Are Bathroom Fans Necessary(not having one could cost you thousands)

As an Amazon Associate, we earn from qualifying purchases at no additional cost to you.

Bathroom fans have been installed in buildings for decades now. Some people might wonder, are they really necessary and what will happen if it is not installed.

A bathroom fan is necessary even if the building code does not require it. Without it, there is a serious risk for moisture-related damage in the entire house, not just the bathroom. Over time the excess moisture will develop into mold.

According to the building code, an openable window is an acceptable option for ventilation. However, in practice, this is not sufficient. This might be viable in some climates, but not in most places. Cold outside temperatures will make opening a window impractical.

To meet code, the window will need to be at least 3 square feet (0.27 square meters). Half of the window must be openable.

It is highly recommended not to rely only on a window for bathroom ventilation. From my own experience, I can report that this will lead to moisture problems in the attic. If not spotted in time it can be a very expensive problem.

It is very important to exhaust the moist air out of the building envelope. By simply installing a bathroom fan to prevent moisture damage you could save thousands in mold removal and other moisture related problems.

Mold is only one out of 9 reasons why having no ventilation in the bathroom is terrible.

Bathroom Fans Exhaust Moisture Out of the House

Showering creates a lot of moist air. If the moisture is not exhausted out of the house, it can lead to serious problems that can cost thousands to fix later.

The problem is that sometimes the moisture damage will not be in the bathroom where it is visible. Instead, the moisture will make its way to the attic and condensate there. This is what happened in my house. I noticed mildew coming out of the soffit and that’s how I discovered it. Luckily I caught it in time and it had not spread too far so the cleanup was not too bad.

By staying hidden for months or even years the problem can get very serious before it is uncovered. Dealing with mold in the construction of the house can be a very expensive problem to have.

Daily addition of moisture by showering will make it a perfect environment for mold and mildew to thrive.

A moisture sensing bathroom fan(amazon link) will eliminate the risk for moisture damage. Since it will turn itself on when the moisture level rises, it does not rely on people remembering to turn it on. Don’t buy a cheap moisture sensing fan, as the sensors in them are useless. Panasonic units are reliable, and even if the sensor stops working it will be covered by their 5-year warranty.

I highly recommend installing a bathroom exhaust fan in a bathroom where there is a shower or a bath. I have created a quick guide on how to choose the perfect bathroom fan for your needs.

I believe most people who are hesitant in installing a bathroom fan have never had a bathroom without an exhaust fan. I have had the “pleasure” and I can tell you the constant fight with moisture is not worth it

Bathroom Fans Are the Best Way to Prevent Mold and Mildew

By exhausting moist air the bathroom will dry out much much faster compared to just leaving it dry on its own. This will make it impossible for mold to grow on the walls and ceiling of the bathroom. Often the mold starts in cold corners of the bathroom since that’s where the moisture will condensate first, and dry out last.

Of course the bathroom fan must have sufficient CFM to be able to exhaust enough air to make it efficient. Find out how exactly does a bathroom fan work.

An adequately powered bathroom fan will exhaust the moisture before it has time to condensate on most of the surfaces. An additional benefit is that the mirror will stay fog-free.

If you have had mold or mildew problems in the bathroom in the past, it is most likely caused by insufficient ventilation.

The exhaust fan needs to run at least 30 minutes after the shower, in order for the air to dry out. Here you can see it will take almost 1 hour before the moisture level drops to a normal level. This is with the exhaust fan running. It would take many hours without it.

Bathroom Fans Remove Smells

Bathroom fans are very efficient at removing various odors from the room. A properly sized bathroom fan will exchange all of the air in the bathroom 8 times an hour.

This means that shortly after turning on the exhaust fan, fresh air will replace the stale air and the smell will be gone.

While the removal of odors is a matter of convenience when it comes to human-based odors, it’s a different story when using chemicals to clean the bathroom. A bathroom is usually a very confined space and using toxic chemicals in there can spell disaster.

Opening a window during the winter months will be impractical so you are left with a bathroom filled with toxic chemicals.

