mjc1234

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.

glennjanie

Welcome MJC:
No, exhaust ductwork does not need to be insulated. I understand your concern about the extra humidity but it will be sealed in the duct to the outside; therefore, no porblem.
Glenn

mjc1234

Thanks for the quick response Glenn. I appreciate it. And thanks for saving me some work!

Mike

Hube

Anytime there is a difference in temperature between a pipe and the surrounding air there WILL be a risk of condensation/sweating.
An exhaust pipe carrying warm bathroom air thru a possible cold (winter time) attic area could condensate. Therefore, play it SAFE and insulate (fiberglass wrap) With no insulation on the pipe you could end up in time with a repair job to your bath room ceiling due to exterior pipe condensation seepage into the ceiling, plus possible mold in the attic.