How to Install a Bathroom Fan Where One Does not Exist?


Persisting moisture in the washroom can cause stale odours.  Moreover, damp air is a potential enemy of fabrics like curtains and towels, bathroom paint, wallboards, fixtures, windows, doors and cabinets. A rise in humidity levels can also lead to the breeding of microorganisms, mildew and mould, negatively impacting your health. Considering all the harm excess moisture can do, it becomes crucial for all households to control it.

Installing a bathroom ventilation fan is the best solution to this problem. It can improve your indoor air quality by removing very humid air through a vent ducted to the exterior of your house. You can either contact a professional for the installation or get it done yourself. However, if you plan on the latter, you need to know how to install a bathroom exhaust fan successfully. 

Things To Know Before Beginning The Installation

Prepping comes before installation, and here are a few things to consider:

What is the CFM rating?

Before installing a bathroom fan, you need to know what size is fit for your bath. Determining the CFM rate (Cubic feet per minute) is the first step in prep to purchase a fan with appropriate strength for your bathroom.

  • CFM is how much damp air the vent removes per minute. You understand that as compared to smaller bathrooms, you need to buy an exhaust fan with a higher CFM for a larger bathroom.
  • You have to multiply the square foot of the room by 1.1. For instance, if your bathroom is 100 sq ft, you would fit a 110 CFM-rated fan.
  • When you visit the market to buy a new fan, be sure to check its CFM rating, which you will find printed on the box. 

Check the sound rating.

Next, check the sound rating (measured in sones) of the fan before purchase. Similar to CFM, the sound rating of the fans is also printed on the box. Usually, vent fans have a sound rating that varies between very quiet (0.5) to very loud (6.0) sones.

Gather your tools

Having the basic electrical and carpentry skills is enough for a DIY vent fan installation. Before commencing, it's best to keep all required materials & tools at your hand's reach. Here's a list:


Power Drill



Combination Pliers

Flexible duct pipe (around 6 ft)

Screws and silicone Caulk

Vent Cap

Wire Nuts

Roofing nails, cement & shingles, safety harness, roof brackets (for roof work)

Mask to block dust from drilling

Cordless drill


Safety glasses

Since this will be a new installation, there won't be ducting in the room. You will be able to route the tubing outside your house when you can access the attic space above the bathroom ceiling.


Step 1- Find the power source.

Check the local electrical code. Depending on that, you can either run a complete circuit for your fan or share it with the bathroom lighting circuit. If you are comfortable with electrical work, establish a new circuit to the ceiling area by running a cable from the service panel. Or else get professional help to finish the task.

Step 2- Identify the Vent point.

Follow these pointers to locate the vent spot:

Inside the bathroom

A direct duct route from the fan to the exterior of the house

The distance between the vent and the exit point should be 6 ft or less.

Avoid sharp bends; they can hinder the airflow

Locate near the area producing maximum moisture, i.e., near the tub or shower

Ideally, run the ducting to a side wall to avoid the chances of roof leaks in future and shingle work. Once you've located the point, drill a hole right at the centre.

Step 3- Cut the exterior opening.

Take your vent cap, pencil, silicone caulk, cordless drill & reciprocating saw and access the sidewall.

Place the vent cap across the locator hole and put a round mark with a pencil where the round vent will fit.

Take the locator hole as the start point and cut the hole using the saw. Apply the silicone caulk and use the screws to attach the roof cap.

Step 4- Cut the Interior Opening

Locate the bathroom joists

Use the paper template or metal fan housing parallel (whichever is available) to mark the cut lines.

Take a jab saw and cut through the drywall

Step 5- Fit the vent fan to the joist.

Get yourself a partner for this step. Take the bathroom fan housing, screws, light and the drill and access the attic.

Position the fan into the interior cut-out hole

Use the cordless drill to screw it into the joist's side. If not, suspend the fan in a way so that it isn't adjacent to the joist. Many vent fans come with suspension brackets.

Pass the wire through the fan housing side and ensure that the wire extends at least 7 inches into the housing.

Step 6- Run the tubing from the fan to the outside.

Go to the bathroom and ensure the fan's vertical placement. Take the flexible ducting tube to the attic and attach it to the fan & vent. Avoid bends as much as possible.

Step 7- Attach the fan unit to the housing.

Follow the manufacturer's instructions to complete this step in the bathroom. You need to hardwire the stripped end of the electrical wires into the fan unit. If you don't feel confident about wiring it yourself, contact an electrician.

Reattach the cover when done.

Now that you're almost done with the installation attach the decorative plastic grill and turn on the circuit breaker. That's it; go back to the bathroom and turn the switch on to test your new bathroom fan.

About the Author Mike Chua

Vircet is your one-stop modern products website that offers you detailed reviews based on efficiency, capacity, design, and performance. We help you make better decisions.

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