How to Install a Retrofit Bathroom Vent Fan

We’re back with another Pro-Follow update for the bathroom remodel with Steve Wartman and his crew. If you’re just joining us, you can read up on the progress so far at these links:

Day 1: Demolition
Day 2: Plumbing, Electric and Concrete Board

In the introduction to this project, I mentioned that moving the bathroom fan was part of the plan. The original fan was situated on the opposite side of the shower and vented into the attic space. Steve wanted to relocate the fan so that it more effectively pulls moisture from the room, and he wanted to vent it out through a nearby soffit.


When the electrician came through on Day 2, he was able to reroute the electric from the original fan to the new location without pulling any new wires. This was really fortunate because that meant the wall switch was all ready to go.

If that had not been the case, the electrician would have needed to fish a new cable (14/2 NM-B) from the switch to the new fan and either run a new circuit or (more likely) extend an existing circuit.


Bathroom fan kit (fan, ductwork connections, soffit cover, fan cover)
4″ flexible ductwork (see below)
Aluminum tape
Wire connector and wire nuts

Flexible Ductwork

Flex duct is an acceptable choice for this project. However, rigid duct is an even better choice because it improves air flow. Opt for rigid duct when possible.


Drywall saw
Drill / driver
Hole saw
Utility knife
Wire strippers

Step 1: Cut the Hole

The guys provided the general location for the electrician to pull the wires. To install the fan, they needed to enlarge the hole, and they wanted the final location adjacent to a stud for mounting the fan.

After measuring the fan, they marked lines and cut out the drywall.

Step 2: Trim Duct to Length

The guys ran 4″ flexible duct between the fan and the soffit, cutting it to length.

Pro-Tip: Cut the ductwork only as long as needed. While leaving extra length may help during the installation, your bathroom fan will have to work harder to move air through.

The bathroom fan kit includes a coupler between the fan and the ductwork, and they secured the ductwork with aluminum tape.

Step 3: Run the Ductwork

Fortunately, the soffit is a short distant away, and after shifting a little insulation, they can push the ductwork through. Had that not been the case, they would have needed to go into the attic to run the ductwork.

Pro-Tip: Run the ductwork as straight as possible to avoid restricting air flow.

Pro-Tip: It’s best to run bathroom vent ductwork through conditioned space to prevent the moisture-rich air from condensing inside the ductwork.

Step 4: Make the Soffit Connection and Install the Cover

This bathroom vent kit includes a soffit cover with slats that open as the air is forced out.

Using a hole saw, they cut a 4″ hole through the soffit.

Pulling the ductwork to the opening, they secured it in place with a combination of plastic clips (included in the kit) and aluminum tape.

Next, they screwed the soffit cover in place.

Step 5: Wire Bathroom Fan

One corner of the fan features a removable plate with a knock-out, and behind that plate are the hot and neutral wires.

After removing the knock-out, Steve’s crew pushed a plastic wire connector in place and fed the wires through.

They connected the bare copper wire to the ground screw, and they paired the black wires together and the white wires together.

With all the connections made, they screwed the metal plate back in place.

Step 6: Mount the Fan

After making the hole a little bit larger, Steve’s crew pushed the fan into place alongside the stud. This fan included a few metal fins to help hold it in place, and the guys drove screws into the adjacent stud.

Step 7: Install Fan Cover

The last step for this install was to hang the fan cover which is secured with a pair of metal hooks.


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