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How to Replace a Bathroom Exhaust Fan: Step-by-Step

Keep on top of moisture by replacing your bathroom exhaust fan.

You don’t always notice when your old bathroom exhaust fan starts to fail. If it’s getting noisy, or you see your bathroom mirror misting up more frequently, it may be time to swap it for a more efficient model. But not everyone knows how to replace a bathroom exhaust fan.

We guide you through how to install a bathroom exhaust fan in a few simple steps.

Key Takeaways

  • Choose the right fan size based on the bathroom’s square footage and required CFM (Cubic Feet per Minute) for proper airflow.
  • Plan the exhaust route through either a roof or gable wall to ensure proper outside ventilation and avoid moisture buildup in the attic.
  • Consult a qualified electrician to determine if you need a permit for the electrical installation and to ensure it complies with regulations.
  • Turn off the power before removing the old fan, then follow a step-by-step guide to install the new bathroom exhaust fan correctly and safely.

Can I Replace a Bathroom Exhaust Fan Myself?

It is possible to replace the fan yourself, but you should consult a qualified electrician to determine if you need a permit for the electrical installation. Most local government units (LGUs) will insist that an electrician inspect your handiwork to check it complies with regulations.

You should factor in the cost of the electrician as this will increase your expenses. Expect to pay an amount that is dependent on the type of inspection required.

You can find out the requirements by speaking to your LGU in advance of the installation.

Plan Ahead

Replacing your bathroom exhaust fan takes planning. You need to determine several important factors.

Determine the Fan Size

Replacing like for like is the easiest way to swap a fan because you don’t have to make a larger hole in your ceiling. But you might want to upgrade, and for this, you will need to make adjustments.

An exhaust fan is required to exchange the air in the bathroom at least 5 times every hour, so make sure you pay attention to the CFM.

Fans are rated in CFM, or Cubic Feet per Minute, which is a measure of airflow. The size of your bathroom determines the CFM values of your fan. Bathroom fan sizing is typically based on square footage.

Some manufacturers work on the calculation below:

Length x Height x Width x 0.13 = the number of CFM rounded to the nearest 10.

Smaller bathrooms require about 50 CFM, while for larger rooms over 100 square feet, you need to factor in the increased CFM for each of the following:

  • Toilet: 50 CFM.
  • Shower: 50 CFM.
  • Bathtub: 50 CFM.
  • Jet tub: 100 CFM.

Determine the Exhaust Route

The fan can vent through either a roof or gable wall because you will need outside ventilation. If you allow the bathroom fan to vent into the attic, you will increase the moisture content inside your home and potentially rot the rafters.

Avoid soffit and ridge vents because the steam will re-enter the attic through the vents. When you are ducting through the roof, be aware that you need to use the correct sealant to stop water from getting in.

Determine Your Electrical Options

It’s always best to utilize the existing switches of your old fan, but that may not always be possible. Some fans have lights, which operate from a double switch. If your old fan doesn’t have a light, you will need to upgrade the wiring.

What You Need

  • Power drill.
  • Voltage tester.
  • Screwdriver.
  • Safety goggles.
  • Safety gloves.
  • Wooden plank.
  • Light.
  • Metal snips.
  • Wire cutters.
  • Utility knife.
  • Wire stripper.
  • Jigsaw.
  • HVAC tape.
  • Pencil.
  • Roofing cement (if going through the roof).
  • Replacement tiles (if going through tiles).

How To Replace and Install a Bathroom Exhaust Fan

1. Turn Off the Power

Turn off the power at the mains. Loosen fuses and flip circuit breakers while the fan is still running. Put on your safety goggles to protect your eyes from falling ceiling dust.

2. Remove the Motor

Remove the old grille cover and discard it. Using a screwdriver, unscrew the fan assembly and remove it.

Protect your hands from sharp edges by wearing gloves. Use a voltage tester to make sure the power is off. The connections are housed in a small splice box. Disconnect them using the wire cutters and remove the motor.

