I have a house built in the late 80's in western NC. The chimney is constructed of wood on the outside with a straight pipe liner. I'm not sure if it's aluminium or steel. The pipe is 8" diameter so there is room for a 6" liner, but is it necessary? How would I tell? There is an old heatilator insert in there right now with some type of stone liner about 3/4 inches thick in a sheet metal box. I'm trying to figure out if I will be able to put a small wood stove insert into this heatilator and if I will need a liner or not. Any help would be much appreciated.