Chimney construction vermiculite

[Ctwoodtick]

I think I know the answer to this but, was vermiculite ever commonly used as an insulator in masonry chimneys between the clay liner and chimney chase? I believe it’s supposed to be only an air space back there but wanted to ask. Thanks

 

[bholler]

I think I know the answer to this but, was vermiculite ever commonly used as an insulator in masonry chimneys between the clay liner and chimney chase? I believe it’s supposed to be only an air space back there but wanted to ask. Thanks

It is not terribly uncommon. But also not recommended for the same reasons straight vermiculite shouldn't be used around as liners

 

[Ctwoodtick]

It is not terribly uncommon. But also not recommended for the same reasons straight vermiculite shouldn't be used around as liners

Thanks for the response. Reason I ask is because a couple years ago, I had the clay liner broken out of my masonry chimney built in 1977. This was done by a pro to make room for a new insulated ss liner for wood insert. Chimney has 2 clay liners, one of which is not in use. I have no idea if there was vermiculite in the airspace that was broken out, but had read that sometimes vermiculite was used in chimney applications. I know that vermiculite from the time my house was built often contained asbestos. I don’t have a blockoff plate in the damper area above the insert at this time. Wasn’t sure if any possible vermiculite remnants could still be in chimney (if they were ever there to begin with). My wood insert surround, as expected, does not make an airtight seal to masonry and there are small gaps in the sheet metal shroud of insert where dust, etc could theoretically get pulled in and blown out into room by blower. Again, not sure if the chimney ever contained vermiculite, but should I be doing anything about this, or am I just way overthinking the whole thing? Thanks

 

[bholler]

Thanks for the response. Reason I ask is because a couple years ago, I had the clay liner broken out of my masonry chimney built in 1977. This was done by a pro to make room for a new insulated ss liner for wood insert. Chimney has 2 clay liners, one of which is not in use. I have no idea if there was vermiculite in the airspace that was broken out, but had read that sometimes vermiculite was used in chimney applications. I know that vermiculite from the time my house was built often contained asbestos. I don’t have a blockoff plate in the damper area above the insert at this time. Wasn’t sure if any possible vermiculite remnants could still be in chimney (if they were ever there to begin with). My wood insert surround, as expected, does not make an airtight seal to masonry and there are small gaps in the sheet metal shroud of insert where dust, etc could theoretically get pulled in and blown out into room by blower. Again, not sure if the chimney ever contained vermiculite, but should I be doing anything about this, or am I just way overthinking the whole thing? Thanks

You should install a blockoff plate but not for that reason. And yes you are over thinking it lol

 

[Ctwoodtick]

Thank you for the info, I have been thinking about doing an after the fact blockoff plate. The damper frame is still in place in the fireplace but I think that I could install block off plate lower that that, right? Also, you said that you see vermiculite sometimes in masonry chimneys. Just curious about how frequent you might see that (1 percent of the time, 10 percent of the time?). Thanks again

 

[SpaceBus]

For what it's worth to you my 1975 interior masonry chimney does not contain vermiculite.