How to Install a Bathroom Fan

Bathroom fans help circulate air and remove moisture in the air. We recommend installing a fan in any bathroom that has a tub or shower.

Installing, upgrading, or replacing bathroom fans are common projects that we work on. However, some people take pride in DIY projects.

Bathroom fans are actually relatively simple, so we wanted to share how you can install one yourself if you’re a “do-it-yourselfer.”

Fan Options

Before you begin you should be aware of the different options you can choose. First, there are two numbers you need to understand.

The first number is “CFM.” CFM stands for “cubic feet per minute.”

CFM measures the amount of air flow you’re going to get from your fan. The size of the room dictates the minimum amount of CFM you need.

The calculation is simple. Measure your bathroom’s length, width, and height. Multiply those together to get the room’s volume, then multiply the volume by 0.13.

So if your bathroom is 10 feet by 10 feet by 10 feet you’d need a CFM of 130. Of course, most bathrooms are significantly smaller than that; the average CFM is generally 50.

Next, you get to decide how loud you want the fan to be. When you buy the new fan look for its “Sones” rating. A 1.5 sone fan would be incredibly quiet, where a 4.6 sone fan would be a more average fan with a louder output.

The quieter fans are more efficient. The louder ones offer a little more privacy.

There are a few other options you can look to as well such as lights or built-in heaters. These are totally up to you.

Installing the Fan

Start by measuring the housing on your fan. The job will be easier if your new fan’s size matches the old size since you’ll just replace the plug-in modular blower assembly after removing the grill. Then you’d put the grill back.

If you’re upgrading the fan to increase your power, reduce your sound, or increase your features you’ll need to take more steps.

In either case you will always begin by using your circuit breaker to turn off the fan’s power. Never work on an electrical project without turning off the power first.

Next, you’ll remove the grill. Removing the motor blower assembly is usually as simple as unplugging it. Then you can disconnect the electrical wiring to the fan.

You’ll have to enter the attic next and locate the fan. Once you’ve found it, look for an exhaust hose or exhaust pipe. Once you’ve located them you’ll need to disconnect them.

You will probably see fan housing attached to the joint or trusses in your attic. Remove that with a power drill.

You might have to install a duct or a duct reducer attachment if you’re increasing CFM or lowering sones. It’s usually better to install a 4″ to 6″ duct if you want the fan to work as efficiently as possible.

If the new fan has larger housing than the old fan you’ll have to measure the new housing and cut your drywall to compensate for the increase in size.

Now, attach the new fan to the joist or truss where the old fan was located. Reconnect the exhaust fan or pipe. Now connect the house wiring to the fan wiring.

Back in the bathroom, you can install the motor blower assembly and connect the plugs inside of the housing. You’ll need to reattach the grill.

Now it’s safe to restore power to the bathroom fan. Switch on the fan to make sure that it is working.

If all of that seems a little confusing the process is also outlined in the Home Depot video which we’ve included below.

If after reading this process or seeing this video you find that you’re not comfortable with the scope of the project it’s probably best to call an electrician. As experienced electricians in Durham, we are happy to come and help on these kinds of projects.

We’ve been serving Raleigh, Chapel Hill and Cary for over 20 years and we’ll be happy to help you as well. Remember, we’re available 24 hours a day – 7 days a week!

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