I am considering buying a hearth stone heritage. I am new to wood heating. The stove install requirements has 16 and 15 inch set backs from a combustible wall. My plan is to use metal studs, but micor 300 and then cement board and tile on the walls with an inch airspace to make them non combustible. However, the Hearth stone gives no change in set backs for combustible or non combustible walls. The jotul setbacks does? Any ideas if I can reduce the side set backs if its a non combustible wall?