How to Install Ductwork for a Bathroom Exhaust Fan

Keeping mold and mildew out of your bathroom can be a never-ending battle. Every time you run hot water, you create steam. That steam penetrates every crevice, and soon cools down and turns to water. Essentially, everything in your bathroom gets wet at some point. When this happens in a protected area that doesn’t dry efficiently, you have created a prime breeding ground for a multitude of mold spores.

While there are many products on the market that will kill the spores and clean the stains that they leave behind, the best treatment is prevention. By installing a bathroom exhaust fan, you can keep them from ever finding a place to get a foothold.


Once you have selected the product that you want to install, it’s time to make sure that you have all of the necessary tools. You will need screwdrivers. You’ll probably need both a Phillips and flat head. You will use these to mount the brackets within the electrical box and for the housing on the fan.

You will also need an exhaust duct kit. If you don’t already have a fan system in place, you will need to install a vent to relocate the air that you are sucking out of your bathroom. You can buy a kit that comes with all of the necessary pieces to do this. In addition to these tools, you may also need a jab saw. This will be used to cut the access hole in your ceiling.

How to Install

Ideally, your new exhaust fan will be mounted right over the hole that is in your ceiling for your light. In the rare instance that you don’t have an overhead light in your bathroom, you will need to create one. Use the duct kit that you purchased to determine how big the hole should be.

The sheetrock ceiling can be cut with the jab saw. The cut doesn’t have to perfect since the outside housing of the fan will cover any mistakes, but you still want to be fairly accurate so that you don’t lose any insulation value around the outside of the duct pipe.

The duct kit is simple to install. You will need to mount the box that your fan will hang on right above the hole. This box can be attached directly to the joist or, if the hole is too far from the joist, you can use the special hanger that comes with the kit.

This hanger consists of a steel bar that lays across the joists and allows the box to slide back and forth, so that you can locate it directly over the hole. Attach the length of duct hose onto the mounting bracket .

Once the hose has been run to the attic, you will need to find your way to the closest roof soffit. Cut a hole into the soffit according to the instructions that came with your kit, and attach the hose to the vent that mounts on the outside of the soffit.

This vent should also be included in your kit. Since the soffit faces down, you don’t have to worry about rain, snow or other debris getting into the exhaust pipe, and the moist air from your bathroom will be safely pumped outside.

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