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."

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Eric Barker
Moraine Woods Consulting, Inc.
Barrington, IL