How to Install a Bathroom Vent Fan

Javi Calderon

How to Install a Bathroom Vent Fan 

Most people are under the impression that the exhaust fan found in most bathrooms is in place to provide extra privacy for bathroom users. While this is a popular use, the ventilation fan is actually installed in order to remove excess moisture in the bathroom that can cause paint pealing, mold and mildew. Installing an exhaust fan, in most cases, is a relatively simple, do-it-yourself project. 

While specifics will vary by product, and be explained in the manufacturer’s instructions, we are going to discuss the installation process in general.

First off, the materials and tools that you will need: 

Phillips head screwdriver

Flathead screwdriver

Wire cutters


Jigsaw or drywall saw

3-wire or 2-wire cable

Dryer vent duct

Dryer vent clamps

Soffit vent

Exhaust fan set

1) The first step is the most demanding, you will have to climb into the attic in order to install your vent fan. Locate where the bathroom is, then remove all insulation that impedes a clear work area. Be careful, insulation has fiberglass that is harmful to breathe and can cause small cuts and irritation if contacted with bare skin. Some fans are installed in the same opening as the overhead light in the bathroom. In this case, you will not need to create a new opening in your ceiling.

2) If possible, use an area that has two ceiling joists that can be used to secure the fan housing. If there isn’t adequate support, add a wooden brace between two joists to provide a solid foundation for the fan. Place the fan housing down against the ceiling and trace around it, then drill pilot holes in the corners, so you can attach the fan grille on the other side. 

3) Use a saw to cut out the traced portion of ceiling and secure the fan housing in place. If you are attaching the fan and light to the same electrical switch, run 2-wire cable down to the light switch. If you want to have separate switches for the fan and the light, use 3-cable wire. 

4) From inside the bathroom, attach the grille to the fan. 

5) Follow the instructions that come with your exhaust fan for connecting the wiring to the electrical circuit at the switch in the wall.

6) Now its time to create the ventilation system for your fan. Connect the dryer vent duct to the fan housing using duct clamps. You will need to attach the other end of the duct to the nearest soffit vent. The instructions that come with your kit will give you much more detailed instructions on how to accomplish this task correctly. 

7) It is usually best to have the duct running horizontally across the ceiling. This will help minimize the amount of moisture that drips from the duct and onto the ceiling in the attic.

8) Once the duct is in place and secure, fill in around it, and around the vent housing with insulation. Be careful to read your instructions carefully, as different products have different requirements for how close the vent mechanism can me to insulation. Some, especially those that include a light, generate sufficient heat that could light the insulation on fire. So be sure to read your directions carefully.

Step number 6 is crucial. Without proper ventilation, the fan will do little more than make noise. Connecting the fan to a soffit vent will prevent the need for making a roof vent. If your attic is hot and stuffy, it is probably lacking ventilation. Bring in a contractor to advise you as to the appropriate places to add vents. If this is the case, you might as well have him double check your work to make sure your ventilation fan is properly installed. 

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