Ceramic Insulation around chimney pipe at roof penetration -- is this OK?

[MaybeErnie]

I am concerned about cold air coming in at the big (12") hole where the chimney pipe goes through the roof. This opening is in a living space (actually a storage closet converted into a sauna) and is enclosed in a chase. I have double-wall Duratech pipe and have more than the required 2" clearance to combustibles. I bought some insulation labeled as "Ceramic Fiber Blanket Fireproof Insulation Baffle Rated to 2400F for Furnace, forging, Kiln and Stove" and am wondering if it is permissible to have that surround and in direct contact with the chimney. If not, what do you folks do to deal with cold air at the chimney penetration?

Mock up picture attached:

 

[begreen]

That looks like kaowool which is safe. A sheet metal block would seal better. It can be made in 2 pieces so that the chimney pipe doesn't need to be disassembled.

 

[bholler]

Technically if the chimney manufacturer doesn't allow for insulation it should not be there. That being said i see absolutely no way it could pose any risk so I would do it as well if it was an issue

 

[stoveliker]

I think a small length of pipe insulated is not a problem. I wouldn't do it if the insulation was a foot or so thick (and not allowed per mfg) as maybe things get warmer than designed at that point.

 

[MaybeErnie]

I actually didn't find any clear guidance about non-combustibles in the Duratech instructions. They're clear about the minimum 2" distance to combustibles, but I didn't see any mention of insulation. I may call Duravent support on Monday to run it past them.

That looks like kaowool which is safe. A sheet metal block would seal better. It can be made in 2 pieces so that the chimney pipe doesn't need to be disassembled.

I'm not sure what this "ceramic" insulation is actually made from. I'll see if there are more tech specs for it. I bought it through Home Depot but it was clearly drop-shipped from a different supplier.

And yes, sheet metal would definitely be better than the wire I put below the insulation. I was reluctant to fully enclose it until I get an inspection because I figure he'll want to see the roof penetration to be sure I have the required clearances. Once that's done, I'll try to do a better job with the insulation.

 

[bholler]

I actually didn't find any clear guidance about non-combustibles in the Duratech instructions. They're clear about the minimum 2" distance to combustibles, but I didn't see any mention of insulation. I may call Duravent support on Monday to run it past them.

I'm not sure what this "ceramic" insulation is actually made from. I'll see if there are more tech specs for it. I bought it through Home Depot but it was clearly drop-shipped from a different supplier.

And yes, sheet metal would definitely be better than the wire I put below the insulation. I was reluctant to fully enclose it until I get an inspection because I figure he'll want to see the roof penetration to be sure I have the required clearances. Once that's done, I'll try to do a better job with the insulation.

I would leave the insulation out for inspection. Not that they will know the difference