3 Best Bathroom Exhaust Fan Venting Alternatives (+ Code Requirements)


bathroom exhaust fan need to be vented. There is no way around it. There are many bathroom exhaust fan options, including how to vent a bathroom with no outside access.

In a nutshell, there are two major categories of bathroom exhaust fan venting options:

  1. Indoor Venting. Example: Does the bathroom exhaust fan need to be taken out? Not necessary. The bathroom vent in the attic is an example of indoor bathroom fan venting (code requirements, as explained next, advise against it, however). We’ll see how you can vent a bathroom with no outside access.
  2. outdoor venting. Taking out the bathroom fan through the wall (sidewall) or ceiling are examples of a standard outdoor bathroom fan venting.
bathroom exhaust vent venting options
Example of installed bathroom exhaust fan (receiving 50 CFM intermittent airflow).

We’re going to cover all the options (both indoor and outdoor venting) you need to vent a bathroom fan with a short step-by-step vent installation process.

However, before that we need to consider bathroom exhaust fan code requirements (Specifically Section R303.3, Section R303.4, Section M1507.2, Section M1507.4 of the Internal Housing Code (IRS),

Now, these codes can be hard to dig up. Still, these very bathroom ventilation requirements are important guidelines we can use (in fact, we need to use them) to properly ventilate a bathroom.

Let’s cover a simplified version of these ventilation codes. Understanding these will later enable us to adequately choose the best exhaust fan venting option for your bathroom:

bathroom exhaust fan code requirements

The code requirements are incorporated into the International Residential Code (IRS). Specifically, residential bathroom exhaust fan code requirements are incorporated into Section R303 Light, ventilation and heating,

The most important parts for bathroom venting are chapters R303.3, R303.4, R303.5.

In a simplified version, these codes state that: “Windows of at least 3 square feet (0.3 m2) in the bathroom, water closet compartment, and other similar rooms shall provide an overall glazing area, half of which shall be open.”

It simply means that you need a large window through which to exit the bathroom. Simple, isn’t it? Well, not so easy if you don’t have a window, or your window isn’t big enough (at least 3 square feet).

Here is where bathroom exhaust fans come in. Bathrooms are also considered in the code no window or small windows and says that if you get ‘a housing unit’s air infiltration rate is 5 air changes per hour or less’, you must use mechanical ventilation. That mechanical ventilation is basically bathroom exhaust fans.

A large majority of bathroom ventilation fan requirements cover the size of fan you need. Something in the context of ‘you need a 20 cfm continuous vent or a 50 cfm intermittent vent’. you can check full code here, The easiest option for sizing a bathroom exhaust fan is to use our CFM calculator here.

The other big part are the venting options. To explain as simply as possible, here’s what the code says:

  • bathroom fan The air has to be exhausted on the exterior of the building (Outside).
  • bathroom fan Attics, crawl spaces, or anywhere inside the building the air cannot be exhausted,

It basically answers the following important question:

“Does the bathroom exhaust fan need to be taken out?”

Yes. Residential bathroom exhaust fan code requirements for any bathroom fan exit. Example: Can you open the bathroom in the attic? No, according to code requirements, you cannot remove a bathroom vent in an attic.

Of course, it is still possible to install a bathroom vent in the attic. You just need to be aware that this is not allowed by current bathroom fan code requirements.

It’s important to keep these code restrictions in mind when you’re installing vents.

Now, with all this in mind, let’s look at how to install a bathroom fan and what bathroom venting options are available to you:

How to Ventilate Bathroom Without Windows?

The name of the game here is how to vent a bathroom exhaust fan. This, of course, implied that you don’t have a bathroom window.

With a large enough bathroom window – at least 3 square feet and achieving a minimum of 5 air changes per hour – you simply ventilate the bathroom through that window.

Here we will list the options on how to vent a bathroom with no outside access. This includes ventilating the bathroom fan through the wall, through the ceiling, to the attic, through the soffit, to the ductwork, and through the gable:

1. How to vent bathroom fan through wall? (+installation)

The most popular way to install a fan in a bathroom is through the wall. This is the easiest and most widely available way to ventilate a windowless bathroom.

