Vermicucrete above or below Kaowool

[thebadger]

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.

[dmun]

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.

[Frances]

Originally Posted by thebadger

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.

[Frances]

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

[asudavew]

Originally Posted by Frances

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

[RCLake]

Originally Posted by Frances

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

[Frances]

Aww, thanks guys... I'm touched

[carioca]

Originally Posted by dmun

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

[gjbingham]

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.