Want to know all of your bathroom fan venting options?
Bathroom fans ultimately need to vent to the outside to expell all of that bathroom moisture, but there are many different ways to do it.
In this venting guide, I will go over…
- Ceiling to exterior wall venting option
- To the roof venting installation
- Soffit bath fan venting option
- And why bath fans should be vented to the outside
What Are My Bathroom Fan Venting Options?
When I inspect homes for buyers, I have seen so many different bathroom venting installations — it would make your head spin. Some of these bathroom fan venting options are terrible, like burying a vent under the attic insulation, or just leaving the vent inside a wall cavity.
There are just a handful of bathroom fan venting options such as ceiling to wall, roof, through-the-wall, soffit, and lastly to the attic. All of these bathroom venting options have their pros and cons, but venting into the attic is definitely not recommended by home inspectors. The most common exhaust fan vent option is the ceiling to exterior wall option, and the second most common is the ceiling to roof venting install.
Let’s take a look at all of these options and get into the details…
#1. Ceiling To Wall
The most common bathroom venting option is when the fan is installed in the ceiling, and the vent goes to an exterior wall. It may go straight across the bathroom ceiling and immediately to an exterior wall. However, the bathroom vent may also have one or two additional bends or turns—but ultimately it still goes to an exterior wall.
The bathroom vent has a vent hood with a flapper which keeps out rain and pests from getting inside through the vent hose.
Bathroom Fan Exterior Cover (Imperial)
Perhaps the biggest downside of the ceiling to wall venting option is that it is vulnerable to animal intrusion. The most common animal that causes vent clogs is the bird because it nests inside the vent. The nest can completely obstruct air flow which will make the bathroom exhaust fan more or less ineffective.
Another downside with the ceiling to wall venting option is that it is vulnerable to exterior rain intrusion — but much less than a roof vent installation.
To minimize water problems, you want to make sure that the hood is thoroughly sealed with exterior caulking and that the vent cover is intact.
Read Also: How To Vent A Bathroom Fan Through A Wall?
#2. Roof Vent Installation
The second most common place to vent your bathroom fan is directly to the roof.
A special metal roof vent is installed that keeps out rain and animals. Preferably made out of stainless steel, the roof vent needs to be hardy to withstand the exterior elements — much more than cheaper plastic wall vent covers.
One commonly overlooked consideration is insulating the duct hose as it goes through the attic area. Since you will be expelling bathroom temperature air through the attic, it may cause moisture problems in the attic.
If the attic air is very hot, and the bathroom air getting exhausted is cold, then these temperature differences may cause water to bead on the outside or inside of the vent and ultimately causing moisture damage in the attic.
It can also work in the opposite situation, when the attic air is cold, and the exhausted air is warm. In addition to possible wood damage, it also may lead to mold growth in the attic. The top enemy facing an attic is moisture.
Steel Roof Vent Cap (Builders Best)
Also, whenever you are cutting a hole into the roof, you are liable that this hole may start leaking in the future. However, I wouldn’t let this stop you because there are millions of homes that have bathroom fan vents going to the roof — it is extremely common.
I definitely recommend having a licensed roofer install the bathroom fan roof vent.
#3. Wall Installation (Through-The-Wall)
The wall installation venting option is when the bathroom fan is installed vertically (rather than horizontally) inside a bathroom wall.
There are two varieties of bath fans installed in walls: through-the-wall fans & low profile fans.
Through-The-Wall Exhaust Fan Kit (Broan-Nutone 512M)
Through-The-Wall Fan Kits
Through-the-wall exhaust fans usually come as kits and come with the exterior cover, a short duct section, and other parts needed for installation. These through-the-wall exhaust fans aren’t just used for bathrooms, but are also frequently installed in kitchens, garages, mud rooms, and other locations.
Through-the-wall exhaust fans are meant to be installed in exterior walls where the venting goes immediately through the wall and to the outside — so the vent section is only a foot or two — and there aren’t any bends or turns.
Also, with these fans, the exhaust duct is mounted directly behind the exhaust fan unlike bathroom fans. With bathroom fans, the exhaust usually comes out of the side — rather than directly behind the unit. This makes it an easier installation in a wall where the venting goes immediately through the wall and to the outside.
Read Also: What Are Bathroom Fan Sones?
#4. Wall Installation (Low Profile Fans)
In addition to through-the-wall exhaust fans, you can also install so-called low profile bathroom fans on a vertical wall. These low profile fans are not as thick as normal bathroom fans, and can comfortably fit in-between wall studs for a vertical installation.
With low profile bath fans, you can also install the vent immediately to the outside if it is an exterior wall. Of course, the venting will have to be slightly offset because it comes out of the side of the fan, unlike directly behind it as in through-the-wall fans.
Low Profile Bathroom Fan (Panasonic WhisperValue)
In addition, low profile fans can be routed upwards through the wall, over the ceiling, and to the outside. You can also route the vent upwards (or downwards) through the wall, and even up all the way to the roof.
#5. Soffit Vent Installation
Probably one of the least common bathroom exhaust fan venting installation is to the soffit.
You should also check with your local building code on this one because not all municipalities allow this venting option.
The soffit is the underside of your roof overhang, and there is usually a type of passive venting installed there called soffit venting. When you install the bathroom fan in your soffit, it may interfere with some of the venting of your existing soffit vent (if you have one). It definitely isn’t ideal to exhaust your bathroom fan to the soffit, but if you have to do it for whatever reason, it is a viable option, and will probably work fine.
Spring Loaded Soffit Vent Cover (Dundas Jafine)
Spring Loaded Soffit Vent Cover
There are custom bathroom vent covers designed to be installed on the soffit, and these vent covers are spring loaded so that when the air flow stops, the spring pulls back the cover to prevent air and animal intrusion.
Read Also: How To Vent A Bathroom Fan Through A Soffit?
Attic Vent Termination (Worst)
Although this is my least liked option, I guess I have to make my audience aware of it.
Almost all building codes state that contractors are not allowed to exhaust into attic space, and that doesn’t just include bathroom fans but also dryer vents. However, I still come across it quite often.
Sometimes contractors or homeowners get lazy and just vent the bathroom fan into the attic, which means the air doesn’t directly go to the outside. Quite often the vent is just laid loosely on the attic insulation, or even worse — buried under the insulation.
But more common the vent actually goes near the outside but it stops a few inches below the ridge vent, or a few inches behind the gable vent. This is definitely better than just having the vent loosely laid on or under the attic insulation (or on the attic floor).
A Few Serious Downsides
However, just to reiterate, building codes do not allow this venting installation, so a home inspector will likely call it out in his report if you ever sell the house. In addition, all of that moisture getting blown into the attic may lead to moisture damage, and it can also lead to costly mold growth.
The easiest way to prevent attic mold growth is to control moisture which means venting all bathrooms to the outside.
If your attic becomes contaminated with mold, the costs to clean up can become astronomical.
Read Also: How To Vent A Bathroom Fan Through An Attic?
So there you have it, all of the options you have for venting your bathroom exhaust fan.
The most important lesson is to always vent your bathroom fan to the outside in order to avoid wood damage and mold growth. The most common option by far is the ceiling to wall venting option. The second most common is the roof vent installation. The third most common is probably the vertical wall installation.