Hi All - I am in the process of putting in a new bathroom ventilation fan and I have a question about insulating the ductwork. I snaked some semi-flexible duct through an adjacent attic and out the roof. The total length is around 7 or 8 feet. Was wondering if it is necessary to insulate the ductwork in the attic? The guy at the plumbing supply store told me "no" but thought I would check here as well. Not insulating sort of makes sense since it's not like a dryer where you have the potential of hot air passing through a cold attic. However the bathroom will have a whirlpool tub and shower so there is humid air that will be traveling through the duct. Just want to make sure I am not causing problems by not insulating. Any advice you guys can give would be greatly appreciated. Thanks in advance.