Moist indoor air condenses inside a cold uninsulated duct and water runs down into the fan.
Bathroom vent leaking moisture into attic.
In winter when the warm moist air from the bathroom hits cool air in the attic or outdoors it condenses sending drips back down the ductwork.
Obviously condensation dripping from the nails and sheathing is not a good thing.
The cause of condensation.
The hot and humid summer air will condense when it hits the pipe made cold by the air conditioning system.
If bath fan ducting isn t properly insulated the moist air from your house will condense inside the duct.
If you vent the bathroom exhaust fan to close to the soffit vents which are vented plates under your homes outer edge and roof your home the air can be sucked right back into the attic from the soffit.
This can also happen during the warmer months.
The usual cause is condensation inside the duct.
This can be the nails the sheathing the rafters and more.
In summer humid outside air condensed on a pipe cooled with air conditioning will drip when humid bathroom air adds to the moisture level.
On a cold day the moisture in the air will condense on anything below the dew point.
No you cannot vent the bathroom exhaust fan into the soffit vents.
The duct boot needs to be properly sealed so cold air won t escape.
When cold air mixes with humid air that s when the condensation and moisture occurs.
Bathroom exhaust fans perform an important function by removing excess moisture from your home.
The most common sign of your ac leaking water is water stains or yellowing on your ceiling near the air vents not a good look.
The fan pulls warm moist air from the bathroom and distributes the air to the attic.
Water stains on the ceiling around your bath fan may indicate a leak coming from the vent cap on your roof but condensation is the more likely culprit.
The water could be coming from an air leak in the vent or something called the duct boot.
This meetup leads to condensation and will drip water back to your bathroom.
If your bathroom fan exhausts into your attic and not outside of your home you could start having serious issues with moisture and mold.
Condensation from moisture laden air can cause health and structural problems as well especially when the bathroom vents discharge moist air into attics or crawl spaces.
You should never have a bathroom vent terminate in your attic it must exit your roof directly and ideally be far away from soffits and roof overhangs which could retain the moisture and divert it.
Leaking and damaged vents as well as improperly installed ones also can cause problems.
When venting a bathroom exhaust fan make sure to vent the air to the outside rather than into your attic where it can cause mold and mildew to form.
