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.
|Minimum Ventilation (CFM) Required
|50 sq ft
|50 to 100 sq ft
|1 CFM per sq ft
|Add up CFM requirements for fixtures:
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:
|Noise Level (Sones)
|Typical office noise
|Quiet fans rated 1.0/less 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.