Bathroom Exhaust Fan & GFCI Bathroom Vent Protection Requirements

Every bathroom without an openable window (min 1.5sq. ft) requires an exhaust fan.


Every bathroom without an openable window (min 1.5sq. ft) requires an exhaust fan.Bathroom vent improperly discharging into the soffit resulting in mold growth

Bathroom vent discharging into the soffit which is not recommended

The bathroom ceiling exhaust (or wall) should be discharging to the house exterior, not into the ceiling / wall frame cavity, or another room, crawlspace, attic, etc. This is extremely important if your bathroom contains any significant humidity source like a shower stall, bathtub, steam shower, etc. Discharging moisture from your bathroom fan into some enclosed and/or poorly ventilated areas is often responsible for the crawlspace and attic mold growth. By the way, have you ever checked your attic ventilation?

Bathroom vent improperly discharging into the attic

  • Bathroom ceiling exhaust fan requires a damper to prevent back-drafts
  • Bathroom exhaust exterior vent opening should be screened with a ¼” to ½” mesh to prevent birds from building nests inside the vent pipe

GFCI protection for bathroom ceiling exhaust ventBathroom vent GFCI protection is required for installations above the shower or bathtubNEC (National Electrical Code) does not require bathroom exhaust fans to be installed on a GFCI protected circuit. However, you should be following the manufacturer’s installation instructions. In most, or should I say in all, cases concerning a bathroom exhaust fan installation directly above the bathtub and / or shower stall (or any other moisture sources), the bathroom fan must be listed as suitable for such locations and must be installed on a GFCI protected circuit.

This is a paragraph from the bathroom exhaust fan installation instructions:

“If this bathroom exhaust fan is to be installed over a tub or shower, it must be marked as appropriate for the application and be connected to a GFCI (Ground Fault Circuit Interrupter) protected branch circuit.”Bathroom vent - GFCI protection requirement for over the shower and tub installationsTo test if a bathroom exhaust fan is GFCI protected, turn the fan ON, and push TEST button on a bathroom GFCI receptacle or GFCI breaker dedicated for this bathroom. If the exhaust fan is still running after the receptacle or the breaker tripped, it is most likely not protected (there are occasionally some hidden GFCI receptacles installed).

You should always check the manufacturer tag before attempting to install a ceiling exhaust fan directly above the bathroom tub or shower stall.

Bathroom exhaust fan tips:

Bathroom vent - humidity sensing fan with time and sensitivity adjustment

  • For those who always forget to turn ON the bathroom exhaust fan (or forget to turn it OFF), I highly recommend one with a humidity-sensing switch. I’ve been using two of those in my bathrooms for almost 4 years, and I am very happy with their performance. One of the humidity sensors failed during the first year, but the manufacturer replaced it without any problems.
  • Bathroom humidity sensing fan (at least the one that I have is made by BROAN) can be wired like a 3-way switch – it means that you can turn the fan ON/OFF using a regular wall switch or it will be automatically activated by an elevated humidity level.
  • Controls on the bathroom humidity-sensing fan allow for the time of operation and humidity level adjustments.

Let me know if I’ve left anything unanswered about bathroom exhaust fans!

  1. Rhonda says

    Question about this entry:

    What should the clearances be for the exhaust pipe? (How far should it be from the roof/wall and openings?) Thanks! 🙂

    1. CTH Experts says

      Hi Rhonda,
      Some jurisdictions allow soffit installations (might have a 4’ clearance from the window restriction), some don’t (even if they do I wouldn’t install your bathroom exhaust discharge port in the soffit / moist, warm air could travel back into the attic). Roof termination is commonly used but the vent might get covered with snow (if you get significant amounts of snow during the cold season). Other restrictions that may or may not apply in your location; house side wall installation at a minimum 3’ distance from the soffit and at least 4’ horizontally from any operable wall openings – windows, doors. 3’ distance (I’m not sure about that 3′) from wall and roof passive vents (attic, soffit, crawlspace, and basement) to prevent moisture penetration. In some cases it might be simply impossible to choose a bathroom exhaust vent termination point installation that complies with those requirements so explaining it to your local building inspector would be the best solution.

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