the install i will be doing will require me to connect class A to chimney liner. The local dealer showed me one and said it would have to be sealed off. I believe what was talking about was pouring the cement mix in the chimney with the liner instead of insulating the liner does this sound right as the filler will cost about 800 as aposed to 275 for insulation kit. here is a picture of what i have in the attic the red is the chimney and the line above is the roof line