Addressing water/humidity problems should be a top homeowner priority. That's because moisture supports the growth of mold and mildew. This can make family members sick and cause extensive damage to your house if ignored (read: Protecting Indoor Air Quality at Home). So the purpose of a bathroom fan is to remove the moisture from the air after you take a shower or bath … so don't forget to turn it on!
When Do Homeowners Need a New Fan?
- When your bathrooms don't have an exhaust fan. For many years, it was assumed that if a bathroom had a window, it didn't need a fan. You could open the window to remove the moisture. We've learned most people won't do this because it's too cold outdoors or the air conditioning is running.
- Your bathroom fan is too noisy, a common problem with inexpensive fans. Either the fan(s) were installed by builders focused on minimizing costs or a previous homeowner didn't consider this when buying a replacement fan.
- When running properly, your bathroom fan should hold a sheet of toilet paper tightly.Your bathroom fan has stopped working. This isn't unusual as the expected lifetime of exhaust fans is 10 years. And when you compare the time and materials to try and repair these fans, the low cost of a replacement makes this a more practical solution.
- With bathroom remodels, you might want to upgrade to a more contemporary fan and one that includes lighting.
How Big a Bathroom Fan Do You Need?
The size of the fan matters and we're not talking about the physical size. The bigger your bathroom, the more “cubic feet per minute (CFM)” the fan needs to circulate. The recommendation is a fan large enough for eight air exchanges per hour. For the average bathroom that's 8 ft x 10 ft with 8 foot ceilings, that means you'll need an 80 CFM fan like Panasonic's WhisperCeiling 80 CFM shown here.
When installing a vent fan, make sure there’s at least a 1/2″ gap under the bathroom door to allow fresh air to enter the room when the fan is running. Run the fan for 15 to 20 minutes after showering or bathing to expel all the excess moisture.
If you're uncomfortable calculating the size of your bathroom, here are the minimum bathroom exhaust fan ventilation requirements from the Home Ventilating Institute. Other things to consider are ceiling heights over 8 ft and toilets in separate room … may require addition CFMs.
| Bathroom Size | Minimum Ventilation (CFM) Required |
| 50 sq ft | 50 CFM |
| 50 to 100 sq ft | 1 CFM per sq ft |
| Add up CFM requirements for fixtures: | |
| Toilet | 50 CFM |
| Shower | 50 CFM |
| Bathtub | 50 CFM |
| Jetted bathtub | 100 CFM |
How to Find a Quiet Fan
Have you owned a house where you didn't turn on the bathroom fan because it was too noisy? Even I've done that until it became annoying enough to replace the fans, even though they were brand new. Bathroom fan sound levels are measured using sones, where the lower the number, the quieter the fan. To put these fans in perspective:
| Home Feature | Noise Level (Sones) |
| Standard television | 4.0 sones |
| Typical office noise | 3.0 sones |
| Newer refrigerators | 1.0 sones |
| Bathroom fans | Quiet fans rated 1.0/less sones |
| Rustling leaves | 0.5 sones |
Other Features Available with Bathroom Fans
Most of these fans aren't very noticeable when installed, appearing as another vent in the ceiling. There are other options you can get with your fan. These include decorative lighting, heating elements, timers and even a humidistat to automatically turn the exhaust fan on when the humidity reaches a certain level.
Bathroom Fan Installation Tips
There are lots of great articles and videos that offer step-by-step installation tips. Here are some of the best ones we've found, along with advice on the most common problems you'll find related to poor installation techniques.
- Problem – The bathroom fan is usually placed in the center of the room which is wrong.
- Solution – The fan should be located over the major source of humidity, either the shower or bathtub.
- Problem – Too often, the fan is not properly vented to the outside. Most often builders only run the vent up to the attic where the moisture will damage the insulation.
- Solution – Proper venting of any exhaust fan should follow the straightest path to the outside. Elbows restrict the flow of air and if the vent isn't insulated, condensation can form (great illustration of a bathroom fan venting through the roof).
- Problem – When replacing a small fan with a larger one, you may need a larger hole or more support. We often ran into this problem with my handyman business (lots of older homes in southern New Hampshire), when the customer bought the new fan.
- Solution – Know the size of the fan's opening when shopping, whether it's hard-wired or using an outlet in the ceiling and whether it's supported on one or two ceiling joists. Be prepared to make adjustments to support the new fan.
Helpful resources I found while researching this article:
- How to Clean a Bathroom Exhaust Fan
- Troubleshooting Your Bathroom Exhaust Fan
- How to Repair a Bathroom Fan (video)
- How to Replace a Bathroom Fan (video) … but it doesn't cover venting through the roof so I'm still looking for a good video on this topic.
This is going to come in handy when we buy our home in the next couple of months. We don’t have a bathroom fan in our rental home, so it’s worth investing in one for our forever home.
I don’t really like the sound it makes but you gotta have it in your bathroom. I think this is an awesome guide. I really like that decorative light and fan in one.
Elizabeth, You don’t have to live with a noisy bathroom fan if you’re willing to replace it. Sadly builders look for every way to save & honestly, who tests the fans when buying a house … LOL!
Mine just fell out! Fell out!!! What a great post and some fab practical advice we all need – love it!
OMG, that is very scary. That means either the fan wasn’t secured well or you’ve got some serious wood damage up there, that the rot finally couldn’t hold the fan with it’s vibrations. Please, please be careful when you replace it.
I live in an apartment and never had to do this myself as the management usually takes care of it. But its always good to be in the know ;)
I never knew a bathroom fan could go out! I may need to check mine
I think my fan is going to be needing to be changed soon. It has been working hard the past few years.
Awesome tips! I always call someone to do these kinds of jobs, which can be costly. But, this detailed description makes something like this look pretty easy.
Thanks Toni, and nothing is ever as easy as we think. My goal is to explain enough that you can decide which projects to tackle yourself, and when to get help.
Thank you for this and I don’t have a bathroom fan but my mum does so I tell her this blog post tip .xx
Great useful tips! Thanks so much for sharing this!
Thanks for the tips. This is very helpful.
These are super helpful tips. Our bathroom fan is super loud, and it always bothers me (confession: sometimes I don’t use mine on account of the noise), also it doesn’t remove heat or moisture at all. I’ll have to keep these tips in mind to change out our fan and improve a few things.
Elisha, Maybe I didn’t put in my article that you should run the fan for 20+ minutes. If that isn’t getting rid of the moisture then maybe the fan isn’t hooked up to a vent to move it out … so check the article link I shared on fixing these.
Thanks for the tips and suggestions. We should be mindful of every detail inside our house. Awareness can set us free from harm and accidents.
Sarah-Louise, Love your comment & wish I could “like it” so now I’m wondering how long before that happens …
Thanks for this info. It is helpful post. I am thinking to change my bathroom fan as it is very noisy. This post will definitely help me.
We don’t have a fan in our bathroom. I want one, so hopefully someday my hubby will put one in.
Thank you for this! We actually might have to do this in our bathroom. The fan sounds weird.
My bathroom does not have a fan because it has a window. Strange that code allows that.