How to replace a bathroom exhaust fan without attic access

In the bathrooms, which has no windows, the best solution is an exhaust fan. Bathroom fan has many benefits, removing odor, improving air quality and protecting us from bacterias and mold, which can intrude our health and also make wall paint to peel, rot, and get greenish color. If you renovating your bathroom or you need to replace your noisy bathroom exhaust fan, and you haven’t done that before, you can find that process challenging. In this article, you can see the preparation and materials you will need as well as a guide through each step of replacing your bathroom fan. If you want a fan with some features, you can always opt for exhaust fans with light and heater.

Victory loves preparation!

The most important thing is preparation, which includes – selecting materials, selecting a fan for replacing, and measuring existing fan and fan duct. It’s the easiest installation if you need to replace the existing fan because you can use existing switches, ductwork, and wires. Also, because you will get a fan of the same size as your existing fan, that means you don’t need to adjust the ceiling opening. Later in this article, you can see how to select a fan. We make a difference between fans by CFM, which stands for cubic feet per minute. That’s a measure of airflow. As a general rule, small bathrooms typically require around 50 CFMs, while lager bathrooms require around 100 CFMs. There is a formula for determining how much CFMs fan should have for your bathroom: Height x Length x Width x .13 = X numbers of CFMs (round up to nearest ten) Example: 9 feet x 10 feet x 8 feet x .13 = 93.6 CFMs Choose a fan of 90 CFM or larger. You take down your fan cover and take precise measurements of the exhaust fan housing. The exhaust fan housing should be positioned amidst the drywall. That may not be too hard if you are replacing an existing fan, as you won’t need to adjust the ceiling hole.

1. How to determine the exhaust route?

Your exhaust fan must vent outside. Since you don’t have access to the attic, you will need to vent out through the sidewalls of the house. That means that your fan ventilation pipes go through the sidewalls of your home, which should be installed when the house was built. (If you don’t have a duct leading to a sidewall vent, you should call a professional for help.)

2. How to determine electrical options?

Like we said earlier, it’s most comfortable when you are changing an old exhaust fan in the bathroom. Then you can use old switches and wires for the installation of a new fan. If your new choice is a bathroom exhaust fan with light and heater and/or some other new features, you will probably need an additional switch or double switch and new wiring to operate a double/ additional switch.

3. How to remove the old bathroom exhaust fan?

Ones you did the preparation and established fan size, exhaust route, and electrical options, you can start with disassembling and removing old bathroom exhaust fan.

a) Turn off the breaker to the fan

The first step should be turning off the breaker, switching off the power, and assuring that electric power is off, so you avoid dangerous situations. Now test it – remove the grill cover of the fan and use a non-contact circuit tester to check that power is off. If it beeps – there is still electricity in the wires.

b) Remove the motor from the housing

The next step is removing the motor from the housing. It’s usually held in its place with screws so that you will need a screwdriver for that type of screws. Remove screws and disconnect the motor from the wiring and housing. (If there is a case where the fan has an electrical plug to cap the motor into the housing, you will need to unplug the fan first so that you can remove the fan assembly or motor)

c) Remove the fan housing

When you removed the motor from the housing, it’s time to take away a fan housing from the ceiling. Depends on a manufacturer, types of securing the housing may vary. In most cases, the fan is secured in place by mounting screws to the ceiling joists. Therefore, you need to remove screws to remove the fan housing from the ceiling.

d) Remove duct and wire connections from the housing

It’s time to disconnect any connections inside the fan housing. You need to push and move around metal housing so you can get the best access to the vent duct and wiring. Cut the foil taping that holds in the place fan duct and remove it. Now unscrew the bushing hose that securing the electrical wiring and remove it. You are well prepared for the main part of the job.

4. Mounting the Exhaust Fan

a) Adjusting the ceiling hole

You need to check does new fan fits to the ceiling hole. If not, it needs to be adjusted. Hold the housing up to the hole to check. If the hole its too small, trace the housing up to the ceiling and after the cut, the ceiling with the keyhole saw by measurements. If the hole is too big, then you will need to patch the ceiling with the piece of drywall. Cut the piece of drywall, attach it to a piece of the wood, set in the hole, and put screws through the ceiling into the wood. Make sure that house assembly is adequately secured on the wood joists.

b) Duct connecting

You can attach the duct connector (the flapper) firmly to the duct with a clamp, or you can use a soil tape. Be sure you follow exact instructions so the housing will line up correctly. The duct should vent to the outside. Then use a screw to secure the duct connector to the edge of the hole so that it will line up with the exhaust on the fan housing. Determine where it will attach the fan housing and secure it to the ceiling with a screw.

c) Connect the wiring 

Let’s see how to wire the bathroom exhaust fan. If the exhaust fan box has junction cover, remove it, so you get access to the home’s wiring. Also, remove the knockout plug with the screwdriver. Secure the cable clamp to the hole on the wiring cover. Pull the house wires through the clamp and tighten the screws. Connect the fan wires to the house wires matching the colors, using quick connectors. (The white wire is neutral and connects to the white house wire, green is the ground and connects to the green or the bare copper house wire, and the black wire is “hot” and connects to the black house wire. ) Push the wires in the housing and secure the wiring cover to the housing with screws.

d) Almost done!

Insert the fan into the hole on the ceiling and check if the exhaust is lined up with the duct connector. Secure it to the mounted wood supports with the screws through the mounting edge. Turn on the power and check does your new bathroom fan work. Squeeze the springs of the grill into the slots and push the cover toward the fan to install grill in the place. (If you were adjusting ceiling hole to fit your new bathroom fan, you need to fix with spackling and paint to look like new.)


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