How To Install a Quiet Bathroom Fan (page 3 of 3)

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Tips and Buyer's Guide

TIP
To simplify cutting, line up two sides with the existing hole. Wear goggles while cutting.

Before going back into the attic, cut a piece of insulated flexible duct approximately 18 to 24 in. longer than the old duct and cut one piece of 4-in. dia. aluminum ductwork 6 in. long. Take them into the attic along with the fan, fan mounting brackets, aluminum elbow, sheet metal screws, drywall screws, electrical cable staples, electrical clamp, caulk and duct clamps. You may also need blocking to attach to the joists to support your new fan housing.

You’ll need a helper to mount the new fan. Slide the mounting brackets on and extend them to the joists. Align the fan with the new drywall hole. Then ease it down to your helper, who will hold the housing flush to the ceiling while you screw the brackets to the joists.

Run Your Insulated Duct Like the Pros Do
After installing the fan, run the ducts. Attach the aluminum elbow to the exhaust port and the duct liner to the elbow. Then measure and cut the flexible insulated duct. The ideal duct run should be as direct as possible, with the fewest turns. Extend the duct from the exhaust port to the roof opening, but don’t stretch it so tight that it kinks. Then finish connecting the insulated duct to both aluminum ends.

With our fan, the wiring is done from the attic. Some models wire from below. In either case, clamp the electrical cable to the housing with a standard clamp with 6 in. of wire extending into the box. Strip 5/8 in. of insulation off the end of each wire and connect the wires. Staple the cable to a framing member within 12 in. of the cable clamp.

You may find that the existing electrical cable is too short to reach the new fan. If the cable runs to a nearby junction box, you can replace it with a longer section. Otherwise, you’ll have to install a new junction box. If you’re not familiar with the rules of wiring, call in a licensed electrician to do this part. In any case, have your work checked by the local electrical inspector.

Seal the perimeter of the fan housing with flexible caulk. This is critical for reducing sound transmission as well as air leakage. Replace the insulation, making sure to cover the fan housing.

TIP
Look around for all your tools before you go back down!

Complete the Roof Work in One Trip
While working on the roof, you’ll need the new roof vent cap, a scrap of the straight aluminum ductwork (cut one end to match the roof angle), a jigsaw, a tape measure, roof cement, caulk, a utility knife, roof nails, 1/2-in. Phillips self-tapping sheet metal screws, metal snips, a pry bar, a carpenter’s pencil and a hammer. Wear a tool belt or apron or you’ll be going up and down the ladder retrieving stuff that slides off!

If you’re not fully confident working on your roof, install a pair of roof brackets along with a 2x10, or nail a 2x4 cleat to the roof a few feet below the vent opening. It’ll give you a more secure area to place your feet as you work on the roof.

Replace the old vent cap with a new one. Remove the old one carefully so you don’t damage shingles. They can be brittle, especially on a cold day. Then enlarge the old 3-in. hole to fit the 4-in. duct, using the 4-in. duct as a template. The opening will be oval-shaped in the direction of the roof slope.

Reach through the roof and pull the straight aluminum duct up through the hole, with the angled end extending 3/4 in. above the roof surface. Screw the duct to the sheathing. A magnetic drill bit is helpful here.

TIP
Drive a roofing nail through the side of the duct to temporarily anchor it.

Seal around the edge with caulk to keep condensation from running back down the duct or under the shingles.

Check the screen and the damper in the new vent cap before installing it to make sure both are in place.

When you’re done, fill any nail holes you put in the roof with roofing cement.

Your Reward . . . Silence
To complete the job, install the decorative grille. Now is the moment of truth. Turn the power back on and listen to the fan—if you can hear it!

Shopping for a Quiet Fan

A quiet fan has a “sone” rating between .5 and 1.5. A sone is a measure of loudness. The lower the number, the quieter the fan. By contrast, typical low-cost bath fans range from 2 to more than 5 sones (which you can easily hear in the next room).

Select the ventilation capacity of the fan that fits the size of your bathroom. To quickly estimate the cfm needed (cubic feet per minute, or how much air a fan moves), a “rule of thumb” is to multiply the length of your bathroom by the width and round up. For example, an 8 x 10-ft. (80 sq. ft.) room would need a vent rate of 80 cfm and would require an 80-cfm fan.

Quiet fans have better motors (rated for continuous operation), heavier-duty housings and larger ducts, usually 4 in. They cost considerably more than standard fans. The cost for exhaust fans in the .5 to 1.5 sone range, at a home center or a heating equipment supplier, is $80 to $100.

To contact manufacturers, see below.