Condensation On Attic Fan Damper

Exhaust fan condensation drip.

Condensation on attic fan damper.

The outside damper is stuck. If your ducts are properly insulated another potential cause of condensation is lack of use. 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. 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.

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. The exhaust vent in the powder room downstairs is fine this is a new thing. 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.

Whether you use your bath fan or not some warm air will still escape into the ducting. The attic is now pleasant as well just a few degrees warmer than the house. Find the vent hood on your roof or exterior wall. It should open only under pressure from the warm air to let it out and remain closed the rest of the time.

First inspect the damper on the outside. The duct is not kinked but there is a 1 5 inch gap between.