How to Install a Bathroom Fan With a Roof Vent in the Ceiling: The Ultimate Guide

Josh Miller

Josh is a contributing writer to the site and former HVAC specialist.

Last Updated on January 30, 2022

A bathroom fan is one of the essential elements of a home’s ventilation system. Removing moisture, odors, and heat from your bathroom, a high-quality bathroom fan is critical for ensuring a well-ventilated and hygienic space.

So, whether your existing ceiling fan is coming to the end of its working life, or you’re looking to introduce one into your bathroom, dive into the ultimate guide on how to install a bathroom fan in the ceiling. Though it can seem overwhelming, it really doesn’t take a pro to get this job done. With step-by-step instructions for installing a bathroom fan with a roof vent, you’ll be able to enjoy the ventilation benefits your fan has to offer in no time.

Step-by-Step Guide to Installing Bathroom Fans

Step 1: Cut the Hole in Your Ceiling

When it comes to installing your new bathroom ceiling fan, the first thing you’ll need to identify is what size hole you need to cut in relation to the size of the fan. To give you a better idea of what size is best for you, refer to this breakdown of dimensions:

For bathrooms, 79 sq ft. and smaller, small bath fans provide sufficient ventilation.
For bathrooms 80-100 sq ft. in size, medium bath fans work adequately.
For bathrooms 100 sq ft. and larger, you’ll need to use either a large or exhaust fan to ensure the air circulates properly.
If you have a bathroom with separate rooms for the shower and toilet, you may need to think about adding additional fans to cover both areas.

To cut the hole in the ceiling, you will need to:

Mark the location of your bathroom fan. Do this by implanting a roofing nail of 16” into the drywall at each corner, ensuring the nails poke out into the attic.
Head to the attic and locate the nails, marking where the fan will be placed with a marker.
Using either a reciprocating saw or a drywall saw, cut out the plaster or drywall. Ensure you begin the cutting process by drilling a hole in the drywall that is large enough to take on the saw blade.
If you don’t have an attic, or it is inaccessible to you, you can use a stud laser to locate a joist from your bathroom.
In this instance, cut the fan opening from below and use the system’s enclosure as a guide.

Step 2: Attach the Fan

The next step in this process requires attaching the fan enclosure to the joist. This attachment needs to be done using screws.

Either push or cut back the insulation. Ensure you leave a 6” gap between the insulation and the unit itself.
Source or cut a 2 ft. x 4 ft. wooden board and fit it between the joists. This blocks the fan from the insulation.
Using screws, attach the wood pieces securely in place.

Step 3: Cut a Hole in Your Roof and Remove the Shingles

This step requires optimum caution, and you should only perform it if you are wearing protective safety equipment, especially a hard hat. Exercise extreme caution when climbing up and down your roof: always use a secure ladder and ensure someone is standing by at all times.

On the underside of your roof, draw a small circle. Ensure it is the right size for the tailpipe and roof vent.
Next, drill a large enough hole for the saw blade, and cut out the circle with either a reciprocating saw or a saber saw.
Ensuring you take extra care not to damage the underlying roof paper, remove the roof shingles from the surrounding cutoff area.

Step 4: Install Your Roof Vent

Begin this process by sliding the top flange from underneath the shingles above it, ensuring the bottom flange is rested on the shingles below.
Apply roof adhesive to the underside of each flange and seal.
Use roof nails to fasten the vent flanges before you reinstall the shingles.
Reinstall the shingles on each side of your roof and use roofing cement to secure the shingles with the joints.
Lastly, place the last shingle beneath the existing shingles that are above the vent.

Step 5: Connect and Wire Your Fan

Begin by sliding some clamps over the flexible duct at both the fan housing and roof cap.
Next, slip the clamps over the tailpieces of the fan and roof vent, ensuring you tighten the clamps securely.
Using duct tape, wrap and secure the joints.

Before you begin any wiring, turn off the power at your circuit breaker box. To ensure it is safe to proceed to the next steps, you’ll need to:

Run the cable to your fan and switch if no wiring has previously been installed.
If your fan has a light, you’ll need to run a three-wire cable from the switch to the fan.
Connect the wiring according to the manufacturer’s instructions.
Plug in the fan motor to the built-in receptacle.

Step 6: Wire the Fan

If your fan light switch already has existing wiring, intertwine the white wires and connect the grounds tightly with high-quality wire connectors.
Next, connect the power source to both switches.
You’ll need to connect the red wire to one switch terminal and the black wire to the other
To turn on and operate your bathroom fan, be sure to follow your specific manufacturer’s instructions.

Enjoy a Well-Ventilated Bathroom With Your Newly Installed Fan

Learning how to install a bathroom fan independently isn’t as challenging as it seems. With the proper instructions, you’ll be able to enjoy a well-ventilated bathroom in no time. However, it’s always wise to draft in professionals for steps out of your comfort zone, as you don’t want to compromise the fan’s function or your safety.

From reducing moisture to decreasing the risk of mold and an unsanitary environment, a well-installed fan system provides you with lasting benefits in the bathroom. So, what are you waiting for? Install your bathroom ceiling fan now and enjoy years of clean, fresh air and optimum hygiene.

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