Hot weather means Nebraska households will try to find ways to beat the heat without driving up air conditioning costs. If used properly, fans help manage these costs while maintaining indoor comfort. But used incorrectly, your next electric bill might be a shocker!
During the air conditioning season, household fans are used for two primary purposes: circulation and ventilation. More on the pitfalls of ventilation later.
According to www.energy.gov, circulating fans include ceiling, table and floor fans, and fans mounted to poles or walls. These fans create a wind chill effect that makes people more comfortable in their home, even if it's only cooled by natural ventilation or a small window air conditioner.
While air conditioners use compressors and refrigeration cycles that are much more energy intensive, fans only move air and require much less electricity. Their energy saving opportunity becomes more important when considering human physiology and thermodynamics. By blowing air around, the fan makes it easier for the air to evaporate sweat from your skin, which is how you eliminate body heat. The more evaporation, the cooler you feel. If a room’s air is well circulated, the process is improved.
Ceiling fans are considered the most effective at room circulation. According to a study by the Department of Energy, ceiling fans enable occupants to raise the thermostat setting about 4°F with no reduction in comfort. During those times when it’s just slightly warm in a room, ceiling fans allow people to avoid using the air conditioner. But too often, people forget to switch ceiling fans and other circulation fans off when leaving a room for an extended period of time. Fans cool people, not rooms, by creating a wind chill effect on their skin.
Table, floor, pole and other fans provide effective air movement in a particular direction or area. Often, they can be used to move cooler air from cooler parts of the home to the rooms being occupied.
Now, for those “other” fans: the ventilators. When effectively used, they can help manage home cooling costs. Unfortunately, overuse or misuse can increase air conditioning costs.
Window fans are a classic example. When the sun sets and outdoor air cools, window fans use little energy and can provide effective cooling to a stuffy home. They are best mounted in windows facing away from the prevailing wind and exhausting hot air from inside. Tightly close windows near the fan and open windows in rooms far from the fan. Windows near cooler shaded outdoor areas provide the best intake air. But when the fan is forgotten or the window is left open and the hot sun of a new day is bearing down, the cooling effects of the night before are quickly lost, and air conditioning must take over.
Bathroom fans are excellent for removing hot, humid air after showers and baths. Unfortunately, these fans often run much longer than needed to remove excess moisture. As they continue to operate, they exhaust cooled, indoor air at the rate of 60 to 180 cubic feet per minute until turned off. To prevent this from happening, install a timer switch with a maximum of 60 minutes. This should keep the fan running for at least 10 minutes after you leave the room to remove excess humidity.
Cooking can create lots of extra heat and humidity in the kitchen. If you must use ovens, cooktops or other heat intensive appliances during hot weather, a ducted kitchen exhaust fan is a must. Like a bathroom fan, they are ideal for removing extra heat and moisture out of the conditioned space. But over-ventilating is even more of an issue because many kitchen exhausts can move 90 to 350 cubic feet per minute. This can require up to one ton of your home’s air conditioning capacity to replace!
Finally, many people assume attic or whole house fans are guaranteed to save on cooling costs. The idea is the attic gets very hot because there is not enough ventilation. In turn, that heat seeps through the ceiling into the living space below, which then requires air conditioning to cool the room. These fans are often installed with an entry louver at the other end of the attic and a thermostat switch, so they only operate when it gets hot. What the homeowner doesn’t consider is that the fan is drawing air from ALL places it can, not just the entry louver. That includes through the ceiling of the room below. This is possible through gaps around light fixtures, ductwork and other penetrations. Without realizing it, the need for replacement air conditioning can offset the benefit of a cooler attic. Other means of attic ventilation, insulation and sealing are much more cost effective.
Your local utility and Nebraska Public Power District want to help you make the most of your energy dollars by reducing cooling costs. For more ideas on how you can make your home or business EnergyWise℠, along with possible energy efficiency financial incentives, contact your local utility.
As Nebraska switches from heating to cooling season, we usually enjoy a few short weeks without continuously hearing our home’s HVAC system running. But it won’t be long until the rising mercury has our air conditioning systems buzzing.