Vermicucrete above or below Kaowool

[gjbingham]

Re: Vermicucrete above or below Kaowool

Sometimes its just a matter of finding a better supplier for the vermiculite. I paid $35 a bag for the first three, then after exensive searching found a place that sold it for $17.

[carioca]

Re: Vermicucrete above or below Kaowool

The vermiculite concrete is about a quarter the price of high-tech insulating materials. It also fits into cracks and voids, and forms a smooth surface, which the overlapped blanket does not.

dmun, in my nick of the woods vermiculite is almost $38 per 3cu ft bag - you'd probably need at least two bags of this stuff, plus the cement. So at around $80 it's only marginally cheaper here than the carton of Kaowool blanket, which I bought for under $100...

In fact that was the second of two cartons I bought - one was $120! - so I could put TWO layers of blanket around my 39in dia. dome, plus some extra over the top.

For good measure, I also placed chickenwire supporting two thick layers of vermiculite concrete squeegeed over the blanket... When this layer dried out, it made a handy shell for the twin coats of cement render (stucco to you, I believe).

With all that insulation, the outside IR temp measured 50 degrees centigrade (amid 27C ambient temperature) this afternoon on top of the dome when the inside temperature of the dome top measured 384C (about 729 F)!

So I'd say: if you can afford the extra few quid, by all means put on 2in (50mm) of fibre insulation, then perhaps as much again in vermiculite concrete, for a cool oven (on the outside, that is: I managed to burn a load of rolls badly today because I didn't wait for the damn dome to cool down a bit :-)

Cheers,

LMH

[Frances]

Re: Vermicucrete above or below Kaowool

Aww, thanks guys... I'm touched

[RCLake]

Re: Vermicucrete above or below Kaowool

Hey, I just noticed, I'm master builder now!!! Wow, when did THAT happen??!

It's going to cost James a bunch to ship that flour to you. Keep up the great cooking. I need inspiration

[asudavew]

Re: Vermicucrete above or below Kaowool

Hey, I just noticed, I'm master builder now!!! Wow, when did THAT happen??!

About 9 posts ago! give or take...

Congrats Frances, but I already knew you were a master builder.

(and Chef, I might add)

dave

[Frances]

Re: Vermicucrete above or below Kaowool

Hey, I just noticed, I'm master builder now!!! Wow, when did THAT happen??!

[Frances]

Re: Vermicucrete above or below Kaowool

Don't ask where I keep my copy.

...bedside table, right?

Using the digital version as a screen saver at work would be pretty good, too.

[dmun]

Re: Vermicucrete above or below Kaowool

The vermiculite concrete is about a quarter the price of high-tech insulating materials. It also fits into cracks and voids, and forms a smooth surface, which the overlapped blanket does not.

[thebadger]

Re: Vermicucrete above or below Kaowool

Mfiore,

You have a lot of options:

All Blanket,
All vermiculite or an equivalent
A mixture of both - the route I'm going to use.

I think it really boils down to cost but my understanding is the blanket is superior (the plans detail which ratio to use of each). James cells a new less expensive FB blanked that I just purchased.

I'm actually planning on using 2 inches of blanket then vermiculite to fill the void. I'll prob end up using way more vermiculite but I would rather have too much.

Thanks
Dick

Hey, I haven't built yet but I feel comfortable answering some questions given I've read the plans so many times. Don't ask where I keep my copy.

[mfiore]

Re: Vermicucrete above or below Kaowool

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?

[RCLake]

Re: Vermicucrete above or below Kaowool

Jim, thanks for the info.

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

[jcg31]

Re: Vermicucrete above or below Kaowool

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]

Re: Vermicucrete above or below Kaowool

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]

Re: Vermicucrete above or below Kaowool

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

[CanuckJim]

Re: Vermicucrete above or below Kaowool

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