With the exception of the one warm week-end this winter, I've been burning 24/7 since 11/30/07. I looked in the attic and discovered the first section of double wall ,which is connected to the stove pipe adapter, had discolored to an black anodized look. The piece directly above, which passes through the flashing, looks new. I understand this first section takes all the heat, but should the outer wall change colors?. The entire chimney and adapter, heat shield, support, etc. came together as a kit from Supervent and I'm confident it was installed correctly. Do I have a warrenty issue or is this normal? My stove is medium-sized ( 2.3 cu.ft.) and truly has not been fired over 475 F for over 20 minutes. Here is where I use the "n" word...newbie..so thanks in advance for your help.