Are the flue liners the same for both natural and direct vent models?
No. A natural vent model will have a single four-inch round vent on the top center portion of the insert. While in operation, these units will use room air for combustion and flue gases in turn rise up the single flue liner. A direct vent unit will have two three inch round vents on the top portion of the insert. One flue liner will draw fresh air in from the termination point and the adjacent second flue liner will exhaust flue gases.
