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Meeting Bathroom Ventilation Requirements

New Construction Homes

Did your builder provide CFM testing for bathroom and laundry ventilation systems? Did they pass the required 50cfm?

I doubt you can answer those questions because most builders do not test these for code requirements. But don't fear we can handle this for you.

 We offer complete exhaust CFM verification for both new construction and pre-existing Residential and Commercial buildings. Without proper ventilation, your home can develop mold issues. Testing your exhaust systems is a must to insure your home has proper ventilation.

home energy auditBathroom vent fans are required by the NEC (National Electrical Code) and local building codes for any bathroom that doesn't have a window that can be opened to provide ventilation. In some jurisdictions, they are required even if windows are present.

A vent fan does two important things:

It removes hot, moist air, and it can remove odors. Moist air leads to mold growth, and odors lead to general unpleasantness.

But installing a weak, undersized fan is almost not worth the effort, even if the fan meets the minimum requirements. It's important to understand how vent fans are sized and how to choose one with the proper capacity for your space. Testing the fan after installation is needed to ensure it is actually providing the needed cfms. 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. But as you get up into the higher CFM fans, duct size will have to be increased to 5- or 6-inch round duct. The length of run, as well as the number of fittings, elbows, etc., will also affect the amount of air your duct can effectively carry.

Bathroom Size Minimum Ventilation (CFM) Required*
Less than 50 sq. feet 50 CFM
50-100 sq. feet 1 CFM per square foot of floor space
More than 100 sq. feet Add the CFM requirement for each fixture:
Toilet 50 CFM
Shower 50 CFM
Bathtub 50 CFM
Jetted tub 100 CFM

*Note that these rates represent a minimum requirement. Higher ventilation rates are also acceptable and will have a minimal energy impact.

Other ventilation considerations include:

  • An enclosed toilet should have its own exhaust fan.
  • Fans approved for installation in wet areas should be located over (or very near) the shower or tub when possible.
  • Bathroom doors should have at least ¾" clearance to the floor to allow for proper entry of makeup air.
  • Bathrooms with greater than an 8' ceiling may require additional ventilation.

Call us today at 425.608.9553bathroom ventilation