Question: Installing a VC Encore into a 6" metalbestos flue. It's a straight run inside thru the roof--22' total. A 3.5' run of double wall pipe from stove to metalbestos start. This is a 'cathedral' ceiling rig. Question: the Vermont Castings specs give an option for the Encore to go into a 6" flue but no fireplace operation possible. A 6" pipe adaptor is available. Any problems with this? I get opinions all over for the operation of the Encore as a heater only. Thx. Answer: Technically Vermont Castings has approved the stove for 6" operation only when the door is closed. I personally have concerns of using this particular unit in this manner. I suggest you install 8" then you would be able to have the open fire you desire.