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Chimney and ceiling insulation

user-1137156 | Posted in General Questions on

I’ve been struggling with how to “legally” and safely get a class a chimney through r80 insulation in a ceiling The listed hardware only accommodates 10″ of insulation above framing. Is the only alternative build a plywood box (chase) that provides 2″ clearance around the chimney from ceiling to roof? Would an 8 sided duct made of duct board be a safe and legal “chase”? Can the “chase” end short of the roof?

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  1. davidmeiland | | #1

    It may depend on the pipe manufacturer you choose. I just installed ICC Excel class A woodstove pipe through 20" of cellulose. There is a ceiling support piece that handles the first 10" or so, then an extension above that for the rest. On top of the extension is a storm collar (inside the attic) that keeps insulation from falling down into the air space.

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