How To Vent A Bathroom Fan Through The Wall? (2020 Guide)

Wonder how to install a bathroom vent through a wall?

Routing a bath vent through an exterior wall isn't that tough if you have the right tools — and there are vent kits available that include the flexible vent and exterior cover.

In this guide, I will go over...

  • Tips on the exterior vent installation
  • Low profile bath fans (for vertical installs)
  • Using a hole saw drill bit

Let's get started with this guide!

how to vent bathroom fan through the wall (1)

How To Vent A Bathroom Exhaust Fan Through Exterior Wall?

Installing a bath fan through a wall isn't that difficult of a job, if you have the right tools. It can probably be done in an afternoon if you are organized for the job, but it may take a weekend if you aren't fully prepared.

If you want to vent a bathroom fan through an exterior wall, you will have to cut a 3-inch or 4-inch hole with a hole saw drill bit.

If your exterior siding is vinyl or fiber cement, you will have an easier time cutting the hole. However, if you have a brick exterior it may be a more difficult task, but it can be done with a diamond hole saw which is designed to be much tougher.

After cutting the vent hole, you will have to install an exterior bath vent cover which is usually louvered to keep out outdoor air as well as some type of cage to keep out animals.

If you want to vent a bathroom fan through an interior wall, this would only be feasible if the space behind the interior wall is an unfinished room and only to get to the exterior wall for outdoor venting. It would be necessary to support the bathroom vent hose with ties or clamps to the ceiling joists every few feet to keep it as straight as possible.

Read Also: What Are The Exhaust Fans For Small Bathrooms?

Which Hole Saw Drill Bit To Use?

The main cutting tool will be a 3-4" hole saw drill bit in order to cut the exterior siding or brick.

I recommend using a hole saw drill bit that is a 1/4-inch or 1/2-inch larger than your bathroom vent hose. This will make it signficantly easier to get your vent hose (the rigid section) through the wall.

And if you have a brick exterior, I would purchase a diamond hole saw drill bit in order to have the strength to cut through brick.

Also, if you have a battery powered drill, you may want to opt for a corded drill for the increased power.

Read Also: How To Vent A Bathroom Fan Into An Attic?

Guide Drill Bit

I recommend using a long drill bit to cut completely through the wall in order to act as a guide for the actual hole saw. Just make sure this long drill bit is the same size as the pilot bit in your hole saw.

You want to first cut this guide hole because then you can insert the pilot bit (as part of the hole saw) into the existing hole in order to guide the hole saw for a level cut from both sides of the wall.

I recommend buying the Koopi 4.25" Hole Saw because it comes with the mandrel and pilot drill bit.

Don't Cut All The Way Through At Once

It's also important to avoid completely cutting through the wall with the hole saw.

Just cut about halfway through, and then finish the cut on the other side of the wall. If you try to go completely through the wall with the hole saw, when it comes out on the other end, the wall will likely flake and get damaged — it won't be a clean cut.

This is why it is important to first completely through the wall with a long drill bit.

Read Also: What Are The Best Bathroom Exhaust Fans With Bluetooth Speakers?

how to vent bathroom fan through wall

What Is A Bath Fan Wall Ducting Kit?

I recommend buying wall vent ducting kits that may include:

  • flexible vent hose
  • exterior vent hood with louvers
  • rigid metal pipe adapter
  • clamps
  • bird cage

The small adapter of rigid metal piping is what goes through the exterior wall, and then the flexible vent hose attaches to that rigid piping. The exterior vent hood also connects to the small metal pipe adapter. You don't ever want to install a flex vent through an exterior wall.

And before you complete the hood install, its a good idea to seal around the exterior fan cover with silicone caulking to prevent air and water leakate.

There are ducting kits available that include the flex vent, the hood, and the rigid metal piping. I recommend using the Broan-Nutone Wall Ducting Kit.

Read Also: How To Replace A Bathroom Fan Without Attic Access?

How To Get Power To The Fan?

If you are installing a new bathroom fan (rather than just changing the vent to the exterior wall), it's a good idea to determine where you will get power before you start messing with walls.

There are basically two locations where you can get power, either the electrical panel box or an existing junction box.

You may have to use fish tape to route wiring through the wall, and possibly cut a hole through the top or bottom plate of the wall if you are getting power from an attic or basement. If you have doubts about the wiring, hiring a qualified electrician is recommended.

Read Also: What Are The Best Panasonic Bath Fans With Humidity Sensors?

What Is A Low Profile Bathroom Exhaust Fan?

Sometimes homeowners may want to install bathroom fans vertically on walls, and it will make it a easier installation if it is on a exterior wall.

The bathroom fans that you can install in walls are known as low profile bathroom fans. These low profile exhaust fans have a slimmer profile so that they can't mount in between inside the exterior (or interior) wall cavity.

I recommend the Delta BreezSlim because it is has a very low profile, great for installing in a wall.

Through-The-Wall Ventilation Fans

In addition to low profile bathroom exhaust fans, there are also through-the-wall ventilation fans which you can install in your bathroom.

These aren't specifically made for bathroom fans because some people install them in kitchens, garages, mudrooms, and other locations. But you can install these in bathrooms as well.

And these through-the-wall exhaust fans frequently come with the exterior hood and piping as a kit such as the Broan-Nutone 512M Through-The-Wall Ventilation Fan.

Read Also: What Are Bathroom Fan Sones?

Final Thoughts

I think the main benefit of venting your bathroom fan through an exterior wall is that you don't have to take it up to the roof.

And please don't even consider venting it to the attic or into a wall cavity because it will spew moisture into the space and may lead to mold damage, wood decay, and it attracts insects. You can read my full guide on how to properly vent your bathroom fan through an attic space.

There are bath vent kits that have the exterior cover, flexible vent hose, clamps, and the short pipe section — everything you need for the install.

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Arie Van Tuijl

Arie Van Tuijl

Arie is the founder of Home Inspector Secrets, an online resource dedicated to helping people understand how homes work. He is a licensed home inspector in two U.S states and owns a residential and commercial inspection company (read his full bio on the About page). To ask Arie a question, please use the comment box at the bottom of the relevant article.

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Home Inspector Secrets is an online resource for owners, buyers, and sellers to understand all aspects of home maintenance. We have detailed home guides, product reviews, inspection advice, and much more.