Bathroom Exhaust Fans

While many local codes allow for bathroom exhaust fans to discharge into the attic and/or at a soffit, roof or other vent, this practice is no longer considered acceptable. Both the EPA and the American Society of Home Inspectors now consider this a defect. In addition, the manufacturers of Bath Exhaust Fans provide specific installation guidelines which recommend that they be vented directly to the exterior through a dedicated vent.

What is the definition of a “Dedicated Vent” and why is this important?

A dedicated vent is one that is specifically designed for and only used for one purpose. Very often the vent has a built in flap that allows airflow out but not back in. An existing roof, gable or soffit vent is not designed or specifically intended for this application. These vents are meant to provide proper airflow throughout the attic. Blocking any of these vents with bathroom vent pipes restricts the intended airflow. This can lead to back drafting and/or premature deterioration of the roofing surface due to interior temperatures and humidity. In addition, the warm moist air that is discharged through the pipe can cause wood rot and fungal growth. This can result in structural integrity issues and potential health risks.

Below is an example of how a typical bath exhaust fan is vented through a roof.

Resources

• Mold
• Selecting a Mold Remediation Contractor
• Roof Information
• Inspecting a Septic System
• Exterior Insulation & Finishing Systems
• What is an ERC Property Assessment
• Bathroom Exhaust Fans
• Arc Fault Circuit Interrupter (AFCI)
• Underground Storage Tanks