vermiculite v's insulation blanket

[markbotts]

Bit of a tech question this one - I'm building a pompeii oven and I'm limited on space - I've built the dome and put one layer of 1" blanket on. That leaves me with enough space for a 3" vermiculite layer + render. I've got enough blanket to do another layer so my question is - which is better 2"blanket/2" vermiculite or 1"blanket/3" vermiculite?

[ringo]

Mark

Welcome to the forum, good place to ask questions like this - I have!

Can't answer your question specifically as I'm taking the shortcut of a modular oven but have still got to cover it.
One tip I did get from Liam at Kilnlings (top bloke recommend him) is that before any cement type render goes on, you wrap tin foil (I.e.layer of ceramic, then tin foil,l then chicken wire) this way, any rendering moisture wont be absorbed into the blanket.
As was pointed out when I made this comment in my thread though is that the oven has to be fully cured first though else the internal steam won't escape the foil

Hope this helps, oh and post some pics, you'll be asked for them!
Good luck

[markbotts]

Cheers for that Ringo - good tip!

[faz]

Generally the blanket should have better insulating properties than vermicrete, so 2" of blanket plus 2" of vermicrete will give you better insulation. BUT (!) I am not sure how easy it will be to do 2" of vermicrete as it is a bit of a pain to work with! Others may be able to tell you how easy it will be.

[bookemdanno]

Do not use the foil unless you thoroughly dry out and season your oven first.
Otherwise the moisture within the brickwork cannot get away and will condense on the inside of the foil.
I wholeheartedly disagree with the use of foil, and do not believe that the amount of water within the render will affect the blanket enough to warrant using it. Sorry!

The blanket is a better insulator than the vermicrete. The Vermi is a layer that acts as support to the render, and not likely to crush the blanket too much. As its an insulator, its just an extra plus.