How to Install a Bathroom Fan Roof Vent?

A bathroom fan is surely an inevitable part of your home ventilation system.  But if a fan is not vented, then the whole point of the ventilation system is wasted.

So, how do you vent the bathroom fan? Must you vent it outside or just outside the bathroom is fine?

Like these, many questions pop into your head when you plan to vent your bathroom fan.  In this guide, we are going to show you how to install a bathroom fan roof vent.

Although most people prefer to hire a professional, doing it on your own is undoubtedly going to save you some bucks. And it is not that difficult either. Have a look at the process below.

How to Install a Bathroom Fan Roof Vent?


The difficult part of the whole bathroom ventilation installation is to install the bathroom fan.  The process requires a great deal of work, from choosing the right bathroom fan and exhaust route to the electrical wiring.

If you got that part right, roof vent installation is pretty simple. Just follow the steps below.

Position on the Roof

The first thing you need to do is get in the attic and drill through the roof right above where your bathroom fan is installed. You can also drive a nail from inside for positioning. Make sure you make the mark at the center of the space between the two rafters.

Draw a Hole on the Roof

Next, you have to get up on the roof from outside and locate the nail. Center the vent hood on the nail and measure its edge. Using a knife, make marks on both sides of the nail according to the measurement of the vent hood edge.

Now, you need to cut the shingles from around as per the measurement. Once the shingles are removed, draw a 4-inch hole on the roof with a drill bit.

Connect the Duct

Now you have to connect the insulated duct to both ends, the roof, and the bathroom vent fan. First, you need to remove the vent fan connector fitting and attach one end of the duct with it. Next, use duct tape and nylon zip to secure the connection.

For the other end, you can slide a metal sleeve inside the duct and pass it out through the roof hole after securing the sleeve and duct connection with duct tape.

Alternatively, you can attach a metal duct connector with the roof vent, insert it through the hole, and connect the duct with it from inside using a clamp or tape.  

Finish up on the Roof

If you pass the duct from the inside, make two bend taps on opposite sides of the metal sleeve and nail them to the roof. Apply sealant or roof cement around the roof hole and along the edges of the vent hood.

Place the hood above the hole in the centerline with the duct. Also, apply sealant on the vent hood edges where they overlap with the shingles.

Do You Need to Vent the Bathroom Fan Outside?


Yes, indeed, yes. You have to vent the bathroom fan outside. A bath fan carries a lot of moist and hot air from inside the bathroom, and venting it right into the attic will surely cause some trouble.

The attic is usually cold and needs to remain dry always. Moisture building inside the attic can cause mold formation in the roof timber, leading to its rotting. That is what exactly happens when you vent the fan into this space.

Older homes might still have fans vented into an attic; however, nowadays, in most places, the building codes suggest outside venting of the exhaust fan.

Another mistake people tend to make is venting the exhaust fan to the soffit vents. These are designed to regulate airflow into the attic. So, what happens when you connect the vent, the exhaust to the soffit vents?

Well, the moist bathroom air gets pulled into the attic and, in the winter, condenses inside. Gradually moisture builds up on the roof timbers and triggers mold. It can lead to frost, too, that eventually melts and wets the insulation.

So, basically, venting bathroom exhaust into the soffit vent is the same as venting it directly into the attic.

Some Questions You Might Ask


Venting your bathroom fan is not a very difficult task, but some simple mistakes in the process can induce long-term damages to your home. So, below are some queries that might be helpful if you know in advance.

Can I Vent a Bathroom Fan Through the Roof?

Yes, you can vent a bathroom fan through the roof. Good ventilation aims to make sure the moist air is directed straight to the outside. And you can achieve that by venting the fan to the roof or sidewalls.

But make sure there is a vent hood cover. The cover prevents the cold outside air from getting into the duct. It also includes a strainer that helps to prevent any insects from getting inside. Sometimes birds tend to nest inside the duct, and a strainer helps to eliminate that too.

Where is the Best Place to Vent a Bathroom Fan?

As you can’t vent inside the attic, you are left with two options. Either you vent through the roof or the sidewalls. Now, there are few problems with venting through the roof.

Roof openings are prone to leakages, and if you already have a chimney or some other sort of ducts through the roof, it is better to avoid this option. Multiple openings at the roof can be problematic.

Another option is to vent through sidewalls. The installation process is almost the same as through the roof. You need to make a hole of about 3 to 4 inches in the wall and pass the ducts through it. And finally, seal the wall opening with a wall cap or vent hood.

Wall vents don’t possess a leakage problem and are preferred over roof vents.

Can You Install Bathroom Fan without Attic Access?

Running your bathroom fan ducts through the attic is the most convenient way of vent installation. Attic access makes it easier for you to position the duct and make openings.

However, not every house has an attic or access to the attic. Nevertheless, installing a bathroom fan is doable without attic access.

And you can achieve that by running vertical ducts through the nearest ceiling and exterior wall joints. You can’t make openings at the junctions, though.

Wrap up


Installing your bathroom fan vents is not something you need a professional for. With some basic tools and knowledge of do’s and don’ts, you can do the job by yourself.

Our comprehensive guide on installing a bathroom fan roof vent covers everything about the installation process. Remember not to vent directly into the attic or to the soffit vents, as it can do more harm than good.

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