Installing a bathroom exhaust fan is important in helping to eliminate or reduce mold on your walls, as well as reduce odors.  Consider installing a bathroom exhaust fan yourself, rather than spending a lot of money on an electrician. Please be sure to visit our bathroom remodeling ideas article for other helpful hints!

Tools and Materials Needed for Installing a Bathroom Exhaust Fan

• Phillips and straight screwdrivers
• Wire strippers/cutters
• Drywall saw
• Electrical tester
• Pencil
• Electrical cable (2-wire ground NM type)
• Wire nuts
• Flexible dryer vent duct
• Soffit vent
• Exhaust fan unit

How to Choose the Best Bathroom Exhaust Fan for Your Home

The two most common types of fans are impeller fans and blower fans.  Impeller fans move air with blades that are similar to airplane propellers.  Blower fans are similar to hamster wheels, and provide better performance than impeller fans.

Choose a quiet, energy efficient fan in the size range required.  Compare the Home Ventilation Institute (HVI) rating to compare the noise and energy efficiency.  Be sure there are replacement parts available, as well as permanent lubrication.  It may cost a little more for a higher quality fan, but you will not have to replace it as soon.

The capacity of a bathroom exhaust is rated in liters per second (L/s) or cubic feet per minute (cfm).  An average size bathroom will require a fan that draws 25 L/s or 50 cfm.  Anything less than this will not exhaust enough air.

IMPORTANT! Before performing any electrical work, you should always turn off the power at the main panel box.  Place a piece of red tape on the box with a note stating you are working on the electricity or lock the panel box.  Test the wires to be sure the power is off.  Be sure you do not need any special permits.  Have your work inspected by a professional.  Always wear eye goggles and a dust mask. 

Steps on Installing a Bathroom Exhaust Fan as a Replacement

The following steps are for installing a bathroom exhaust fan where the light and fan are operated by the light switch.  However, if you prefer to run the fan and light with separate switches, you will need to run a 3-wire cable between the unit and the existing light switch and install a double switch at the electrical box. 

Exhaust fans with lights/heaters and timers will require additional cable from the existing switch box to the fan.  You will need to follow the manufacturer’s instructions for these more sophisticated models.

Steps on installing a bathroom exhaust fan replacement

1. Shut off the power
2. Remove insulation in the attic where you will be installing a bathroom exhaust fan.
3. If you are replacing a bathroom exhaust fan with a light, remove the existing fixture and disconnect electrical connections.
4. Place the housing in a position which will allow you to fasten directly to a ceiling joint.  If you are not able to fasten directly to a ceiling joint, install wooden braces between joists, which will provide a solid attachment point for the fan housing.  
5. Mark the perimeter you will be cutting by holding the housing in place against the ceiling.
6. Drill pilot holes in the corners and cut with a drywall saw or jigsaw.
7. The housing should be secured in place.
8. Run a length of cable from the existing light switch to the exhaust fan unit.  
9. Use wire nuts to make electrical connections.  Simple fan installation may only need wiring of bare copper to bare copper or white to white and black to black.  More sophisticated models may require more connections.  
10. Attach the ground wire to the grounding clip that is provided on the housing.  Push the wires into the wiring box area of the housing.
11. Install the cover.
12. Connect the duct to the fan housing.
13. Follow instructions from the manufacturer on how far away you should keep insulation. You may need to add dams between the joists to keep insulation at a distance from the unit.
14. Inside the bathroom, install the bathroom unit cover.
15. At the wall switch, wire the cable into the existing electrical circuit.

It is important to properly vent your fan to avoid moisture problems. Vent the fan through the nearest soffit.  Installing a bathroom exhaust fan is an important task that you can do yourself, saving you a lot of money, as well as to reduce health hazards caused by mold.

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Comments (2)

• |2009-09-19 07:55:40 Greg  - how to build a house
  1. get a foundation. a basement or slab will do.
  2. buy lumber and nails, maybe some sheet rock and wires too.
  3. assemble the lumber into a pleasing configuration. use a hammer to put the nails in.
  4. paint the inside and outside of the house. if its raining - wait.
  5. crimp the electrical connections and turn on the lights.
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• |2009-10-06 20:31:47 bathroom ceiling heater
  Very informative. I considered doing those stuffs by my own. I can save money rather than spending a lot on an electrician.
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