For through-the-wall ventilation, you basically just have to pick up the bathroom exhaust fan on the right and install it through the wall. For this you have to make a hole in the wall. On the inner side, you have the bathroom, and on the outside, you have the outside; This is smooth ventilation.

Here’s a short step-by-step DIY way of how to install a bathroom vent through a wall:

  1. Choose a position on the wall where you want to install the bathroom exhaust vent. Where to put exhaust fan in bathroom? You want to reduce the humidity, and the moist air sinks to the floor. You should place the fan near the bottom of the bathroom (perhaps 1 foot above the floor to secure the vent in case the bathroom floods).
  2. Measure the fan and label the wall. Use a measuring tape to measure the dimensions of the fan, and label these dimensions on the wall. Example: If you have a 12×12 inch fan, mark 12×12 on the wall. You’re basically labeling where the hole should be through the wall.
  3. Make a hole through the wall. This is the key part of how to install a bathroom exhaust vent through the wall. In most cases, you can use a power jigsaw to cut out that section of the wall. Use a hammer to break off the remainder. With harder walls (stone), you’ll need more powerful equipment.
  4. Clean the whole rabbit. It is important that you have a clear opening before installing an exhaust fan in a bathroom.
  5. Insert a through-the-wall bathroom exhaust fan. Be sure to attach the fan to the joists (you use the 1 1/2-inch screws on the end of each bracket).
  6. Attach exterior wall caps or shutters. Tighten it with screws.
  7. Fix electrical connectors. This will take care of the wiring, and connection to the electric grid.

This is 101 how to install a through wall bathroom exhaust fan. It requires some technical skill and time but it is the most elegant way to ventilate a bathroom without windows.

2. How to Vent a Bathroom Fan Through the Ceiling?

Another way to get the bathroom exhaust fan out is through the ceiling. You can think of this roof vents as through-the-wall vents for bathroom fans; Just replace the wall with the ceiling.

Here’s an important adjustment to make sure Insulate the exterior well, The primary purpose of a roof is to keep your home dry. Any hole in the ceiling, even from a bathroom exhaust fan, is not acceptable.

That’s why you usually use asphalt roof cement to cover the entire exhaust fan.

For a step-by-step method on how to install a bathroom exhaust fan through the ceiling, you can check out the previous chapter on Wall to Wall Installation.

The process is largely the same – instead of cutting a hole in the wall, you’re cutting a hole in the ceiling. You may need some extra flexible 4-inch or 6-inch ducts. Make sure on Step 6: Attaching the External Shutter Cap. That hat will have to withstand heavy rain and even snow.

3. How to Vent a Bathroom Exhaust Fan in the Attic?

It’s quite unbelievable how many homeowners have only one possible ventilation option left: to vent a bathroom fan in the attic.

Now, much has been written about bathroom fans to attic ventilation options. You may also know someone who has a bathroom exhaust fan attached to the attic, or has seen such an installation.

Needless to say, it is practically possible to install a vent from the bathroom to the attic. The only thing you pretty much need to do is drill a hole between the bathroom and the attic; You can view the through-the-wall installation process.

However, you need Pay Attention to the IRS Guidance Here, It’s not so smart to channel high relative humidity air from the bathroom to the attic. This can increase the risk of moisture building up in the attic. Therefore it is not advisable to install a bathroom fan in the attic.

On top of that, IRS requirement codes specifically recommend (we can even use the word ‘prohibited’) to expel the air from the bathroom via a bathroom fan into the attic.

3. How to vent bathroom fan through soffit?

Taking out a bathroom fan through a soffit is usually easy through a wall or ceiling. This is because the soffit is not as thick as the wall and is easier to cut.

To install a bathroom fan through a soffit, follow the through wall installation procedure described above. You can fit the look of a less difficult wall to work with the soffit.

Bathroom fan through soffit installation is also not recommended against code requirements. This is outside bathroom ventilation, you can get either 20 cfm continuous airflow or 50 cfm intermittent airflow, and it’s basically an easy way to learn how to vent a bathroom effectively.

Hopefully, you’ll find all of this useful in deciding how you want to deck out your bathroom without windows.

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