How to Install a Whole House Fan

This Old House general contractor Tom Silva shows how to install a whole house fan.

Steps for Installing a Whole House Fan

1. From inside the attic, take up any plywood floor covering the desired fan location.
2. Lift out the insulation from between the ceiling joists.
3. Cut two pieces of 2×10 to fit snugly between the ceiling joists. Set the blocks slightly farther apart than the length of the whole-house fan. Nail the blocking in place with 16d nails.
4. Replace the plywood floor, fastening it to the joists with 1 5/8-inch drywall screws.
5. Use a plunge router fitted with flush-cutting bit and guide bushing to cut out the plywood floor.
6. Cut through the ceiling with a reciprocating saw, making sure someone stands below with a wet/dry vacuum to catch the dust.
7. Fill the gap between the ceiling hole and attic insulation with spray-foam insulation. After the foam hardens, trim away the excess with a utility knife.
8. Apply self-stick weatherstripping around the underside of the flange on the whole-house fan.
9. Set the fan down into the hole, pressing it tight against the plywood attic floor.
10. Secure the fan by driving 1 5/8-inch screws through its flange and into plywood floor.
11. Attach the fan’s grille from below.
12. Plug the fan into a nearby outlet; if necessary, hire a licensed electrician to install an outlet close to the fan.
13. Open the downstairs windows and any attic windows.
14. Use the remote control to turn on the fan.

Materials

• 5/8-inch drywall screws
• Weatherstripping
• Spray foam insulation

Tools