Let me preface this thread's question by saying I searched all around and added posts to slightly/somewhat/sorta related threads but still can't say I understand if its possible to safely seal and also safely insulate the space that's between the chimney pipe and the insulation shields? In my case I've managed to almost airtight seal the space (interior chimney chase) between the attic area and the living area by wrapping everything within the chase with cement board and then fiberglass taping and thinset sealing all joints between cement boards. But when I say I've sealed everything its really "everything except" the gap that goes between the chimney pipe and the insulation shields. Additionally I've managed to thoroughly insulate the transitions from living area to attic area where an average of R60 is everywhere except again the area the insulation shield sits. Now, I realize that the primary purpose of the insulation shield is to prevent the possibility of combustibles contacting the chimney pipe so I'm not trying to defeat that purpose in any way whatsoever but what I'm wondering is can I safely put something like high temp silicone sealant on that gap that goes around the chimney and can I safely put something like Rock Wool, or Roxul or something else specific in that space around the chimney to further insulate things? If this is one of those things where you just forbid yourself from altering the original state of things, that's totally fine for me; I just don't know so I'm asking the experts. I'm hoping that at the least it is okay to high temp silicone seal the gap that goes around the chimney though because that's basic air sealing? Anyways, thanks in advance for advice.