This is my first post but I have been reading the informative posts of others for several years now. Here is my predicament, I have an older home built in 1920, I installed a JotulF100 in the existing brick fireplace which has outside exposure on 3 sides. The first 4 feet of chimney was relined with flexible stainless steel liner (to bend around the smoke shelf) and then connected to rigid stainless steel liner to the top of the brick chimney. The brick chimney, being close to ninety years old, is looking a little worse for wear. Rather than tear the brick chimney down the the roof line, would thermix be a way to reinforce and at the same time provide some additional insulation to the stainless steel liner. The existing liner is uninsulated now but I have not had a draft problem in the 4 seasons that I have been burning. Thanks for your help. Eric in MT.