First time seeing this configuration for a 20190904_093019|651x500 gas furnace and water heater venting through a metal B-vent installed on the exterior of the home. Does the 2 foot 10 foot clearance rule apply? and is there a clearance from grade.
My thought is the stack will cool in the winter time (allowing combustibles to become heavy) and backdraft. Water heater with draft hood (Rheem) ,mid efficiency furnace with induction fan (ruud) could not find any information in manuals
I have only seen this configuration for pellet stoves and boilers