Whole-house fans are an economical, energy-efficient
alternative to air-conditioning. In some regions, it may be the
only cooling mechanism you need; in others, it can shorten the
length of time you need to run your air conditioner and save
hundreds of dollars annually.
Capacity. Whole-house fans come in different sizes
to accommodate different attic construction and house sizes.
Increase the convenience by installing a timer or thermostat.
Fans are sold according to their cubic feet per minute (CFM)
capacity, which indicates how much air they move. Depending on
the climate, you need a fan that will change the air in your
house every two to three minutes. To determine the CFM requirement,
take the total above- ground square footage and multiply it by
three for moderate climates or four for warmer climates.
Location. For this type of fan to work effectively,
install it in a central location on the upper level of the house;
usually the hallway that leads to the bedrooms. Check for obstructions
in the attic after you’ve determined the best location. In cold
climates, make certain the units can be tightly sealed and insulated
during heating season.
Operation. Use a whole-house fan only when the outside
temperature is cooler than the inside temperature. To use it,
shut off the air-conditioning and , in the rooms you want cooled,
open the windows about 2 to 3 in. (5 to 7.5 cm) and block open
Caution: Don’t use the fan when windows
are closed. This will cause interior air to be exhausted without
being replaced with fresh outside air. When this happens, back-drafting
can occur, which means deadly carbon monoxide fumes given off
by water heaters and other gas-burning appliances may be drawn
into your home rather than exhausted through their venting systems.
Above: How attic fans cool. Attic fans cool by pulling
cooler, outside air in through windows that are open by 2 to 3
in. (5 to 7.5 cm) and drawing the warm air in the house up into
the attic. The warm air in the attic then exhausts under pressure
through vents in the roof.
1. Locate center ceiling joist for fan location and cut out a
slot on either side. Align and position template on center
ceiling joist and , after checking for obstructions, cut completely
around outer edge. Remove drywall.
2. Position the fan by placing its motor over the center ceiling
joist with fan edges aligned with the drywall cutout. Place plywood
or lumber across joists for a comfortable work platform.
3. Mount the switch box to the ceiling joist. Run cable from
a new circuit or nearby power source and make connections. The
switch box may contain a pull chain for operation or you can
install a wall switch.
4. Secure saddle brackets to the center ceiling joist with nuts and bolts. Make sure the fan is centered before you drill holes
in the joist.
5. Fill the gap between the ceiling and fan frame with cardboard
baffles; some manufacturers supply them. Cut baffles to fit between
ceiling joists and screw the baffles to the fan frame. Cut insulation
to fit up to the baffles.
6. Attach the louver panel to the ceiling with screws into the
joist and drywall anchors into the drywall. Louvers are drawn
upward when fan is turned on and weighted to shut tightly when
the fan is off.