# Can I used bagged vermiculite as chimney insulation?



## rfalk (Feb 26, 2008)

Hi, I am in the process of purchasing a Lopi Declaration insert. My existing stone chimney is 30-35' tall (old English Tudor). I am planning on installing 6" SS flex liner, even though the chimney is already lined with 12x12 chimney tile. I'm wondering if after I install the blockoff plate and liner if i can just purchase loose Vermiculite insulation and pour down the chimney around the liner? Most online chimney stores carry a vermiculite insulation that you mix with water and pour down the chimney ($50+ per bag, plus shipping)....loose Vermiculite from a box store is significantly cheaper. Anybody know if there would be a problem doing this? Thanks, Bob


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## milner351 (Feb 26, 2008)

Bob

I've been thinking something similar - but using the vermiculite between the two steel layers of my heatilator....

Where are you finding vermiculite at the big box stores?  I looked and looked this past weekend for ANY high heat insulation and came up empty.

There is also vermiculite for gardening..... is that the same stuff we need?


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## Mmaul (Feb 26, 2008)

I was wondering the same thing I did find some this weekend at Menards.


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## rfalk (Feb 26, 2008)

I purchased Vermiculite at Menards.....used it for filling some spaces in my attic a few years ago..has about a R 3 insulation rating. It's rock essentially, mined right out of the ground. Low density, so works as insulation. Pours easily. Fairly cheap...I seem to remember I paid around $5-$7 bag... bob


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## Jay H (Feb 26, 2008)

rfalk said:
			
		

> I purchased Vermiculite at Menards.....used it for filling some spaces in my attic a few years ago..has about a R 3 insulation rating. It's rock essentially, mined right out of the ground. Low density, so works as insulation. Pours easily. Fairly cheap...I seem to remember I paid around $5-$7 bag... bob



I believe Vermiculite is added to potting soil to retain moisture because it naturally absorbs moisture from the surroundings..

Does the added moisture affect it's R value??? 

Jay


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## rfalk (Feb 26, 2008)

Most insulation looses R value when wet.....It would be important to keep it dry, but I would think a hot pipe running through the middle of it would eliminate any moisture as long as it has a way to vent.


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## rfalk (Feb 26, 2008)

Pook, 
Thanks for noting this. I had heard this before and looked into it. Decades ago there was one mine in the US that had an asbestos problem, so you can find vermiculite that contains asbestos in some old houses, however all vermiculite now mined and sold is asbestos free.


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## milner351 (Feb 26, 2008)

Well, as luck would have it, the closest Menards is over an hour away from me, does anyone know of other chain stores that carry it?

The local HD and Lowe's didn't have it.


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## Metal (Feb 26, 2008)

I have always heard of it being used mixed with concrete then poured in, usually one part Portland Cement to 6 parts vermiculite.  I have never heard of it being used by itself though (there must be a reason).


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## Jay H (Feb 26, 2008)

If you want to find a source, just try to find a local garden/nursury/landscaping store.. As I said, it is quite common for use in adding to potting soil. You can actually buy potting soil premixed with vermiculite but if you just want to buy vermiculite itself, you can generally find bags of it at a garden center type store in your area.

(I've used it for the raising of tarantulas since they do like moisture, I'll add a bit to the soil).

And as a word of caution, it is a fine off-whitish like and can be dusty and I would try not to breathe it in, so I would wear a simple dust mask when dealing with it.  Doesn't matter what the 'experts' say, I'm sure breathing in the dust cannot be good for you.


Jay


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## milner351 (Feb 26, 2008)

Good info on Vermiculite here:

http://en.wikipedia.org/wiki/Vermiculite


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## flueinc (Feb 26, 2008)

yOU CAN GET A INSULATION BLANKET THAT GOES RIGHT AROUND THE SS LINER FROM A GOOD CHIMNEY COMP.


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## rfalk (Feb 26, 2008)

I was aware of the blankets....just looking for a cheaper alternative. bob


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## Harley (Feb 26, 2008)

[quote author="Jay H" date="1204074167"]

(I've used it for the raising of tarantulas since they do like moisture, I'll add a bit to the soil).




*OK - sorry for going off topic here, but I couldn't resist.....

Jay.... Uhm.... can I as what you raise tarantulas for? :vampire:*


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## elmoleaf (Feb 27, 2008)

A few reasons not to use it loose.
1. Small bits tend to leak out around block-off plate and make an ongoing mess.
2. It does absorb lots of water. If you have a chimney without a clay liner/damaged liner, then moisture can migrate through the brick into the flue area. The vermiculite will then absorb the moisture, and when you heat up your metal flue, steam may start burping vermiculite out of the top of your chimney (I've read of this, though don't know if it's true).  Perlite would be a better choice as it absorbs less moisture.

You might consider mixing some Portland cement and perlite to make an insulated plug around your metal flue above the block off plate. Then fill the rest with loose Perlite for insulation. Or, insulate the entire cavity with Portland/perlite mix.


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## dvellone (Feb 27, 2008)

I used to build masonry chimneys, fireplaces, ovens, grills etc.. and used perlite extensively. Same basic properties as vermiculite but performed better and poured much easier. Insulating a flue is quite appropriate. In fact, when constructing a masonry chimney perlite or vermiculite is poured into the space separating the flue tile from the outer masonry units. It is poured dry. Insulating around your liner with either would be a safe and good choice.


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## rfalk (Feb 27, 2008)

Dvellone,
thanks...where would I buy perlite? masonry supply? bob


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## Jay H (Feb 27, 2008)

Harley said:
			
		

> Jay H said:
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> 
> ...


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## denn (Feb 27, 2008)

http://www.perlite.org/
http://www.perlite.org/perlite_info/guides/loose_fill/general/7.pdf
http://www.perlite.org/perlite_info...ulating_concrete/general/perlite_concrete.pdf


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## dvellone (Feb 27, 2008)

rfalk said:
			
		

> Dvellone,
> thanks...where would I buy perlite? masonry supply? bob



a complete masonry supply should certainly carry perlite. I used to purchase it through my local true value - more of a rural setting so they carried a more complete building supply. It should be relatively inexpensive.


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## rfalk (Feb 27, 2008)

Thanks everyone for the input, especially dvellone and LoschCoalStoker. I found a source for perlite here in S. Wisconsin for $8 a bag (4 cf), as opposed to $50-$65 a bag for a vermiculite mix sold by chimney stores online. As dvellone stated, this should work fine for fill in the chimney cavity. I verified this by looking at the Perlite Association website lliterature (see reply above) and reviewing the properties of perlite (much like vermiculite as a fireproof insulation, but is more moisture resistant). It doesn't burn until about 2200 F, so not problem with temperatures of a stove. Will keep you posted on the insert installation (I am doing it myself...I have done one before and didn't burn down the house )...will try to take pics....this is a great forum! Thanks, Bob


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## CodyWayne718 (Aug 16, 2011)

Jus read that perlite expands up to 20 times its original volume when heated to 1600 degrees F. Am I looking at the wrong stuff or can it not expand while in the chimney around the liner? Thanks in advance on the super old thread I dug up!


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## begreen (Aug 16, 2011)

Raw perlite "rock" can expand incredibly when heated rapidly to 1600F. But the stuff you buy has already been expanded and should not expand further. It's like pre-popped popcorn. 

http://www.perlite.net/


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