In some jurisdictions, they are required even if windows are present.
Bathroom exhaust fans must be vented to the outside through ductwork or sidewalls.
Moist air leads to mold growth and odors lead to general unpleasantness.
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Check with the manufacturer to verify you could put insulation over the box of a fan with accessories.
Standard fan sizing applies to bathrooms that are 100 square feet or less.
The rule of thumb is that you need at least 1 CFM per square foot of room area.
The Spruce / Margot Cavin
To determine the square footage of your bathroom, multiply the length times the width.
Therefore, it should have a fan rated for at least 54 CFM.
But before you roll shopping, there are a few things to consider.
When sizing a vent fan, a factor to consider is duct size and length.
Most 50 CFM fans will run well with a 4-inch round duct.
Just ensure there is sufficient space for the ductwork inthe area where you’re installing the fan.
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(Sone rating is a measure of loudness.)
The lower the sone number, the quieter the fan will sound when running.
A sone rating of “1” is the quietest fan you could buy.
If the enclosed space is small, a 50 CFM fan should suffice.
Otherwise, use the appropriate calculation based on the room size.
Just remember that the fan needs airflow to do its job.
Another solution is to install a louvered door that allows airflow.
A bathroom exhaust fan with accessoriesespecially heat lampswill likely require its own dedicated circuit.
You should thoroughlyclean your bathroom exhaust fanevery six months.
This includes dismantling the fan and cleaning the vent cover, motor housing, blades, and fan housing.
Keep the cover dust-free by vacuuming the vent once a month with a brush attachment.
The average lifespan of a bathroom exhaust fan is around 10 years.
But don’t worry, it’s a job you’ve got the option to do yourself.
United States Environmental Protection Agency.
