Vermiculite/Perlite for chimney insulation: Can I use gardening type or must it be masonry fill typ

[staceyneil]

I have another thread about our chimney lining/insulation project but thought I'd post this specific question here in case others are looking for the answer, too

We're lining an interior masonry chimney with SS liner (not technically necessary but we're doing it anyway.) We do not NEED to insulate the chimney, but plan to use Kaowool at the bottom block off plate and also stuff some down the top of the chimney as far as we can reach.

We're considering also filling the rest of the chimney with Perlite of Vermiculite. I have found several types, sizes, and grades. A local masonry supply place sells VERY FINE perlite for filling masonry walls. I would rather use a coarser material that's less likely to sift through teeny gaps we might miss.... the horticultural type -for seed-starting- is much coarser, and also easier to get locally. Is it safe to use that stuff?

Thank you!
Stacey

 

[laynes69]

Its all fireproof. I used the course that I got through the local concrete supply. I think it could be used in gardening for ours isn't treated for water. If the chimney is in good shape along with the liner, there shouldn't be any worries for moisture. If your worried about moisture retention, go with perlite.

 

[branchburner]

If your worried about moisture retention, go with perlite.

Or else make sure the vermiculite has been treated with silicon for water resistance. Treated = construction grade, non-treated = horticultural grade. If there is concern about it sifting through any cracks, I think you are wise to go with the coarser material. And even if there is little chance of water penetration, I also think it is wise to use a material that will not expand with moisture.

 

[oconnor]

Stacey

I may have mentioned this in your other thread before, but it merits repeating. Make sure you use the material that your liner manufacturer states is appropriate for their product. You are playing with fire here, literally, so it's really worth playing by the rules. There are lots of places in life worth taking shortcuts to save money, but chimney liner installations aren't one of them.

You mention that you don't need to insulate, so I assume that means you discovered that your chimney has 2 inches of air gap around it all the way up. If you do have that, then there is no need to insulate for performance with an interior chimney.

So why are you insulating?

 

[staceyneil]

Thanks, guys...
Brent, We just figured it might help the stove draw better and decrease creosote build-up, especially at the top where the masonry chimney runs outside the house.....
The sweep who was here the other day said he wouldn't insulate at all, but then again he also said he didn't see anything wrong with just sticking a short piece of liner up through the flue and calling that good...
We're now leaning towards just insulating the block off plate at the bottom, and stuffing some kaowool down as far as we can from the top.
Thanks-
Stacey

 

[firefighterjake]

Thanks, guys...
Brent, We just figured it might help the stove draw better and decrease creosote build-up, especially at the top where the masonry chimney runs outside the house.....
The sweep who was here the other day said he wouldn't insulate at all, but then again he also said he didn't see anything wrong with just sticking a short piece of liner up through the flue and calling that good...
We're now leaning towards just insulating the block off plate at the bottom, and stuffing some kaowool down as far as we can from the top.
Thanks-
Stacey

I'm thinking it's time to look at another chimney sweep . . . and hopefully the sweep you had is not associated with the Maine Association of Chimney Service Professionals.

http://meacsp.org/