Installing A Whole-House Attic Fan

by Darwin Hall

whole-house fan diagram

Two people can install a whole-house attic fan fairly easily.

The fan will increase the comfort level throughout your house, satisfy all your cooling needs on many days, and give your air conditioner a boost when the days are especially hot.

Unlike a ceiling fan, which only circulates air within the house, a whole-house fan requires that the attic and house be open to each other in order to ventilate.

An attic fan on the other hand, ventilates only the attic.

It is not intended as a substitute for roof vents, but it does enhance the vents ability to release pent-up heat from the attic.

Whole-House Fan Locations

There are basically two types of installation.  One consists of a fan mounted in the gable of an attic, and the other is a whole-house fan mounted in the ceiling.  To use any of these installations, you must have two air passages — one from the living space to the fan and another from the fan to the outside.

Fans are usually 24 inches, 30 inches, or 36 inches in diameter and, when in position, should have at least 2 to 3 inches of clearance above them.  Be sure to follow the manufacturer’s instructions.

whole house fanA fan draws air from all parts of the house.  Some doors or windows must be open before you turn on your fan, or pilot lights may go out and the air flow may draw soot from your chimney.

If the fan is in a spot where children or animals could reach it, be sure to put a barrier or safety cage around the fan.

Before you begin work, make sure you have complete instructions from the manufacturer.

In most cases you will have to run a separate electrical circuit for the fan; check with your local building department.

Each fan style requires its own method of installation.  The steps described here are common for most installations, however:

Installing A Whole-House Fan

1.  Cut an opening in the ceiling the same size as the fan shutter.  If the attic is insulated, use plastic sheeting or pieces of plywood to make baffles to hold the insulation back.

If the insulation is loose-fill, check with the manufacturer about the advisability of installing the fan.

2.  Cut sections out of the ceiling joists where the fan will fit.  Cut joists so there will be 1 ½ inches of clearance around the opening.

3.  Support the cut joists with headers between the full-length joists.  Double up any headers that span more than 4 feet.  Frame the other two sides of the opening by installing blocking between the headers.

4.  Build a platform of 1 by 6s to fit over the platform.  Miter the corners so that the available framing will support the platform.

5.  Set the fan in place, toenailing through the fame to secure it.  Then run wiring for the fan.  If you use non-metallic cable, run the cable through the holes drilled in the centers of the joists or staple cable beside the joists.  If you run cable over the tops of the joists, nail 1 by 4s next to the cable to form a shield.

6.  Install the shutter from below, driving wood screws through the ceiling into the frame.

Watch the VideoFor allergy sufferers, adding a whole house fan can be a God-send.  It increases your home’s coolness without running your air conditioner.  The cost is recouped through power savings and a comfortable living area, flush with fresh air from outside.

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