Proper bathroom ventilation is often overlooked in homes, leading to a variety of issues from mold to rot when left unchecked.
There are several bathroom exhaust fan venting options that can address humid air in these bathrooms, however.
Whether you have a fan already installed and want to reroute the venting or plan to install a new fan in a bathroom, there is a venting system that is suitable for your home.
We will start by covering the four most popular options for homeowners today with through-wall, roof, and soffit-based venting.
We’re also going to talk about why this type of venting is essential and the one area of your home that you should never vent fan exhaust through.
Bathroom Ventilation Explained
A bathroom exhaust vent is something many people take for granted until they are overwhelmed by steamed-up mirrors or mildew in a shower.
Bathroom exhaust fan venting also goes under the radar when people are looking for a new home. Unless you shower or bathe with the door open, warm air from a bathroom needs somewhere to escape.
Bathroom exhaust fans draw that warm air and moisture in before using a bathroom vent to send it out of your home. Bathroom fans also remove foul odors from the area along with stale air ensuring your bathroom feels fresh. Unfortunately, the layout of some homes makes ventilation challenging.
The ceiling-to-wall venting option is standard but not always an option. What works in one area of the world may not in another as well.
You have to keep building codes in mind and the layout of your home to find the best pathway to vent exhaust from bathroom fans.
1. Ceiling-To-Exterior Wall Venting Option
- Less ducting
The easiest way to vent a fan for most homeowners is through ceiling-to-wall bathroom vent options.
In these cases, the fan in the ceiling has venting that runs directly to an exterior wall. This venting terminates at the wall, where it’s covered by a vent hood and flapper.
These flappers open as exhaust is expelled and close when the fan is off like dryer vents. This helps prevent pests from getting into the bathroom.
There are also models with automatic shutters and other high-tech features if you can handle wiring or plan on a professional installation.
There are budget-friendly models like the HWG wall vent from Calimaero, which has a stainless steel cowl, thick rubber seal, and foam stopper to prevent noise.
If you prefer something more discreet and stylish, you can’t go wrong with this HG Power, which is spherical and made from 304 stainless steel.
Plastic housings and vents are cheaper but will not last as long when exposed to the elements. Going with a ceiling to exterior wall ventilation is usually the easiest and cheapest method for homeowners to tackle themselves, but not exactly foolproof.
While it’s a code-friendly approach, ceiling-to-wall venting isn’t the most aesthetically pleasing option and is a place where birds attempt to build nests. Flappers should help keep them out, but blockages are something you have to keep an eye on.
2. Roof Vent Installation
- Wide range of options
- Pest-proof designs
- Larger vent
- Possibility of leaks
While a ceiling-to-wall installation is the most common option, plenty of homes run bathroom exhaust venting directly through the roof. Roof vents are easy to identify by the vent hoods that rest on top of roofs and are best suited for second-story bathrooms and bathrooms that give you a straight shot to the roof.
A roof vent is more durable than wall vents considering they are more exposed to the elements. You can choose kits like Broan RVK1A, which has almost everything you need like a vent hose to go from the bathroom exhaust fan to the roof.
Most roof vents have similar styles, so that you won’t see much difference between the Broan and this roof vent cap from Builder’s Best.
Condensation can be a problem with this type of roof vent in attics, however. A significant temperature difference between the attic air and the exhaust air can cause condensation on the ducting.
That can drip into an attic space leading to model or mildew over time. These bathroom fan venting options will need to be flashed in and sealed to prevent leaks, so it’s best to have a roof exhaust vent installed by a professional for the bathroom.
3. Through Wall Venting Option
- treamlined design
- Multiple venting options
- Reasonably priced
A through-wall bathroom fan is a way to get around situations where you can vent upward or don’t have a bathroom fan installed. These low-profile models are designed for wall installations on any vertical interior bathroom wall.
You can vent a low-profile fan like the Panasonic WhisperWall, by going up and over the wall to the exterior of your home or directly through it.
This is an excellent alternative for homeowners that don’t have a bathroom exhaust fan installed or can’t go upwards with their ventilation.
The advantage to using a wall-mounted bathroom fan is its straightforward nature and versatility.
