So I installed a new insert and liner last August for my house. I had been told that since it was an exterior chimney and that the clay liner was in good shape that I would not have to insulate the liner. I had no problems last burning season but have since decided after doing more research that I should insulate the liner. After speaking with a chimney sweep they said that since I have a flex liner that they would not be able to pull it out and just re-line that one. Also since I have a 8 x 13 flue, that inorder to get a new insulated liner down the chimney, that the clay tiles will have to be removed in order for it to fit. Has anyone else had this problem? Would the pour in mix be a better remedy? Any help would be appreciated, thanks.