Perlite and liner question

[Fluke216]

I’m putting a concrete cap on top of an existing masonry chimney. This chimney has 3 8 in clay flues. I lined one preciously with a 6in flex and insulation blanket. I see during the old cap removal that all three flues are surrounded by perlite. I was planning on lining the other flue and capping the one off in the middle still having an option of utilizing it if needed for something in the future. Question is is it necessary to use the insulation blanket on the liner since the outside of the flue is already insulated with perlite. The blanket makes it really tight so I wanted to avoid that maybe could dump that insulating mix down for a little extra insulation. Just wanted to get some opinions. Thanks

 

[Ctwoodtick]

I’m not a pro but I would wonder if the perlite is actually giving you zero clearance where you need it and how evenly distributed it is going down the chimney. I would do the blanket insulation so you know that you are good.

 

[begreen]

Unlike flex liner, flue tiles are rigid, so having 1+" insulation all around is possible. If the perlite is even, all around the flue tiles, then I think an uninsulated 6" liner will be ok.

 

[bholler]

I would say technically it wouldn't meet code because the perlite isn't a listed liner insulation. But practically I can't see that there is any danger. I would probably still pour insulation mix around it though just for good measure

 

[Fluke216]

I would say technically it wouldn't meet code because the perlite isn't a listed liner insulation. But practically I can't see that there is any danger. I would probably still pour insulation mix around it though just for good measure

Yea thanks I think he installed perlite as he built it not sure. But the other flue was only about 25’ and I had a tough time with the insulation this ones longe and I can see it not strait so I think I’ll do un insulted and then add the mix after.

Unlike flex liner, flue tiles are rigid, so having 1+" insulation all around is possible. If the perlite is even, all around the flue tiles, then I think an uninsulated 6" liner will be ok.

Ok thanks that’s what I was thinking.

 

[Fluke216]

I would say technically it wouldn't meet code because the perlite isn't a listed liner insulation. But practically I can't see that there is any danger. I would probably still pour insulation mix around it though just for good measure

Unlike flex liner, flue tiles are rigid, so having 1+" insulation all around is possible. If the perlite is even, all around the flue tiles, then I think an uninsulated 6" liner will be ok.

Is chimney mix the only thing that's going to be listed to pour down between the liner and the terocctta tiles? I've read older threads about people using perlite and or vermiculite I assume like you said those are not listed options and not a good idea? any info is great guys thanks

 

[bholler]

Is chimney mix the only thing that's going to be listed to pour down between the liner and the terocctta tiles? I've read older threads about people using perlite and or vermiculite I assume like you said those are not listed options and not a good idea? any info is great guys thanks

Yes raw perlite or vermiculite are not listed and shouldn't be used. They used to be used allot but we learned that they settle over time and aren't effective

 

[Fluke216]

Yes raw perlite or vermiculite are not listed and shouldn't be uses. They used to be used allot but we learned that they settle over time and aren't effective

ok thanks

 

[Hoytman]

Yes raw perlite or vermiculite are not listed and shouldn't be used. They used to be used allot but we learned that they settle over time and aren't effective

Doesn’t the Thermix have vermiculite in it? Rockwool in it? Of course it’s mixed with water right?

Do you think it insulates as well an insulated liner? I suppose that would determined by the thickness it’s poured around a liner, but lets say all things being equal.

 

[bholler]

Doesn’t the Thermix have vermiculite in it? Rockwool in it? Of course it’s mixed with water right?

Do you think it insulates as well an insulated liner? I suppose that would determined by the thickness it’s poured around a liner, but lets say all things being equal.

Thermix and the other mixes are a blend of vermiculite and cement. It needs to be 1" thick to be equivalent to wrap