Replacing a Bathroom Exhaust Fan

In this video, you’ll learn the importance of exhaust fans in the bathroom.  It is brought to you by Mike from Lowe’s.  He goes over all aspects on what you need to consider before making your purchase.  You can’t just go out and buy any exhaust fan.  You’ll need to know how large your room is especially how high the ceiling.  After you’ve made your purchase and are ready to get started, any time working with electricity, remember to turn off the power supply for safety.  I recommend watching the video or reading it here before getting started.  You may also want a helper standing by just in case.  In my powder bath, it was installed with the exhaust fan and light combo.  I don’t recommend it as I think it is too loud.  I might have to take these things into consideration and shop for a new exhaust fan myself.


Moisture in the bathroom is to be expected but too much moisture can lead to problems like mold.  That’s why it’s important to have a good working exhaust fan.  Today’s fans are more efficient and quieter than those of the past.  So if your fan is old, noisy or just doesn’t work well, it’s time to replace it.

Modern exhaust fans come in many different styles.  There’s fans with heaters, fans with night lights and fans with humidity-sensing controls for hands-free operation.

We’re installing a fan with a decorative light, but before you head out to buy one, you need to understand a little fan science.  Bathroom fans are rated in sones and CFM.  Sones are a measurement of the sound level, so the lower the sone number, the quieter the fan.  A 2.5 or lower is considered quiet.  Fans are also rated by air flow in cubic feet per minute or CFM.  To determine the minimum CFM you’ll need, multiple the bathroom length x the width to get the square footage.  Then for an 8-foot ceiling, multiple the square footage by 1.1.  For a 9 to 12 foot ceiling, multiple by 1.25, and for a cathedral ceiling, multiple by 1.5.  Just check the package to find the fan that’s right for your bathroom.

This project isn’t too difficult but if you’re unsure about working with electricity, contact an electrician for help.

Now the installation for different fans will vary so be sure to read the manufacturer’s instructions for your fan.  The printable instructions and the tools and materials for this project can be found at

Here’s what we’ll need for our project: A new exhaust fan, Phillips and standard screwdrivers, a drill with bits, pliers, a keyhole saw or reciprocating saw to cut the wallboard, wallboard repair supplies and a dust mask.  Duct tape, electrical tape and masking tape, a circuit tester, wire connectors if not included with the fan, wire strippers, a utility knife, pencil and marker, a work light, drop cloth and safety glasses.  You might also need a small piece of plywood if working in an attic.

To start, our manufacturer recommends disassembling the new fan to remove the packing and get it ready for installation.  It’s a good idea to prep the bathroom, so cover the work area with a drop cloth.  Then turn off the power to the fan at the main electrical box.  Take off the grill and use a circuit tester to make sure the power is off.  To remove our old fan, we start by taking out the motor, then the mounting screws.  With the housing free, we can slide it to one side to disconnect the vent duct.  We lower the housing through the hole.  That gives us access to the wires but before we disconnect them, we mark which ones are connected to the light and to the fan.  Finally, we disconnect the wiring.

If you can access your old fan from the attic, consider doing the removal up there.  A small piece of plywood will help you kneel on the joists.  Now if your new fan is smaller than your old one, you’ll have to make some adjustments to the ceiling.  To see how, check the printable instructions for this project at If your new fan is slightly larger than the old one, just set the fan against the old hole, mark around it and then cut the opening.  Don’t forget your safety glasses.

Now it’s time to mount the fan in the ceiling.  But before you secure it, slide it to one side and mount the wires in the stream relief hole.  Then tighten the clamp.  Then slide the housing to the other side and connect the duct with duct tape.   Some units might need an adapter.  Now we can secure the fan.  Position it so the bottom of the housing is flush with the ceiling.  Then guide the screws into the ceiling joist.  All secure.

Now, the wiring isn’t as difficult as you might think.  First connect the ground and neutral from the fan to the ground and neutral from the house with wire connectors and electrical tape.  There are two ways the wiring can be configured.

If you have a fan with a light on separate switches, connect the black wire from the fan to the wire from the house labeled fan.  Then connect the black wire from the light to the wire labeled light.  If your light and fan are on the same switch, then just connect both black wires from the fan and light to the single house wire.  With everything connected, install the wiring cover.  Then connect the motor wires.

Position the motor back inside the housing, making sure you don’t damage the wires.  Secure the motor with the included screws.  Before you attach the light, turn on the power to see if the fan works.  If not, turn off the power and use a circuit tester to make sure the power is off at the fan before checking the wiring.

When the fan is working, install the light and grill.  Remove the mounting nuts from the motor.  Then connect the wiring harness to the cover plate.  Slide the lid in place and replace the nuts.  Install two light bulbs, line up the glass dome and rotate into place.

Remember to clean your new fan on a regular basis with a vacuum cleaner.
And now our bathroom is updated with a new exhaust fan and light.  It’s quieter, more efficient and stylish all at once.

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