Should a bathroom fan hose be vented into an attic? If so, how is it done?
During my home inspections, I have come across many bathroom vents incorrectly installed into attics. A poorly vented bathroom fan can lead to moisture damage, mold, and other issues—but it can be done correctly with a few crucial steps.
In this article, you will learn…
- How to remove the old bath fan
- The steps to secure the new fan to the joists without attic access
- How to connect the electrical wiring from below
- Connecting the old vent hose to the bathroom fan
Part 1: What To Consider Before Replacing Your Bathroom Fan?
Step 1: Check The Housing & Duct Size
Before even purchasing a new bathroom exhaust fan, it may be a good idea to remove the fan cover, and measure the exhaust fan housing in between the drywall.
If your new exhaust fan is larger, you will need to cut some of the drywall with a keyhole saw, and possibly attach wood supports to the joists. If you don’t have much space in the ceiling cavity, you can consider the purchase of a low profile bathroom exhaust fan — these fans have a smaller housing (especially thickness) than regular bath fans.
This is also good time to check the fan duct size. They are almost always either 3″ or 4″. If your new bathroom exhaust fan has a 4″ duct opening, and your bathroom vent is 3″, then you will need a 4″ to 3″ duct adapter to connect them together. Otherwise, you will have to install a new 4″ duct to the outside.
Remember, new bathroom fans rated for 4″ ducts were designed to be installed with that specific vent size. If you install the older 3″ duct, then you can expect the bath fan to run somewhat louder and less efficient.
Step 2: Wall Switches For New Vent Fan
If you want the new exhaust fan to use your old switch, then no more switches will be needed.
But if your new exhaust fan has a light, heater, or humidity sensor, and you want to control it with a separate switch, you will need to purchase and wire the new switch.
Step 3: Decide Upon Extra Features
Before buying your new bathroom exhaust fan, you must decide if you would like any extra features that come with new bath fans.
There are fans that come with humidity sensors that can automatically turn on and off based on a preset humidity or moisture level in the bathroom. This feature is very useful if you have occupants whom you think do not regularly use the bathroom fan, or if you don’t want to have to think about turning it on.
If you would like more lighting in your bathroom, there are exhaust fans with lights included that can increase your lighting, or it may be your only light fixture in the bathroom. There are also exhaust fans that have heaters as part of the fan which will heat up your bathroom within a few minutes, so you don’t have to touch the central thermostat to have a warm bathroom floor.
Part 2: How Do You Remove The Old Bathroom Vent Fan?
Step 1: Turn Off the Power
The first step in replacing a bathroom ceiling fan is to shutoff the power. Nobody wants to get electrocuted for a bathroom fan, heaven forbid. Locate the breaker for the bathroom at your panel box.
The bathroom outlet and light will likely have no power as well, so that is a good indicator that you have turned off the right breaker. To be sure, you can use a non-contact voltage tester to check the wiring inside the exhaust fan.
Simply turn the voltage tester on, and touch the electrical wiring (or anywhere near it) and the tester will start beeping if the power is on.
Step 2: Remove The Grill Or Plastic Cover On Bath Fan
Removing the exhaust fan cover or grill is very easy to do. Just pull down on the plastic cover, and there will be a small gap in between the ceiling. There are usually two metal clips that attach the cover to the housing. Squeezing the metal clips inwards will release the clips from the housing, and then just pull off the cover.
Step 3: Remove the Fan Motor From the Housing
Most often, the motor/fan assembly will need to be separated from the main housing. The main housing is separately attached to the ceiling joists. There may be a screw or two that needs to be removed, but quite often, all you have to do is use a screwdriver to free the motor from the metal housing because it is clipped in.
Some bathroom vent fans will have an electrical plug within the housing that the motor is plugged into. You will have to unplug the fan before you can pull out the motor/fan assembly. If there is no plug, the wiring will have to be manually disconnected, possibly by removing wire nuts.
Step 4: Remove the Main Fan Housing From The Ceiling
Now it’s time to remove the main fan housing from the ceiling joists. Unless you are installing the same model bathroom fan, the old housing will very likely need to be removed.
There will usually be a few screws connecting the fan housing to the ceiling joists. An adjustable metal bracket may also be screwed into the ceiling joists — and the fan housing secured to the bracket. Most new bathroom fans will have an adjustable bracket for you to install customized for the new bathroom vent fan.
Depending on how the metal brackets are connected and your level of access, you may need to use a reciprocating saw to cut the bracket for removal. Be careful that you don’t damage the wood joists.
Step 5: Disconnect The Duct & Wiring From Bath Fan Housing
When the fan housing is free from the ceiling, you may have to temporarily push the metal housing into the ceiling. Once it is pushed upwards, you will now have access to the vent duct that will need to be removed from the housing assembly.
The duct is usually be fastened to the exhaust fan using foil tape or a simple zip tie which will have to be cut. After removing the vent duct, you will need to remove the home’s electrical wiring from the metal housing.
There will likely be a bushing that needs to be unscrewed or wire nuts that need to be undone. A bushing is simply a circular piece of plastic that protects the electrical wiring from getting damaged by a sharp edge where it passes through metal. After you have removed the home’s electrical wiring and the vent duct, you can now remove the old housing from the ceiling cavity.
Part 3: How Do You Install & Replace the New Bathroom Exhaust Fan?
