I plan to purchase a Rika Intergra II pellet stove insert. The unit is to be installed in the living room corner (approximately 97 inches wall to wall). I would like to vent straight thru the roof to get the best draw. The hearth is 18 inches above the floor and face of the wall to the ceiling is rock (2-3 inches thick). I do not have the room for a free standing pellet stove, the gas log units are zero clearance. What materials do I have my installation guy use to to pass inspection by the fire marshal and not burn down my new house. Thanks!