How to install a vent fan in your bathroom

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Installing a vent fan in your bathroom will help eliminate fogged-up windows, steamy mirrors and stale odors. It will also help prevent all sorts of moisture-related problems, like growth of mold and mildew. In this article we will guide you through the installation process of a vent fan in your bathroom.

First, you will need to determine which size of a vent fan you need for your bathroom. Bathroom vent fans are rated according to how many cubic feet of air they can move in one minute. This is known as the CFM rating. To determine the size of the vent fan, multiply the room’s square footage by 1.1. For example, a 100-square-foot bathroom, will require a 110 CFM-rated vent fan. Vent fans also have a sound rating, measured in sones. They range from 0.5 sones up to 6.0 sones.

For optimum performance, locate the vent fan between the shower and the toilet. Draw a mark on the bathroom ceiling, where you want to place the vent fan. Use an extra long spade bit to bore a hole through the ceiling and into the attic, with 3/8-inch diameter. This is your reference hole. Go up to the attic and clear away any insulation from around the hole. Determine the exact position of the vent fan, using this reference hole. Try to position the vent fan directly between two joists near the reference hole. Take into account any nearby pipes and other obstructions. Note the final position of the vent fan in relation to the reference hole.

bathroom vent fan

To determine what size hole you need to cut in your bathroom ceiling, measure the inside dimensions of the vent fan’s intake port. Use the reference hole as a landmark to transfer your measurements from the attic to the ceiling. With a framing square draw the rectangular outline of the intake port on the bathroom ceiling. Next, cut through the bathroom ceiling on the layout lines with a jigsaw. You will need to wear goggles and a respirator. When you’re almost finished, you will need to support the waste piece with one hand, to keep it from falling and possibly taking some of the drywall or plaster ceiling with it.

Back in the attic, attach a 4-inch, 90-degree duct elbow to the outlet port on the side of the vent fan housing. Aim the elbow straight up and secure it to the port with foil duct tape. Remove the knockout hole on the side of the vent fan’s housing and attach a cable connector. Slide the four metal brackets into the tabs protruding from the sides of the vent fan. Set the vent fan down into place between the joists, centered on the ceiling hole. You might want to use foil duct tape, instead of fabric, because it won’t deteriorate over time.

Next, fully extend the brackets, until they come into contact with the sides of the joists. Secure each bracket end with a single 1 ½-inch drywall screw. Take the flexible duct that comes with the wall cap kit and slip one end over the elbow, attached to the vent fan. Then, secure it with foil duct tape. Feed the electrical cable through the connector and tighten the connector screw to secure the cable.

bathroom vent fans

From inside the attic, choose a spot on the sidewall for the flexible duct to exit the house. It should be located between two wall studs and within 6 feet of the vent fan. You might need to take a few reference measurements, so that you can find the spot from the outside. Mark the hole location on the siding, using the reference measurements, and cut the duct hole through the wall with a 4-inch hole saw.

After securing the wall cap to the outside wall, grab the free end of the flexible exhaust duct and carefully stretch it to the outside wall. Attach the duct end to the wall cap’s connector duct with foil duct tape. From the outside, slide the wall cap into the duct hole and push it tightly against the house siding. Remove the wall cap and apply a bead of silicone adhesive to the siding and gasket around the hole. Then, slide the wall cap into the hole and press it tightly against the siding. Secure it with four 1 ½-inch stainless steel screws.

Back in the bathroom, unscrew and remove the blower motor from the vent fan housing. Make sure to save the screws. Then, unscrew the built-in receptacle from the inside of the housing to expose its wiring. Again, save the screws. Join same-color wires with the ones from the electrical cable you fed into the housing before with wire nuts. Wrap the bare copper wire under the green grounding screw inside the housing and tighten the screw. After that, place the electrical receptacle back into position and secure it. Next, raise the blower motor up to the bathroom ceiling, push its plug into the electrical receptacle inside the housing and secure it with the screws. Lastly, hold the the vent fan’s plastic grille close to the ceiling and slip its mounting wires into the slots inside the vent fan housing. Push up until it’s tight to the bathroom ceiling. If the grille doesn’t hold tight against the ceiling, spread apart its mounting wires to create more tension. You may now turn the power back on and test the vent fan.

bathroom ventilation

The reason why many households still don’t have a vent fan in the bathroom is because the installation process can be quite intimidating. A bathroom without a ventilation fan is like a fireplace without a chimney. The moisture, generated in the bathroom, can migrate into the walls and grow mold and mildew, or blister paint and peel wallpapers.

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