How to connect vent duct to roof jack?
We are going to have a 10" round duct installed from our kitchen vent hood and it will exhaust thru the roof. I can't find a roof jack off the shelf anywhere that will fit that large a duct, so we might end up getting one made. So, I don't know what size to make it, and I think it depends on how the duct is attached to the roof jack. The roof jacks I've seen are tapered, wider at the bottom than the top. One person suggested that the *top* of it (the narrow end) should be 10" so you can attach the duct there. Someone else said it should be 10" at the bottom and narrow to 8" at the top.
So, having never attached a duct to a roof jack...how do they normally attach, and what size does it need to be? It's a smooth metal duct.