Condensation On Attic Fan Damper

First inspect the damper on the outside.

Condensation on attic fan damper.

Attic air leak into the fan unit unitself from not being well sealed to the ceiling attic floor exhaust damper not opening properly so humid exhaust air doesn t exhaust and stays in the duct getting cold enough to condense and drip back down. If your ducts are properly insulated another potential cause of condensation is lack of use. Exhaust fan condensation drip. If water drips from the bathroom exhaust fan the damper that normally controls the flow of air through the pipe may not be working correctly.

Whether you use your bath fan or not some warm air will still escape into the ducting. It should open only under pressure from the warm air to let it out and remain closed the rest of the time. Bath fans have a damper designed to keep the outside air from entering in through the fan but that valve doesn t stop warm air from escaping. The damper will help prevent cold air from dumping back down into the house which may lead to condensation right at the fan itself.

The duct is not kinked but there is a 1 5 inch gap between. Just as we were ready to move back in we discovered both bathroom fan exhaust ducts as well as the gas dryer duct all upstairs have been filling with condensation. There s a damper on the fan housing too but the outside damper is much more likely to stick. If the damper won t open the fan may drive enough air through the duct to cause condensation but not enough to warm the duct and dry it out.

Find the vent hood on your roof or exterior wall. The attic is now pleasant as well just a few degrees warmer than the house.