Condensation On Attic Fan Damper

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.

Condensation on attic fan damper.

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. The outside damper is stuck. The duct should not be aimed at a roof vent or have any loose.

There s a damper on the fan housing too but the outside damper is much more likely to stick. The duct is not kinked but there is a 1 5 inch gap between. First inspect the damper on the outside. 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.

It should open only under pressure from the warm air to let it out and remain closed the rest of the time. If your ducts are properly insulated another potential cause of condensation is lack of use. The exhaust vent in the powder room downstairs is fine this is a new thing. 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. The damper will help prevent cold air from dumping back down into the house which may lead to condensation right at the fan itself.