Home and Garden | Install Whole-House Fan - Heating

You can add a whole-house fan to your home in a weekend if you have basic do-it-yourself skills and a helper's assistance.

Once you've chosen your fan, pick out a place for it where it can draw air from all parts of your home and release it through vents in your roof. A central hallway is the best place to situate a whole-house fan, at the highest level of the house. If possible, pick a spot away from the bedrooms so fan noise won't disturb sleepers.

TOOLS & MATERIALS

Drill-bit set	Whole-house fan
Cordless drill/driver	Masking tape
Reciprocating saw	2-by lumber (sized to match joists)
Handsaw	1-by-4 lumber
Wallboard saw	8d and 12d nails
Framing hammer	Drywall screws
Screwdriver	3/4-inch adhesive-back sponge rubber
Socket wrench	12-gauge NM wire
Fish tape	12-gauge NM wire
Long-nose pliers	Electrical box
Dust mask	Towel or clothes hanger
Try Square

INSTRUCTIONS

Placement and installation
First rule of thumb: Make sure there's at least 3 feet of clearance above the fan when it's installed in the attic floor. Otherwise, there may be too much air resistance for the fan to operate without straining.

Second, place the fan so that you won't need to cut into the framing, or at least so that you can minimize such cuts. Some fans are compact enough to install between ceiling joists set on 24-inch centers. Others mount on top of attic joists, with sheet metal louvers that close the opening in the ceiling when the fan is off.

Third, some of the more powerful belt-drive units are so large that you'll need to cut a joist or two and build a box as well as make an opening for the fan. If you put in this kind of fan, don't scrimp on materials: A sturdy box will minimize noise and vibration.

Installing fans that fit between joists or sit atop them is simple: You just cut an opening in the ceiling and bolt the fan to the framing. Manufacturer's instructions are pretty much all you need for these. Here, however, we'll cover the installation of a large, belt-drive fan — so you'll know what to do in the most complex situation. Installation will likely require cutting one or more joists, so be sure to consult your building department about your community's

code

requirements. You may need to use doubled framing, for example. (For the sake of clarity, our drawings show single framing timbers.) And in all cases, check with your building department for electrical code requirements: you'll be adding a switch in the wall and new circuit in your service panel. (you may want to check out our article on building codes.)

Note: Don't forget the weather. Install your fan when the temperature outside is moderate. Working in a hot attic can drain you quickly. Finally, be prepared for the mess of cutting drywall and joists. Protect the floor in your work area with a good drop cloth, and have a shop vacuum handy.

Fig. 1

1) Decide where you want the ceiling opening
You'll probably have to compromise between the ideal (which you'll mark on the ceiling) and the real (which you'll mark and cut in the attic). You'll work with the mounting template supplied with your fan, first marking its position on the ceiling, then transferring that location to the attic. If you don't have a template, make one by tracing the outline of the fan's shutter assembly onto stiff cardboard and cutting out around it.

Measure the template diagonally, from corner to corner, and mark its exact center. (This will allow you to transfer its location from ceiling to attic.) Tape the template to the ceiling in your ideal location, measuring to be sure it's centered and square with the walls in the hallway you've chosen. Drill a 1/4-inch hole through the center mark and just through the ceiling. (If you hit a joist, move the drill over an inch or two and try again.) Now push a straightened wire clothes hanger or a thin dowel through the hole and into the attic so you can find the hole from above.

2) Transfer the layout to the attic
Take the template into the attic, find your hole marker and place the template over it. If the spot you've chosen requires you to cut a number of joists or work around pipes or wiring, try shifting the template to reduce the number of obstacles. Keep in mind, though, that moving the template also shifts the opening in the ceiling below.

Clear away any insulation and debris, and with a tape measure and a try square, measure and mark all cutting lines from the template onto the drywall and joists. The box opening should be at least 1/2 inch wider than the fan housing. Otherwise, the housing may get stuck part-way down when you drop it into the box. Also, when you lay out joist cuts, be sure to allow for the offset between the ceiling cut and the cut ends of the joists, as shown below.

Choose Suitable Location and Mark Outline

Fig. 2

3) Frame the opening
Use a reciprocating saw or handsaw to cut the joists, cut through the ceiling only where you have to. Measure, cut and install the headers, ledgers and other new framing. Use a framing hammer and 8d nails to nail the headers between the joists you cut. Use three nails per joist. Then, nail box joists between the headers to create a box for the fan. Finally, use 4d nails or 1-1/2-inch drywall screws to fasten 1-by-4 ledgers to support the fan. (Some fan models use mounting brackets rather than ledgers. If yours does, you'll skip the ledgers and simply bolt the brackets to the fan assembly and then to the headers.) When the box is installed, use it as a guide to cut through the ceiling with a reciprocating saw or drywall saw. From below, fasten the cut edges of the ceiling to the box with 1-1/2-inch drywall screws.

4) Install the fan
To reduce noise and vibration, apply 3/4-inch adhesive-backed sponge rubber to the support frame. If necessary, assemble the fan parts. You'll need a screwdriver and possibly a socket wrench. Then set the fan on top of the rubber mounting strip. To keep vibration to a minimum, don't nail or screw the fan to the headers or box joists. The weight of the fan is enough to hold it in place. Check the fan-belt tension. (You can skip this step if you're installing a direct-drive fan.) The belt between the motor and fan blade should have about 1/2 inch of "give" when you press on it. If there's more slack than this, use a socket wrench to loosen the motor mount bolts, and then slide the motor away from the fan until the belt is tight. Retighten the motor mount bolts.

5) Wire the fan
Although a whole-house fan doesn't use much electricity when it's running — just the equivalent of a few lightbulbs — it draws heavy amperage when you turn it on. For this reason, it should be on its own circuit. (Here's where you may want to bring in a pro.) With the circuit in place, you can fish cable to the wall below and install a box and a switch for the fan. If there's a switch in place already, you may be able to fish along an existing cable run, install a double box and put your new switch in it. Wire the fan and switch with 12-gauge NM wire.

6) Install the shutter
The shutter assembly is screwed into the support framing from below, blocking off the fan when it's not in use and providing a neatly trimmed edge to the opening. Have a helper hold the shutter assembly against the ceiling, and mark the location of the shutter mounting holes on the ceiling. Drill pilot holes one size smaller than the screws, and then screw the assembly in place. Open a window, turn on the fan — and keep cool this summer.

Installing a Whole-House Fan