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Ellisco1 06-16-2011 04:19 AM

diatomaceous earth under perlcrete
I was rooting around in the insulation photo gallery and saw someone using a thick layer of diatomaceous earth on the top 2/3 of the dome before putting on the mortar/perlite insulation. Anyone have thoughts on what the logic is here?

lwood 06-16-2011 08:37 PM

Re: diatomaceous earth under perlcrete
It turns out the DE is a decent insulator. Here is a table of thermal conductivity of different materials, nice to keep in your toolbox (pardon the pun) next time you need it's conductivity.:) Thermal Conductivity of some common Materials and Gases

Maybe the guy had a swimming pool and had some DE laying around instead of perlite. I wouldn't recommend it, however. It's only half as good an insulator as perlite and that's not expanded perlite.

Ellisco1 06-17-2011 06:19 PM

Re: diatomaceous earth under perlcrete
Thanks for the reply Inwood. I think the swimming pool left overs is a pretty good guess. I got started building a 36" Pompeii after removing a ratty old chimney from a house during a remodel. I'm cutting it all out and dry stacking it now so I'm researching the next step. Thanks again.

Lburou 06-18-2011 03:45 PM

Insulating your oven
The materials you use for your oven will be dictated by what is available in your area. I found a source for vermiculite in Fort Worth you might want to make a note of. You won't need DE.

I bought zonolite/vermiculite masonry fill from Builder's Equipment and Supply, 320 Broadway Ave, Fort Worth, TX -817-332-2373- @ $13.95 per four cu. ft bag. That is a good price. I've read here that this product is coated with silicone to help the particles flow into the voids of concrete blocks after the wall is already built. Hence, there may be an issue with water absorption while making vermicrete. That wasn't a problem for me. The little bit of vermicrete I mixed was fine, I'm planning to pour it into my enclosure and put a top on it to keep it dry.

Insulation is not the place to cut corners. :)

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