Step 1: Check The New Exhaust Fan Size
After you have removed the old fan, it is a good idea to put in the new fan housing into the drywall ceiling hole to check that it fits. If the new exhaust fan housing is too large, you will have to trace out a new hole onto the ceiling, and cut out the drywall with a jab or keyhole saw.
Besides the ceiling drywall hole, you also want to verify that the housing assembly can be properly secured to the wood joists. If the metal housing doesn’t fit, you may have to secure some additional wood to the joists so that housing can be installed securely. The bathroom exhaust fan should be attached to at least one ceiling joist.
My favorite bathroom fan to install without attic access is the Panasonic WhisperFit because it has a low profile (5-5/8″ housing depth) which makes the installation easier. It is also extremely quiet and you can flip a switch for either 80-cfm or 110-cfm. You can see the latest price of the WhisperFit right here.
Step 2: Pull The Home’s Wiring Through The New Fan Housing
Now is the time to remove the junction box cover on the new exhaust fan (if there is one), so that the home’s wiring can be pulled through and connected to the new motor wiring. If the new bath fan doesn’t have a junction box, then you can ignore this step.
Once you pull the wiring through the junction box or wiring cover, you should secure it using a protective grommet or bushing so the wiring doesn’t get damaged on a metal edge. It is a standard practice to use grommets (or bushings) to protect wiring from rubbing against a bare metal edge. Your new exhaust fan may or may not come with one.
Step 3: Connect the Duct Connector Or Flapper To Fan Housing
The duct connector is a small plastic piece that connects the duct inside the ceiling to the new bathroom fan. The duct connector has louvers or dampers that close when the bathroom ceiling fan is not in use. Always make sure that when you install the duct connector that the flaps are in the correct downward position — allowing air to go out but not in.
There are two ways to install the duct connector. The first way is to attach the duct connector to the duct using foil tape, and then line up the housing assembly into the flapper after the housing is secured to the joists. The second way is to connect the flapper to the housing, and then you push the metal housing into the ceiling — but connect the duct prior to securing the housing assembly.
Prior to screwing the new housing to the joists, you will need to be sure that the old vent in the ceiling is properly connected to the metal housing and to the duct connector. Once the vent is connected, wrapping around the duct connection with foil or metal tape is recommended by the Energy Department.
Step 4: Secure the New Housing To The Wood Joists
If your new bathroom exhaust fan came with hanger bars or a “fast install bracket”, this tool will be very useful in helping you attach the bath fan to the ceiling joists, without having to make wood fillers. Slide the hanger bars onto the metal housing, making sure the tabs are in the right direction as mentioned in this installation manual from Broan.
If there are no hanger bars, then you will simply screw in at least one side of the housing to a single wood joist — bathroom vent fans aren’t very heavy so securing at least a single side should be sufficient.
Step 5: Connect The Home’s Electrical Wiring To The New Fan Motor
Now that the housing assembly is secured, you will want to fully connect the home’s wiring to the exhaust fan wire connections. The wiring was already pulled through the housing but not yet fully connected.
Most new exhaust fans will have quick connects that allows you to insert bare wires into the connectors. Other exhaust fans will require you to twist together the bare wires, and then twisting on a wire nut.
Wire nuts are color coded based on the size of wire that they can be used for as mentioned by Wikipedia. If your new fan doesn’t come with wire nuts, then make sure to buy properly sized wire nuts.
Always remember to connect the wires according to color…
- Hot Wire (black to black)
- Neutral Wire (white to white)
- Ground Wire (green to green OR green to bare copper)
If your new exhaust fan has a heater, light, or humidity sensor, the color codes may be a little different. For example, if your bath fan has a heater, there may be a black to red wire connection instead. Look to the manual for the wiring diagram so you can be sure you are connecting the right wires.
When you are connecting the home’s wiring to the new exhaust fan, it can be helpful to have someone hold up the new housing while you connect the wiring. Once the home’s wiring has been connected to the fan motor, push the wiring into the hole of the exhaust fan or into the wiring compartment so it is out of the way.
Step 6: Seal The Housing With Caulking
In order to avoid air leaks through the exhaust fan and the ceiling, you can apply a thin bead of caulking. Alternatively, you can apply some metal/foil tape to the housing edge.
Step 7: Re-Install the Cover
Now is the time to reinstall the cover or grill. Just like when you removed it, you will have to insert the clips into the holes of the housing — squeezing the clips.
Step 8: Turn On Power and Check Fan Operation
Flip the breaker back on, and check to see if the fan is working. If you have a very quiet bathroom fan, it may be difficult to know that it’s on. You can take a small square of toilet paper and hold it up to the fan to see if there’s suction.
Read Also: Is Your Bathroom Fan Leaking When It Rains?
What’s The Bottom Line On Installing A Bath Fan Without An Attic?
Replacing a bathroom exhaust fan without attic access can be done correctly with minimal problems. Is it easier that having attic access? Definitely not. But if you are aware of the common sticking points, then it isn’t that much more difficult.
The biggest challenges of installing a bathroom fan without attic access will likely be connecting the vent hose to the housing assembly as well as the wiring.
Just remember that you may have to push the metal housing assembly farther into the ceiling so you can connect these things. After it is connected, then you can screw in the housing assembly.