Originally Posted by
Eric Barker
I was not able to open Billy's attachment so I'm commenting without knowing what was in it. No single wall vent should be used outside of the appliance's room or area. Also, I see no flashing detail where the vent penetrates the roof.
One other comment - it's commonly misused but the "flue" is the space inside the vent or chimney liner. It's not a component or "thing."
Eric--Guilty as charged on the misuse of "flue." However, it's what my clients understand. When I talk about vents they seem to think in terms of intake, not exhaust, so I've gotten sloppy. I should have known better than to post the question that way here.
The flashing is fine at the roof; it's a soldered galvanized base similar to a plumbing roof jack. No problems there.
The Simpson info Billy posted (thanks, Billy) gives their blessing to a similar design. It shows the top of the B vent section ending about 1.5" to 3" above a base flashing. There is no base flashing in my example, but the overall concept is similar. Seems strange to me, but the double wall does not have to extend to the top.