An attic insulation shield is required. This part can be purchased from the chimney pipe manufacturer (metalbestos 6T-AIS). Being that most pipe has a 2" clearance, can this sheild be comprised of a "wood framed box" or "sheet metal guard", instead of the AIS? Being that you can run a chimney, thru a "chase", I would think that this would be acceptable. (I have a vaulted ceiling making it difficult to use the AIS and I don't want to use a "support box" if possible)