|A FANtastic Alternative|
|A FANtastic Alternative
On warm days when there is no breeze, it may be hard to get effective cooling from natural ventilation. Turning on a fan instead of an air conditioner can save money and energy. Fans create comfort by cooling the skin rather than cooling the air. There are three generic types of fans: attic vent fans to lower attic temperatures, whole house fans to promote fresh air exchange and air circulating fans to create air motion to increase comfort.
The attic fan speeds up the cooling process with the "chimney effect" of pulling air in through open windows, up through the attic and back outside. When the fan is on, air can be let into the attic by opening the attic door or by installing a simple louver that automatically lets air ventilate.
Whole house fans are another energy efficient option. They can reduce indoor temperatures by up to 20 degrees F, depending on the outside temperature. Whole house fans are usually installed in a hallway ceiling on the top floor of a house. Whole house cooling pushes the heated air out through the attic and draws in cooler outside air. The cooler air moves through the home to lower the temperature. The resulting pressure difference causes fresh outdoor air to flow into the home. Some whole house fans use the same amount of electricity as two incandescent light bulbs and vary in the amount of noise they make.
Air circulating fans°™ceiling, oscillating, or box fans°™help extend the natural ventilation seasons by keeping the air conditioning off during the spring and fall.
Cross Ventilation Breezes
Small, inexpensive fans help create comfortable cross ventilation breezes. To create an artificial breeze, open the windows on the shady side of the house and position a fan to blow out of a window on the warmer side of the house. The resulting pressure difference will cause air from the outside to flow through the house. While this option doesn't work well on very hot and humid days, it works surprisingly well the rest of the time.
Ceiling fans provide the greatest whole room circulation. Ceiling fans compliment ventilation cooling and supplement air conditioning. They also use about the same energy as an ordinary light bulb. Unlike window fans and smaller oscillating fans, most ceiling fans have a reverse airflow switch to either pull up cool air from the bottom of the room, or push down warmer air to create a breeze.
Generally speaking, larger fan blades mean greater air movement and quieter operation. A good ceiling fan should create enough air movement to cool the skin and provide comfort at 82 degrees F with 80 percent relative humidity. Using both the air conditioner and a ceiling fan can waste energy unless first raising the temperature setting on the AC unit. For the same reason, ceiling fans should not be left running in unoccupied rooms.
Getting rid of excess heat and humidity is especially important when trying to keep a home cool. Kitchen exhaust fans mounted above ranges help remove heat and humidity created during cooking in the same way that bathroom exhaust fans help remove heat and humidity caused from baths and showers. Food odors and oven heat can easily be removed within 15 minutes or less, but be careful; small exhaust fans can blow a houseful of cooled air outside in just one hour.
More Information and Additional Resources
Some of this information was adapted from the American Council on an Energy Efficient Economy's publication, Consumer Guide to Home Energy Savings, 7th Edition, the Energy Efficiency and Renewable Energy Network as well as Homemade Money by Richard Heede and staff of the Rocky Mountain Institute.
Additional information on home energy savings can be found in the Home Series: Home Cooling booklet available on the Iowa Energy Center's Web site, www.energy.iastate.edu or by calling (515) 294-8819.
The Iowa Energy Center is a nonprofit organization dedicated to improving Iowa's energy efficiency and the use of renewable fuels.