A question for the experts here. A masonry chimney, oftentimes get a SS liner installed for a new stove/insert install. This liner, to meet code must be insulated, correct? Why is this the case, whereas previous to the liner install one would use the fireplace and have direct flame/smoke exhaust on the clay chimney tiles without safety issue, assuming the chimney is in good shape. It seems like a SS liner, insulated or not is one extra layer of protection? What am I missing? Thanks!