June 2019 EnergyWiseSM Tip: Household Fans

04-Jun-2019

By: Energy Efficiency Program Manager Cory Fuehrer

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 EnergyWiseSM, along with possible energy efficiency financial incentives, contact
Southwest Public Power District or visit www.nppd.com.


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