3. Get Into the Attic

Take your power drill into the attic, along with your wire stripper, utility knife, screwdriver, light, metal snips, and wire cutter. You might also need a small flat length of wood about 2 ft x 3 ft to make it easier to work in the attic.

Push the insulation away from the spot where you need to work to reveal the old fan housing. Use the power drill to loosen tight screws, especially if they are attached to a joist.

If you don’t have access in the attic to the housing, you’ll have to cut it out from below using a jigsaw. This creates damage to your ceiling, but you cannot avoid it.

Top Tip

Watch out for aluminum wiring as this requires a qualified professional to remove.

4. Disconnect the Wiring

Move the housing around the hole to get access to the electrical cables. Disconnect any additional wires and pull them out of the fan housing. Remove the exhaust duct from the fan, as well as the housing from the ceiling.

5. Check the Size of the New Fan

Hold the new fan up to the hole and see if it fits. If not, you will need to extend the gap. Use the new fan as a template and draw around it with a pencil. Then make the cuts with your jigsaw. If you don’t have a jigsaw, a small hand saw will do.

6. Adjust the Hole

It might be a case of trial and error when it comes to getting the sizing right. If the hole is too big, patch it with strips of drywall. You can screw the drywall into the ceiling joists to keep it in place.

Don’t worry too much about the neatness because you can hide it later during the touch-up stages.

7. Attach the Duct Connectors

Secure the duct connector to the fan housing by sliding it into the pre-existing slots. If you need to strip away some wire insulation, use the wire strippers.

8. Back Into the Attic

It’s time to secure the housing brackets by screwing them to ceiling joists, which are typically 16 to 24 inches apart. Remember to take your wooden plank to give you a secure platform to work from.

Insert the brackets into the housing slots and then screw the brackets to the joists, making sure the fan sits evenly and flush in the ceiling below.

9. Prepare To Connect the Wiring

Take off the wiring cover from the housing, as well as the knockout plug, using a screwdriver. If the screws are stuck solid, use the power drill.

10. Connect the Wires

Feed the wires through the clamps and tighten the screws. Connect the fan wires to the house wires using quick connectors. Make sure you match the colors. Green is the ground and connects directly to the green wire. The neutral white wire joins to the corresponding color, and the black attaches to the black.

You can use traditional connectors by attaching the bare wire ends together and twist the connector clockwise.


Don’t cover the connectors with electrical tape unless you are required to do so by local codes.

11. Replace the Wires

Push the wires into the housing and secure the wiring cover to the housing with screws.

12. Connect the Duct

Using HVAC tape, secure the 4-inch duct to the duct connector. The duct should vent to the outside.

13. Check the Fan

Turn the power back on, and listen carefully to see if the fan is working. Some bathroom fans are very quiet. The grille secures via springs that slot into the housing and clip into place.

14. Touch-Up Time

Now you can touch up the ceiling around the grille using spackling compound and ceiling paint.

Top Tip

Repaint the entire ceiling as old and new paint may not match exactly.

Tips for Replacing a Bathroom Exhaust Fan

When it comes to replacing your ceiling exhaust fan, there are easy ways to do it, including hacks and cheats. Here are some top tips.

Buy Like for Like

This is the most obvious tip because swapping two identical exhaust fans makes life so much easier. The dimensions are the same, the electrics match, and the ducting should slot right in. Once you start upscaling the hole or changing the layout of the venting system, it creates a whole heap of challenges.

Follow the Moisture

Position your exhaust fan nearer to the moisture source. If that’s the bathtub or shower, place the exhaust fan as close as possible, making sure you don’t get too close to the water because of electrics.

Drill a Locator Hole

If you are fitting a fan for the first time, drilling a locator hole in the ceiling tells you if you have the correct spot. The last thing you want is for the hole to get cut beneath a ceiling joist.

Check the Attic First

It’s always a good idea to poke around in the attic before starting the installation. Getting to know the layout of the joists and where the existing fan is located will help with your understanding.

It also helps you decide on the best duct layout.

Don’t Guess It

If you are unsure about something, especially the electrical installation, don’t make it up as you go along. It could lead to injury or a fire. Call in the professional, so it gets done properly the first time.


