Symptoms
- Mirror stays fogged long after showering
- Visible condensation on walls and ceiling
- Fan runs but seems to move little air
- Musty smell developing in the bathroom over time
Likely causes
- CommonDust and grime clogging the fan's intake grilleFans rarely cleaned lose much of their airflow capacity from a dirty grille and blades.
- CommonFan is undersized for the bathroom's square footageA fan rated too low in CFM for the room size will always struggle to clear steam adequately.
- PossibleBlocked or crushed exhaust ductFlexible ducting in the attic can sag, kink, or become blocked with debris, restricting airflow even if the fan itself works.
- Less commonDuct venting into an attic instead of outsideImproperly installed ducts that dump moisture into the attic instead of outdoors won't clear the room efficiently and cause other problems.
What to do
- Turn off power to the fan at the breaker before cleaning.
- Remove the grille cover and vacuum out dust, then wipe down the fan blades and housing.
- Turn power back on and check if airflow noticeably improves.
- Hold a piece of tissue near the grille while running to gauge suction strength.
- If accessible, check the attic for the duct run, looking for kinks, sagging, or disconnections.
- Straighten or support sagging flexible duct, and reconnect any loose sections with foil tape and duct clamps.
- If the fan seems weak even when clean and the duct is fine, consider it may be undersized and worth upgrading to a higher-CFM model.
Tools and parts
- Vacuum with brush attachment
- Flashlight
- Foil tape (if duct repair needed)
Bathroom exhaust fan (higher CFM)Search: “bathroom exhaust fan CFM”
When to call a pro
Call an electrician or HVAC technician if the fan needs replacing or the duct routing needs significant rework.
Safety
Use caution
Always cut power at the breaker before removing the fan cover or touching wiring.