Vermicucrete above or below Kaowool

[jcg31]

Having learned the miracle of insulation these last two weekends with the curing fires, I have decided to add a layer of vermicucrete to the outside of the dome. I see in posts that some add it directly to the dome, while others are laying down the ceramic blanket first and then putting down the vermicucrete over the blanket. Does anyone know the relative benefits of either approach. Does applying directly to the dome provide more structural support?

Thanks for any thoughts.

Jim

[dmun]

I put the blanket outside the brick dome, and covered it with vermiculite concrete. The perlcrete has no structural strength, so I don't think it will help with anything structural, except maybe supporting the stucco on the outside of the dome. Besides, the blanket is the much better insulator, and you want it where it will do the most good.

[NanyukiTom]

Hi JCG31,

I live in Kenya and have been unable to find any sort of insulating blanket to put around the dome. I finally opted for 6 inches of vermicucrete. It seems to be working fairly well. I was a bit concerned about expansion and the need for a woven insulation blanket but the vermicucrete seems to be working just fine.

I agree that it adds no structural elements to the whole program. It's acutally a bit of mess to work with. I ended up "sculpting" a layer of chicken wire (1/2" opening) about 6 inches above the dome outer face and then filling the space between the dome and the chicken wire with the vermicucrete. I don't see how it ever would have stuck without the chicken wire to hold it in place.

Tom T

[gjbingham]

I think dmun has it correct. Blanket first, then vermicrete.

[CanuckJim]

JCG,

Have to add my assent to what Dmun and George have said. All the FB installations I've done are assembled with the blanket(s) first, then chicken wire, then wet insulation coating, whether vermic/cement or something else.

You won't get any structural advantage by using the wet coat first, and the blanket(s) is/are the better insulator to have directly against the dome.

Jim

[jcg31]

Blanket first, then vermicucrete. Done! Thanks all.
Jim

[RCLake]

Jim, I know you are installing 50sf of 2" blanket which probably means you will have 3" coverage over your dome. If you are planning on adding vermiculite over it is it because More Is Better or have you noticed what you have so far is lacking?
As you know I have 50sf of 3"(4-5" of coverage) that I'm hoping will be enough, but I don't know.

[jcg31]

No, I am just buying the "you can never have enough insulation" thinking. But I had the top outer surface of the dome to 725 degrees this weekend (inside top was 850-derees). The wool on top of the dome was merely warm, I am certain if I had two layers in place the wool would have been entirly cool to the touch. You should be fine with what you have.

Jim

[RCLake]

Jim, thanks for the info.

If you are at 850 in the dome and day 5 goal is 700 have you started cooking yet?

[mfiore]

Perhaps a silly question from one who hasn't started building yet, but if the blanket is a superior insulator, why skip the vermiculite and put down more blanket? Does the vermiculite serve some other purpose?