By Gene and Katie Hamilton
Before You Begin
These instructions are for installing a basic attic fan. If you want more options to control the fan, consider hiring an electrician because additional wiring is needed. There are two-speed units and a speed control switch that lets you determine the volume of air you want to move along with the volume of sound the unit creates while it is operating. You can regulate it with a thermostat switch that turns it on and off at preset levels. Some units have high-temperature sensors that automatically shut down to prevent heat overload or a possible fire.
Check with your local building department to see if a permit and inspection is required for a whole house fan.
A whole house fan is not a good choice in an attic with loose, uncovered or blown-in insulation because of the strong air movement it creates. Another drawback concerns the quality of outside air it brings indoors. Fresh air may be natural, but as the unit draws in all that outside air it also invites in pollen, dust, humidity and other nuisances, not good for anyone who suffers from asthma or hay-fever.
Step 1 : Position the fan
Choose a central location, such as a hallway where the opening won't be prominently visible. Position it directly over a ceiling joist, with the louver panel located directly underneath it. In the attic, the top of the fan should be at least 20 inches below the roof rafters, and away from any obstructions like walls or doors. The fan requires a minimum of 1 sq. ft. of vent area in the attic for each 750 CFM it delivers. A CFM means the cubic feet of air that a fan can move per minute. In a 1,500 sq. ft. house this equals a total of 6 sq. ft. of net-free vent opening in the attic.
Step 2 : Lay out the cut
Mark your chosen location on the ceiling and drill a small center hole through the drywall. Poke a wire up through this hole, then go into the attic to see if your location suits the joist layout. Clear away all of the insulation between the joists where you will be working, and lay down plywood or boards to provide a safe platform for yourself and your materials.
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