How to Install a Bathroom Fan Without Attic Access

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You can gain several benefits by swapping your old bathroom fan with a newer, more effective one. A well-operating bathroom exhaust fan circulates air and can remove unpleasant odors. Additionally, it brings down the room’s temperature, which is its most important quality. 

It’s important to take the appropriate precautions if you plan to replace your old, rickety bathroom fan with a newer model.

When installing a fan in an attic, you will have to do it differently than if you live in a house without an attic. This is because you can easily reach a ceiling fan from the attic. Therefore, detaching the old enclosure and setting up the newly-installed enclosure can be done more easily.

However, if your house lacks an attic, you’ll have to replace both the housing and the fan below it. Sometimes this is challenging to accomplish, but some houses do not have attics. These instructions will assist you in installing a bathroom fan without an attic space if you’re one of these people. 

Bathroom fan

Steps to Install a Bathroom Fan Without Attic Access

Measure the Fan’s Size 

Your bathroom fan size will need to be determined before you can begin replacing the old one. It’s easiest to choose an exhaust fan with about the diameter of your current one. It won’t be necessary to enlarge the ceiling hole, and some ceiling holes can be very difficult to enlarge.

Nowadays, nearly every fan is rated by a CMF. If you’re unfamiliar with CFM, it refers to cubic feet per minute. Knowing your bathroom’s size will give you an idea of how many CMFs you need. 

Use this formula to select the correct size:

To ensure accurate rounding, round your numbers to the nearest ten. Using the formula above, if you have 8.5 feet of length, 9.5 feet of width, and 8 feet of height, you will have a CMF of 83.89. Consequently, you will need a fan with a CMF rating of 90 or higher.

The average smaller bathroom will require a fan that has approximately 50 CMFs, while a large bathroom typically requires around 100 CMFs. To eliminate the need to enlarge the ceiling hole, choose a fan with the same size hole so that it does not have to be enlarged.

Where Is the Exhaust Going?

Your next step is ensuring the exhaust is making its way outside the house. You may experience several moisture issues if you allow your exhaust to vent into your attic, but you should vent your exhaust outdoors. Typically, the ducts are already in place if replacing the fan.

However, if installing a new fan, you may need to call a professional to build a duck or sidewall for the exhaust to pass through. You can move forward after verifying that the exhaust will safely leave your home.

Inspect Your Electrical Options

Consider your electrical options by inspecting the area. Your new exhaust fan housing would be ideal if you could power it through an existing switch. But, there are many fans available today with lights. 

In most cases, additional switches are required for these lights, and a different switch will have to be installed if this is unavailable.

Take Out the Old Exhaust Fan

You can remove the old exhaust fan since you now have the proper exhaust fan size for your room and know it vents properly. In addition, ensure the fan has the right electrical configuration. Be sure to:

  • Turn off the breaker box.
  • Remove the grill cover.
  • Use a circuit tester to check if the electricity is disconnected.
  • The final step involves sealing any gaps to prevent air leaks.
  • Make sure that the motor is disconnected.  You might need to remove a few screws and disconnect the wiring from the motor.
  • Assemble the fan and remove its housing. You may need to remove your old fan mounting screws, brackets, or other hardware. 
  • Generally, the housing of the fan is attached to the ceiling joists. You will need to remove the mounting screws or brackets below the fan if you cannot reach it from up there. Use the reciprocating saw or oscillating saw when cutting brackets.

Once you remove the old bathroom fan from its original position, you can install the new one. You need to be familiar with the procedure before beginning the project.

Bathroom fan

How to Install a Bathroom Fan Without Attic Access 

Before installing your bathroom exhaust fan, those without access to the attic will need to measure the hole in the ceiling to ensure it will fit.

Hold the fan housing to the ceiling and lightly trace it with a pencil. Once you have traced around it, you can cut it out with a keyhole saw. Remember to measure the circumference of the excess ceiling.

Meanwhile, if the hole is too big, you might need to add extra drywall to cover it up. Ensure your calculations are accurate before cutting the piece of drywall for the ceiling hole. Then, attach the drywall to a large piece of wood and place them inside the hole. 

You must attach it by screwing it into the wood and ceiling. Use spackling to improve the ceiling later on. 

It will make sense to create attic access whenever you need to install a new vent but do not have attic access. Otherwise, connecting the fan to the exterior wall would suffice.

You can connect the fan to the roof or a gable wall to vent upward with attic access.

Mounting Your New Bathroom Exhaust Fan

Besides that, another important aspect you should remember is to mount the exhaust fan to the ceiling joist. There’s a possibility that the hole will extend beyond the ceiling joist. 

If there’s a large space, you can attach a piece of wood to the joist to mount the fan. To make mounting your new fan possible, you must build this out.

Additionally, attaching a piece of 1x lumber directly opposite the ceiling hole is a good idea. Screw the lumber into place with quality screws. The fan housing will be secure on another side if you do this.

Bathroom fanInstall the Duct Connector

After completing all this work, place a duct fitting adjacent to the duct in the roof using HVAC tape or a clamp. When installing the housing, it is important to read the new fan’s instructions and understand the duct’s correct placement.

Incorrectly positioned ducts will cause the housing not to match up properly. The duct fitting should also be securely bolted to the surface of the aperture using a screw. The housing must also line up perfectly with the connector. 

Consult the directions that came with your fan for more information.

Plug in the Electrical Cables

It is now necessary to attach the electrical cables. You may need to remove your fan’s housing to accomplish this. Pull out the knockout plug with a screwdriver when you have popped off the protective cap. 

You must also fasten a cable clamp to the wiring cover, and the wires should be pulled through the clamp from your house. By tightening the screws on the clamp and connecting the wires with wire nuts or quick connectors, attach the wires from the fan to the house wires.

There is no need to worry if you have never used quick connectors or wire nuts, and they’re easy to use. It is advisable to insert a quick connector into the bare wire after the connector is taken out, and that’s all there is to it. It would help if you twisted the wire nuts on the wires by holding the two ends together and then twisting them clockwise.

It’s time to push the wires into your fan’s housing lightly. Screw the wiring cover shut after you have connected the wires, and insert the fan into the hole in the ceiling. 

When installing the exhaust, align the duct connector correctly and screw it into one of the wood supports. Ensure that your screws are driven through the mounting flange securely.

Test Out Your New Bathroom Exhaust Fan

As soon as the exhaust fan is firmly in place, ensure it operates normally. You’ll need to check the wiring if it doesn’t run. 

Last but not least, attach the grill. You can do this by pushing the fan cover towards the springs, squeezing the springs, and being careful not to damage the cover. All that remains is to add a little spackle to your new bathroom exhaust fan.


If you don’t have attic access, you can still replace the bathroom exhaust fan by yourself or get an expert to do the job for you. It takes around two hours to do so by yourself. 

Even before purchasing a new fan, other factors should be considered. So, before buying a new fan, check the fan’s size, determine whether you want to change wall switches, and pay attention to the specifications of the new fan.