Bathroom Duct To Attic Gable Vent

Crawling in the attic revealed the connection of four bath fans into one long duct going to a gable vent.

Bathroom duct to attic gable vent.

First off you ll be reducing the size of the gable vent. The resistance to the airflow in the long duct caused the air to back up in the nearest bathroom especially when more than one fan was on at the same time. Bathroom exhaust venting does not have to exit up through the roof and in fact that s not necessarily even the best termination. The best way to vent bathroom fans is with schedule 20 bell end drain pipe.

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. No you cannot vent the bathroom exhaust fan into the soffit vents. 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. The bathroom exhaust ventilation fan disperses air through an opening in the fan housing which is usually 3 inches in diameter and ideally faces in the direction of the ventilation system outlet.

Depending on how the attic ventilation is designed the hot moist air exhausted from the duct could be drawn back into the attic through the gable vent. And of course a bathroom with a window doesn t require an exhaust vent. An exhaust vent fan can exhaust out through a gable end side wall or out through a soffit overhang.