I plan to have a closed top like the attached photo. After insulation blanket, can I fill the void of space with a sand and vermiculite dry powder mix before sealing the top? Any advise is appreciated.
Anybody got any ideas?
I would recommend reading from the wood fired oven by Richard moscovich(sic). He has a chapter devoted to understanding how ovens work. In that same chapter he discusses insulating materials.
Also, maybe in this book, I read a story about someone compressed the insulation and it lost effectiveness. Basically, a guy put his exhaust through some wooden rafters to the roof. To avoid a fire he packed in a ton of fiber blanket. Until he smelled burning and realized, without the air trapped in the blanket, it was far less effective.
The vermiculite does not sound like a terrible idea because it’s so light. It could create some problems if the weight gets up there.
That does make a good-looking design.
I would recommend that you still do the wire lathe (chicken wire) and stucco shell. The idea is to protect your mineral fiber insulation, no matter what else you build over it. While the vermiculite mix is an interesting idea, and it might take a little weight out of your fill mixture, I don’t think it adds anything in particular to a sand-based fill.
However, if you instead filled the space with Vermiculite OR Perlite, that would fill the space and add practically no weight at all. Another benefit would be that the granules are bigger than sand, so no chance of seepage through cracks.
Since much of the area is taken up with the oven itself, my very rough guesstimate is that 4 to 6 cu.ft. of the material would be enough.
Looking forward to seeing what you come up with!