WebMaster, you said: Let’s be clearer.... two kinds of double wall: 1. Class A (CHimney) 2. Interior Double wall close clearance stovepipe. #1 can go through walls no problem as long as it meets the distance to combustibles. I suspect, although I don’t have any manuals handy, that #2 CANNOT pass through combustible walls. That said, your install may still be safe since you might be passing through a non-combustible wall and might still be maintaining clearances.... The reason that #2 would ne be allowed to pass through walls is that the exterior of said pipe can be plain black steel, which could rot (undetected) inside the wall. Also the clearances are usually further to this pipe - far enough that it would not properly fit between studs. Sounds like you are on the case. I'm wondering this: My pipe info. says: Close Clerance Connector HT and I am passing through one layer of Micore 300-as far as I understand this product it is non combustible. Like I said before-behind the micore is 3’x3’ of air space and the chimney connector. Do you still think it sounds like I am “on the case” or am I fired? Thanks so much for your help. I appreciate all of the expert advice-this stuff is like brain surgery to me. I’m trying to hang in there!