I know that some folks are talking about getting the insulation right to keep heat inside the oven, and wood consumption down. This is true for both site built and FB precast ovens.

We recommend a 1" Insulfrax insulating blanket (6#) and 4"-6" vermiculite or perlite as a general rule. Here are some simulated insulation numbers we had an engineer do a while back.

James

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I had an insulation engineer run a test, and conclude that the blanket replaces 2" of loose vermiculite. We had them run a simulation where they added 1" of insulfrax, and reduced 1" of vermiculite. 1":4", 2":3", etc. over a 24 hour 1000F exposure. The outer face tested consistently dropped by adding 1" more insulfrax and 1" less vermiculite.

1" Insulfrax Blanket 6#, 4" Vermiculite 1000F** 172F

2" Insulfrax Blanket 6#, 3" Vermiculite 1000F** 161F

3" Insulfrax Blanket 6#, 2" Vermiculite 1000F** 151F

4" Insulfrax Blanket 6#, 1" Vermiculite 1000F** 142F

5" Insulfrax Blanket 6# ******* 1000F** 135F

Thinking about it, I should ask him to add 1# insulfrax, and drop 3" of vermiculite and re-run the test. I would note that after 24 hours of 1000F, (which you will not approach), the outer face is barely warm.

We recommend a 1" Insulfrax insulating blanket (6#) and 4"-6" vermiculite or perlite as a general rule. Here are some simulated insulation numbers we had an engineer do a while back.

James

*******************

I had an insulation engineer run a test, and conclude that the blanket replaces 2" of loose vermiculite. We had them run a simulation where they added 1" of insulfrax, and reduced 1" of vermiculite. 1":4", 2":3", etc. over a 24 hour 1000F exposure. The outer face tested consistently dropped by adding 1" more insulfrax and 1" less vermiculite.

1" Insulfrax Blanket 6#, 4" Vermiculite 1000F** 172F

2" Insulfrax Blanket 6#, 3" Vermiculite 1000F** 161F

3" Insulfrax Blanket 6#, 2" Vermiculite 1000F** 151F

4" Insulfrax Blanket 6#, 1" Vermiculite 1000F** 142F

5" Insulfrax Blanket 6# ******* 1000F** 135F

Thinking about it, I should ask him to add 1# insulfrax, and drop 3" of vermiculite and re-run the test. I would note that after 24 hours of 1000F, (which you will not approach), the outer face is barely warm.

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