How Much Does It Cost To Replace a Bathroom Exhaust Fan?

Typically, it costs between $239 and $540 to install a bathroom exhaust fan. The national average comes in at $374. Still, this figure could be more or less depending on the fan quality, your location, and whether you get a professional to do the installation.

How Long Does a Bathroom Fan Last?

A bathroom exhaust fan lasts about 10 years. You can extend its life with regular cleaning and maintenance, but eventually, the motor will burn out.

What Causes a Bathroom Fan To Stop Working?

Your fan might have stopped working because the motor has burned out, or there is no power to the fan. Check the main circuit breaker to see if the power is working. If not, you will need a new fan.

Can You Replace a Bathroom Fan Motor?

The short answer is, yes, you can. Some LGUs issue different instructions regarding permits, with most requiring the electrical side of the installation to be inspected and signed off by a qualified electrician.

It should take you about a day to do, and it is a medium-skill task.

How Do I Know What Size Bathroom Exhaust Fan I Need?

To determine the best size exhaust fan, you need to calculate the volume of your bathroom. Multiplying the length and width of your bathroom will give you the square footage.

The standard unit of measurement for airflow is the cubic foot per minute (CFM). A standard-sized fan is sufficient to ventilate a bathroom of 100 square feet or less. You should aim for at least 1 CFM per square foot of floor space.

What Is a Ductless Bathroom Exhaust Fan?

As the name implies, a ductless bathroom exhaust fan is a model that doesn’t need a duct to function. Air is filtered to eliminate moisture, smells, and contaminants, then recycled into the room.

Installing a conventional bathroom exhaust fan may not always be viable, which is why ductless bathroom exhaust fans have become increasingly popular in recent years.

Installing a duct for an exhaust fan, for instance, may be challenging or even impossible in some older residences or in structures with concrete.

How Do I Know If My Bathroom Fan Vent Is Clogged?

Putting a single square of toilet paper or a Kleenex down the edge of the fan while it’s operating is the quickest and most convenient way to determine whether or not the van has adequate ventilation.

It functions correctly if the fan can maintain the paper attached to itself while still holding it up.

Can You Install a Bathroom Fan Without Venting Outside?

You can definitely install a bathroom fan without outside venting, but exterior venting is the best solution in almost every case. If it’s not possible for you, there are a few alternatives.

These situations usually call for the usage of a ductless bathroom fan. They include a special filter that draws in air from the room, traps any moisture or odors, and then sends that air back into the room.

Even though they aren’t as efficient as vented fans, exhaust fans can increase air circulation and decrease the likelihood of mold and mildew growth inside.

Do I Need an Electrician to Install a Bathroom Exhaust Fan?

You generally need an electrician to install a bathroom exhaust fan.

The installation of a new fan will necessitate the running of new wires, and it is recommended that homeowners avoid attempting any electrical work themselves for their own safety and the protection of their property.

These days, most bathroom exhaust fans also function as lights, so you can clear the air and brighten the space without sacrificing either. Call an electrician if you need a new bathroom exhaust fan installed or an existing one replaced.

What Is the Difference Between a Bathroom Exhaust Fan and a Ventilation Fan?

Its purpose is the main difference between a bathroom exhaust fan and a ventilation fan. A ventilation fan will bring fresh air into the bathroom, while an exhaust fan will eliminate moisture and nasty odors.

Both of these fans draw in the fresh air, but while one does so to increase ventilation, the other serves to filter out potentially dangerous particles from the air inside.

It’s Not Exhausting

Fitting a replacement bathroom exhaust fan needn’t be a chore. All it takes is planning and patience. Try and use the most straightforward venting layouts and try and work with an identical fan to match the electrics and dimensions.

Finally, don’t be afraid to admit defeat and call in the professionals if you get stuck. Why risk it?

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About the Author

Mark Weir

Mark spent 24 years working in real estate, so he knows his way around a home. He also worked with contractors and experts, advising them on issues of planning, investments, and renovations. Mark is no stranger to hands-on experience, having renovated his own home and many properties for resale. He likes nothing better than seeing a project through to completion.