I am working on a kitchen remodel and installed a large exhaust fan, with 10″ ducting.  I may add makeup air at a later date, since the fan goes up to 1300cfm, but for now need to get the vent installed.

My plan was to run the 10″ rigid ducting straight up through the roof.  Seems simple enough; I have a metal roof, so will have to make some cuts up there, and add flashing…all seems okay.

But I’m unsure about which duct to buy.  I’d say any from FAMCO would be fine.  I live in a cold climate, and we get a lot of snow (Maine).  I can rake the roof, which I already do anyway.  But I’m thinking I’d want a taller exhaust vent that doesn’t get buried in snow.

Except for the fact that condensation would be an issue–a taller vent would easily cause the exhaust to condense in the winter, assuming no vent would be insulated on the exterior.

I’m thinking to prioritize any water issues, insulate the duct in the attic (which will also be hot roof soon).  On the exterior, use a lower profile vent to minimize cold surface area. 

Perhaps install an additional damper before the exterior vent to avoid issue with cold backdrafts.  Although I’d imagine the air flow is following a stack effect, and shouldn’t be an issue.

Am I overlooking any codes?  Does this all sound coherent or am I missing something.

This could be a great topic for FHB to write about in one of their articles.  I haven’t seen any on this issue.