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Attic Vs. Whole House Fans

With winter behind us, many start thinking about how to keep cool in the summer months ahead. Keeping homes cool and dehumidified, especially in eastern Nebraska, is important for comfort as well as the overall health of the house. But memories of higher electricity bills due to air-conditioning systems running continuously have some seeking ways to reduce cooling costs while maintaining a pleasant indoor climate. Installing an attic or whole house fan is a common consideration.

A whole house fan and an attic fan perform similar functions; both ventilate and cool the house. However, there is one major difference between the two: the areas they address. A whole house fan pulls air from the entire house, drawing it into the attic. An attic fan draws out air from the attic only, sending it outside. Both options deliver positive results as well as negative consequences worth mulling over.

A whole house fan is an electrically powered fan that pulls fresh air through all of the home’s windows and sends it into the attic. One centrally located fan in the ceiling of the top-most floor can change out the air in the house three to six times per hour, depending on the size of the house and the fan’s capacity. The ceiling vent’s louvers open and close in response to the fan’s operation.

However, if anyone in the household is susceptible to air pollutants or has respiratory concerns, outdoor air should be filtered before it is brought into the home. Since whole house fans require opening windows, filtration is not possible.

Next, note that many homes in Nebraska have basements that tend to be cooler than upper floors. If the outdoor air has a higher relative humidity than the basement, water vapor can condense to create an environment for mold and mildew to grow. While this problem can be mitigated by running air conditioning or dehumidifiers, the opportunity to save energy is lost.

Finally, a whole house fan requires the user to open windows, then switch the fan on. If the process is not reversed before the heat of the next day returns, outside air will easily enter the home and negate any savings. Consider how easy it is to forget to close one window!

In turn, attic fans are usually activated by a thermostat located within the attic. If an attic is not adequately insulated, an attic fan can help cool down the living space by reducing the heat transferred through the ceiling below. To cycle properly, unrestricted air intake must occur through venting in the soffit or, under eaves or fascia areas. Inadequate intake air can cause cool, conditioned air to be drawn through ceiling penetrations for electric connections or recessed can lights and causing air conditioning to run longer.

As you can see, while both types of fans use considerably less energy than traditional air conditioners to reduce cooling costs, both can potentially to increase energy use. Your local utility can help identify other ways to keep your home cool and comfortable this summer while providing reliable, low cost and sustainable energy. For more ideas or information about EnergyWiseSM energy efficiency incentives, contact your local public power utility.

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