disrupt loose papers; above valuable items, they can lead to water damage if the window fan is still in place during rain; and on refrigerators and freezers, nearby window fans can blow the cool air out of the unit quicker than usual when you open it, which increases the load on the appliance.

  • Fan Size

    For maximum efficiency, each window fan should be the biggest size of fan that will fit in each particular window. You should also use paper, cardboard, or drapes to block the gaps between the window and the fan. This prevents air that has already come through the fan from moving around the fan and through it again. Blocking these gaps is especially important for inward-blowing fans, since the change in pressure will make the air try to go back outside.

  • Fan Running Time

    The key to using window fans as a cooling method is to bring fresh air into your home anytime the air outside is cooler than the air inside. When the inside air is cool enough to offset the predicted daytime temperature, turn off the fans, remove them from their windows and then close the windows.

    The rule of thumb is that the inside daytime temperature will be the average of the outside daytime temperature and the inside nighttime temperature. For example, if you want to keep your inside daytime temperature around 70 degrees Fahrenheit and are expecting the outside daytime temperature to be around 80 degrees F, you need to cool your house to about 60 degrees F at night.

Window Fan Tips and Warnings:

Temperature Variation: Bringing in cool air at night and pushing out hot air during the day means you may experience 10 to 20 degree F temperature differences between day and night. This daily fluctuation in temperature and humidity may be uncomfortable.

Climate Influences: If the nighttime air in your area is uncomfortably hot, humid, or polluted, this method probably isn't for you.

Safety Concerns: Make sure your windows have adequate screens. Windows with weak, ripped or missing screens can become a point of entry for insects, small animals, or criminals.

Weather Influences: Don't leave your window fans in the windows during a rainstorm. This can lead to water damage, electrical damage, or fire inside your home.