My preference would be to exhaust my bathroom fans directly through the exterior wall, to keep the ductwork very short, with the warm, moist air kept inside a conditioned space until exhausted outside. But the outside vent might be only 18″ or so below my soffit vents, and I’m concerned the moist air may be sucked up into the attic and condense under the roof. Is that a realistic concern?

Another option is to direct the exhaust ducts straight up through the attic, with the exhaust vent in the roof (with the ductwork in the attic well insulated). But I hate having yet another penetration in a roof that might leak at some point.

Third option is to run the ductwork up into the attic, and then horizontally over 14 feet to the gable wall. But that is a lot of ductwork to insulate, and the warm moist air is pretty much guaranteed to condense before reaching the exhaust vent outdoors.

What do you think are my best options here? I’m in a mixed humid climate in Virginia.