Mix Your Own Pour-In Liner Insulation Mix

[Mr A]

Has anyone found a vermiculite to mortar ratio to mix up your own insulation mix? Both vermiculite and potland cement are cheap, so 2 bucks a pound for a bag of Evergard seems excessive. Is there something else in it besides these two cheap ingredients? I have a few sites mentioning 6:1, or 5:1. Any thoughts? Thank you

 

[pgmr]

Is there a reason you want to go with a concrete type insulation vs a loose fill (poured in perlite or vermiculite)? If your chimney has a clay liner in good condition the loose fill will be much easier to install (and remove later, if needed). If the clay liner is in bad shape or non-existent, you'll need to go with an insulating wrap for safety.

 

[Mr A]

No reason other than I didn't know about loose fill. I was thinking the pour in would be easier for getting the liner through, and would also take care of sealing the bottom of the flue to prevent loss of heat. And also, I'm think a heavier, liquid cementitiost mix will sort of flow into all the nooks and crannies making a tight seal.

 

[Black Jaque Janaviac]

Info on loose fill:

Place liner FIRST.

Purchase vermiculite or perlite from garden supply store in 4 cu. ft. bags.

Haul bags up to rooftop.

Pour content of bag in space between liner and old chimney. Lift liner a tad to settle any bridging and top off as needed.

Place liner top plate and clamp tight, seal with RTV silicon to minimize air leakage through insulation.

 

[pgmr]

You'll need to have a good seal between the bottom plate and the ss liner. If you don't, the insulation will work it's way through the gap. Stove door gasket works pretty well.

 

[jimbom]

Perhaps you could use your flue liner as the form. I mean by that to cast it in place in the chimney.

Simple home tests will tell you what you want to use. The following would take a couple of evenings, but nothing could be more fun.

Perlite is recommended over vermiculite because of moisture absorption properties. Wear a dust mask and eye goggles as you are dealing with very small very angular particles that will damage your lungs. The perlite will have segregated in the bag as the fines and dust move around in response to transportation. Dump the entire bag on a plastic sheet or smooth surface and turn or blend the contents until they are mixed. Spread the pile into a flat circle and make pie shaped pieces with the edge of a flat shovel or similiar. Use the amount of each piece that you need for your sample and leave the rest.

Buy a bag of cement and a bag of construction perlite and run some simple tests. Make little forms from tin cans or other suitable thin metal. At one sitting do all of the test samples some place where it will not freeze and the samples will not be disturbed. Mix three batches of 6:1 by volume with slightly varying amounts of water(Goldylocks protocol). Record the weight of water for each batch. Do again for 5:1 and perhaps 7:1 or 4:1. You may want to pack the mixes with a metal rod to make sure each fills the form completely. Use the same number of strokes on each sample. Cover each sample with saran wrap for two weeks or more. Don't want any moisture to get out. Don't touch or handle the samples when finished.

Record the fresh sample characteristics that you noticed while mixing and placing the samples. Perhaps workability, flowability, stickyness and ease of mixing. After the two weeks or more curing, check the hydrated samples for characteristics that you want. Perhaps, weight, strength, no voids, blow torch test IR temperature(face mask required as these may explode), water absorption-drain-freeze, etc. When you are done, you will know your material with regard to strength, response to heat, and performance in freeze thaw situations. Bonus. You can bore people to death at parties with this tale.

If you do line your flue, clamp little metal tabs on the outside of the liner to center it in the chimney. Do the job a few months before freezing weather to let it dry. Have a few small autumn fires to insure any moisture is driven out.

The flue liner will withstand brushing over the years. When the liner fails, the strength of the perlite/concrete will continue the ability to be brushed. This and perhaps better response in an earthquake is the advantage of hard perlite/concrete compared to loose fill. Loose perlite fill must be installed such that the bottom of the chimney is absolutely sealed tight. The fine dry dust will find any crack that opens from thermal movement over the years. But careful workmanship will solve this. And finally, be assured I have not been drinking before writing. At least not right before.

 

[Mr A]

Well, thanks jimbom. That is the idea, to get insulating material around the liner. I found this mix table for insulating concrete mix. I dont think making test batches would be practical. From what I gather, a construction grade perlite is needed, not the horticultural grade sold at plant nurseries.
(broken link removed to http://www.perlite.org/perlite_info/guides/lightweight_insulating_concrete/general/perlite_concrete.pdf)
A sack of cement is just a few bucks. I have not yet located where to get correct grade perlite,. Maybe that is why the insulation mixes are so expensive?
I've been googling all day, this stuff is hard to find! Mostly because it is not sold as perlite, but as a tradename of the companies that process it. These bags don't look familiar, but I'll take a look next time I'mat the home supply store to see if they have any before ordering online.
http://www.hometownperlite.com/LCPM_details.html

Please correct me if I'm wrong, but this looks like the ticket-Cheap, easy, quick.

 

[WoodpileOCD]

You can order it online from Home Depot.

(broken link removed to http://www.homedepot.com/webapp/catalog/servlet/Search?keyword=thermorock&selectedCatgry=SEARCH+ALL&langId=-1&storeId=10051&catalogId=10053&Ns=None&Ntpr=1&Ntpc=1)

 

[Mr A]

Wrong stuff woodpile, that's soil amendment.

 

[branchburner]

Check masonry supply stores for cheap bags of perlite.

Bear in mind that a homemade insulation may not be in strict accordance with the liner manufacturer's approved insulation applications, voiding the warranty (and potentially violating code, if code requires you follow all manufacturer instructions to the letter).

If you do loose perlite, having at least a small portion of it mixed with cement at the base of the liner will help keep the loose perlite from sifting down from above.

 

[jimbom]

.....
http://www.hometownperlite.com/LCPM_details.html

Please correct me if I'm wrong, but this looks like the ticket-Cheap, easy, quick.

That is the stuff. Let us know how you come out. Good luck and good wood burning.

 

[Mr A]

Warranty says I have to pay a certified chimney professional to install it and maintain it annually. Warranty is useless. That expense will buy a lot of new liners! I don't know if I even need to insulate. I have a 32 yr old terra cotta lined chimney in good shape, it's back side is in insulated, unheated garage area. I don't know about my construction, but practice has been to insulate with perlite between the terra cotta and masonry bricks.