Fans
Below are some frequently asked questions about household fans. Choose a category to the left to view the related questions and answers.
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Q: What is the correct setting for ceiling fans: clockwise or counterclockwise?
A: The correct direction of the fan depends on the manufacturer and the
slope direction of the blades. During the summer, air movement should be downward,
blowing the air on you and causing a wind chill effect. For most ceiling fans, this means
operating them in a counterclockwise direction.
Q: We were told that the insulation in our home is so good and the house so
well-sealed that an exhaust fan was installed for air circulation. It runs constantly, day
and night. Since we are in and out of the house constantly, leave doors open frequently
and always have a window open at night, is the exhaust fan really necessary?
A: Some modern homes are built so well that the use of air exchangers
is recommended to ensure a healthy internal environment, but very few actually meet this
tight standard.
Aside from the small leaks and cracks around doors, windows and other penetrations, the
duct work used to distribute your heated and cooled air is notorious for varying degrees of
leakage. When combined with an environment where doors are left open and at least one
window is open at night, there isn't much reason to run the ventilator fan.
Q: We have ceiling fans in nearly every room in our house. Is it efficient to run
them all to keep the whole house cool, or should we just run them in rooms that are
occupied?
A: Ceiling fans do not produce cooling themselves; in fact, they
actually add motor heat to the space. The benefit of a ceiling fan comes from its ability
to create a windchill effect. It does not lower the room temperature. This windchill effect
makes you feel cooler by accelerating the evaporation of moisture on your skin.
When used in conjunction with your air conditioner, a ceiling fan can lower energy costs
by allowing you to set your air conditioner's thermostat at a higher temperature. Since
the true value of a ceiling fan is to accelerate personal evaporation, you should operate
them in occupied rooms and turn them off in unoccupied rooms.
Q: We are away from our home all summer and leave the air conditioner set at
about 90, but we have never left the ceiling fans on. Would leaving them on all summer
when we're away reduce our cooling costs?
A: Operating your ceiling fans during the summer will not reduce your
cooling costs. In fact, it will actually increase your electric costs due to the added cost of
operating the fans.
Ceiling fans do not produce cooling themselves; they actually add motor heat to the space.
A ceiling fan cools by creating a windchill effect, but it does not lower the room temperature.
Since the value of a ceiling fan is to accelerate personal evaporation, it makes no sense to
leave them on when your are away from your home.
Q: To reach a more constant temperature and lower cost, is it more efficient
to leave our thermostat's fan setting on "auto" or "on"?
A: If you're aiming for more air movement, use ceiling fans or regular
portable fans instead of using your air conditioner's blower.
Your air conditioning unit normally runs about 50% of the time to cool your home during
the height of the summer. Running the fan during times when the unit is not operating
increases your monthly cost much more than does the cost of operating a ceiling fan
24 hours a day, 30 days a month.
Another thing to consider regarding the operation of the air conditioner's blower is that
any leaks in your duct system will allow hot attic air to be introduced into the air stream,
adding more heat to the house.
Q: Are whole-house fans worth the trouble to install?
A: In the Southwest, homeowners can run their evaporative
coolers on fan-only and perform basically the same function as a whole-house fan.
To ensure that a whole-house fan does not negatively impact summer air conditioning
loads, you must install it so that it is possible to completely seal off the fan when
running the air conditioning. Any leak around the fan enclosure or through the closed
grill can increase the air conditioning load and negate any savings realized by the
installation of the fan.
If the fan is properly installed, using it during the months when daytime temperatures
are still in the 90s and 100s and the night temperatures are in the 60s and 70s can
inexpensively bring the temperature of your block walls down to comfortable levels.
Since block walls retain heat, your air conditioning unit will still be operating even
when the outside temperature is well below your thermostat set point. Without
some type of whole-house ventilation system, there is no efficient way to bring cool
outside air into your home.
When shopping for a whole-house fan, look for one that will fit between your trusses
and has air volume specifications that meet your needs.
Q: Can ceiling fans be used in the winter for any beneficial purpose?
A: A ceiling fan can help lower energy consumption in the winter by
up to 10%. The temperature of the air in a heated room varies in layers: The air near
the ceiling is warmer than the air near the floor because warm air rises.
A ceiling fan can help push the warmer air that is trapped near the ceiling back down into
the room, thus destratifying the layers of warm air. As a result, the warm air is circulated
where it is needed, and the heating system does not overwork to warm the room.
To properly destratify a warmed room, the ceiling fan should be run in a clockwise direction.
This pushes the air up against the ceilings and down the walls, to gently recirculate the
warm air without creating a cooling windchill effect.