Air as insulation

[Sherby88]

HeIlo, I want to build a pizza oven at home, and I'm trying too too cut the cost since I will use it 1 3 per month.
I know from house construction that a layer of air is one of the best insulation. I am wondering if I would built a layer of about 2-3" of air beneth the brick floor would be good instead of vermiculite concrete.
The bricks would be layed on a metal plate and that on some supports to make the layer.
Has anyone tried or researched this?

[jeeppiper]

Re: Air as insulation

Ive been wondering that same thing....I have seen some folks create an insulating slab by using a layer wine bottles laid into concrete. The wine bottles would give you nice structural integrity to the slab to support the weight of the firebrick....

[Tscarborough]

Re: Air as insulation

Small layers of air will heat rapidly and large ones will begin to convect. The best way to use air as insulation is to encapsulate it into ass many small pockets as possible. Perlite is cheap, cheaper than the metal you talked about would be by a factor of two or three times.

[david s]

Re: Air as insulation

steel is also a much better conductor of heat than the floor bricks so it will draw heat away from them, simply heating your insulation space. It is also prone to corrosion from heat/moisture.

[Sherby88]

Re: Air as insulation

Thank you for the replies
This was a cheap solution because I would have used only very thin a metal sheet with supports. But in has some flaws as mentioned, like corrosion and heat conductivity.
Or could I use rigid mineral wool blanket?
There are talks about using this instead of refractory insulation, but it burns the organic parts from it and releases a smell. But the smell would be only the first and maybe the second time I would fire up the oven not all the time I think.
If no then it looks like I have no choice but to use perlite/vermiculite concrete.
Here in my country alot if not all wood ovens are done using a layer of broken glass, but I don't think this is good enough.

[Bookemdanno]

Re: Air as insulation

Don't use standard Rockwool, it'll just turn to dust in no time!
Not much good, when your whole oven is supported on it!

Thermolite, or expanded cement blocks of any type will do well.
Leca?

[brinkler]

Re: Air as insulation

Leca? I've actually been wondering the same thing, wouldn't something like the H+H aircrete block be good for the base of the oven? Being that the foam glass can be pretty hard to come by in some areas (Denmark for one)

Celcon

It also has some other nice qualities for the oven construction:
Specs.pdf

Strong - you can build your oven 4 storeys tall
Airtightness - Underwater oven anyone?
Sound insulation - Quiet down that ROARING fire
Fireproof - Well... Duh!
Durable - Water resistant, frost resistant
Excellent ballistic impact performance - probably most useful in Texas
Build quality - Made to tight tolerances... Yea precision oven it is!

From my personal experience I found it to be easy to work with, you can shape it with a normal saw and sand it level if you need to.

With an isolation factor of : 0.15 W/mK it seems to me that it should serve well?

Isolation values keep being a mystery to me but I've found these:
Concrete: 1.40
Vermiculite: 0.65
Rockwool loose: 0.11
Source: W/mK values

Any thoughts on this?