If you still insist on not installing a bathroom fan, at least get a quality respirator to protect yourself from toxic fumes when cleaning.

highly recommend the 3m 6503QL(amazon link) paired with a 60923 filter (amazon link). This filter offers the best combination of protection from organic compounds and particles. It’s perfect for all types of home improvement projects.

Bathroom Fans Can Be Used To Exhaust Paint Fumes

While the main purpose for bathroom fans is to exhaust moisture and foul odors, they can be used for alternative purposes.

Most people will at some point paint the rooms in their homes. A bathroom fan could be used to ventilate any room of the house while painting. While this is something that will only use once every 5-10 years, it is very handy when it comes time to give a new coat of paint to your living space.

You can read more in my list of Bathroom Exhaust Fans Pros and Cons

Consider A Wall Vent

Broan-Nutone 512M Through-the-Wall Ventilation Fan, White Square Exhaust Fan, 6.0 Sones, 70 CFM, 6"

If running a duct to the bathroom is too difficult a simple solution could be to just install it on the wall. While this is very uncommon in North America, it is perfectly OK to install a bathroom fan on a wall.

Of course, this requires the bathroom to have at least one exterior wall. By installing a fan that is designed specifically for vertical mounting, the installation will be much easier since most of them will include a collar that will go into the wall construction.

Don’t Forget To Install A Backdraft Damper

A backdraft damper is a simple flap that is operated either by gravity or a spring. This will stop the vent from drafting, dripping and as a bonus will keep insects out of your house and ventilation system.

Try to avoid cheap gravity-operated dampers. I can guarantee that it will drive you mad when it starts to flap in the wind.

Instead, invest in a quality spring-operated rubber-sealed damper. I recommend AC infinity dampers(amazon link)  they use quality rubber seals to prevent noise and any air leaks. They have dampers from 4 to 8 inches to fit most applications.

Share a Vent With a Nearby Bathroom

If there happens to be another bathroom nearby, they could share a duct and possibly make the install much easier.

Keep in mind that the duct size must be sufficient in order for both of them to work at the same time.

Does a Toilet Need a Vent

A toilet does not create enough moisture to cause any problems. However, to meet code there has to be an openable window in there. This means that a ducted bathroom fan is not necessary.

While a ducted bathroom fan would be better, a ductless bathroom fan is acceptable in a toilet. They are quite effective at removing odors and do a great deal to help keep the toilet smelling fresh.

Here are 7 more creative ways to help keep bathroom smelling fresh without a ducted exhaust fan.

Using A Ductless Bathroom Fan

A ductless bathroom fan is not suitable for use in a bathroom with a shower or a bath. They are meant for closets, pantry’s and quarter baths(bathroom with only a toilet)

Ductless bathroom fans do not remove any moisture from the air. They filter the air through an activated carbon filter to improve air quality and remove some of the odors.

Learn more about ductless bathroom fans and how they work

What if It Is Impossible to Install a Bathroom Exhaust Fan

While I don’t believe there is nothing that is impossible, it might be very difficult to install a ducted exhaust fan in your bathroom.

A bathroom that is in the middle of the house, with no attic access and no crawl space does make running ducting to the bathroom very difficult.

There are some alternatives that will make the situation better, but don’t fool yourself. They are all band-aid solutions and not long-term fixes.

A powerful dehumidifier(amazon link) for humidity control and a ductless fan(amazon link) to deal with odors will be the best option when a real bathroom fan is out of the question for some reason.


A bathroom fan is a very important piece of any home’s ventilation. The moist air from the bathroom must be exhausted out of the building and the bathroom fan is the best tool for the job. An additional benefit of having an exhaust fan is that it will very efficiently remove odors. This is especially important if you have guests over. Avoid ductless fans as they do not remove moisture from the air. If installing a bathroom fan is out of the question, a dehumidifier and ductless fan combo will make the situation better.

Amazon and the Amazon logo are trademarks of, Inc, or its affiliates.

Recent Posts