They are easier to install than ceiling-mounted models, although you will have to hire an electrician if you aren’t comfortable with wiring.
As with any ventilation that requires outside access, you’ll also need to be careful about leaks around the outlet or hood.
4. Through the Soffit Vent Installation
- Discreet venting options
- Potential code violation
- Interference with attic ventilation
- Challenging installation
The soffit vent fan method isn’t the most common or the most popular. That means a soffit vent should be one of the last options when going through the roof, wall, or using a low-profile exhaust fan won’t work.
The soffit covers the underside of a roof overhang and prevents damage to the rafters. It also provides a form of ventilation in these areas, which is why some soffit is slotted with small vents.
The advantage of running a duct to one of these plastic vents is minimal compared to the potential drawbacks.
You’ll also want to check with the building codes in your region if you can vent bathroom exhaust through the soffit vent on your home. If you’re still interested in this method, the video below will give you a good idea of what to expect going forward.
5. Exhaust Fan Ventilation Through Attics
- Against building codes
- Mold growth
- Attic damage
When you’re looking for the best ways to vent a bathroom fan, an attic is one of the first things to come to mind.
These areas are often empty and could already have a roof vent to help with airflow and heat in an attic. Well, we’ve got bad news.
You should never run the exhaust from a bathroom fan into an attic.
Running bathroom fan exhaust into an attic can result in massive repair bills from mold or rot as the hot air doesn’t go outside – it simply goes into the attic.
It’s not allowed in building codes for a good reason, so don’t consider terminating a vent in the attic.
Alternative Ventilation Options
All of the methods we’ve mentioned assume you already have a bathroom exhaust installed, aside from the low-profile option.
What about if you don’t have a bathroom fan installed and can’t get access to an outside wall or roof?
That’s an issue that faces millions of homeowners each year, leaving them with stuffy bathrooms and mildewed caulk in showers. If you can’t get access to the outside, you could use floor ventilation.
These vents are perfect when ducting runs through basements, which may also offer outside access. There are models designed for this purpose, but simple systems like this one can also suffice at floor level.
It’s also possible to use a dehumidifier in a bathroom to decrease humidity levels and prevent mold or mildew from finding a foothold.
Opening up the area after steamy showers will help, along with hanging damp towels in another location instead of the bathroom.
The Bottom Line
The building codes in your area may not require a bathroom fan, but using one can remove odors and moist air from these areas in seconds.
That’s only if the ventilation is handled properly, as poorly run ductwork or unsealed vents will lead to a variety of new problems.
With that in mind, while we do feel like several of these methods are something a handy homeowner can tackle, don’t underestimate issues that could lie behind the walls in older homes.
f you’re in doubt and want a worry-free experience, bring in a professional to assess the situation.
Can You Vent Two Bathroom Exhaust Fans Through One Wall or Roof Vent?
No. It could violate building codes, and you’ll more than likely end up blowing air from one bathroom to the next instead of outdoors. The easiest way to vent two bathrooms through one vent is with an inline centrifugal bathroom fan installed in the ductwork, not the bathroom ceiling or wall.
How Long Should a Bathroom Exhaust Fan Run?
Around 20 minutes after a shower should be enough time to clear out excess moisture from the area. You can run them longer, but it’s not good to leave them running overnight. This could burn out the motor, and it will increase your electric bill.
Can You Vent a Bathroom Fan Into a Crawl Space or Garage?
While it may seem tempting depending on the layout of your home, it’s not advised. Expelling warm air into either of these areas could lead to mold or structural damage.
Will a Wall Exhaust Fan Bring Fresh Air Into a Bathroom?
No, a bath fan is designed to pull warm air out through an exhaust duct. Vent covers, soffit venting, and other bathroom venting options on our list aren’t geared for cleaning bathroom air or replacing it.
Should You Use Flex Duct or Vent Pipe for Bathroom Venting?
Rigid ducts are more durable, but only suitable for straight runs whereas flexible ducting is more forgiving best when you need to go up or around things.
Can You Use a Window for Bath Fans?
Yes, just like you can with an air conditioner or window fan in your home. While it won’t be quite as effective as a traditional unit, a low-profile bathroom fan can help prevent steam buildup and moisture in bathrooms.
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