I just rebuilt my chimney. I have a 50 gal natural gas water heater in the basement. It used to be vented just in the terra cotta flue. That wrecked the flues of course. Now the chimney is about 15 feet of cotta flue then an open chimney the last 9 feet. So I am looking at relining with the duravent aluminum liner kit. Will I be ok code wise to just run the liner without insulation? I can't find it specifically listed in any literature. Thanks!