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Dome insulation - Forno Bravo Forum: The Wood-Fired Oven Community

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Dome insulation

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  • Dome insulation

    I'm building a small dome (36") and my dome consists of :
    Firebrick, covered by 1" of Heat Stop II, followed by a mix of Portland cement with fireclay for 1 1/2", followed by a 2 1/2" layer of Vermiculite/Portland Cement.

    Do I have enough insulation??

    If I do have enough insulation, how soon after laying the vermiculite/cement mix can I lay the stucco over it?

    Thanks, Jim

  • #2
    Re: Dome insulation

    2 1/2" layer of Vermiculite/Portland Cement.
    Do I have enough insulation?
    No, Four inches of vermiculite concrete is the recommended minimum. Do you have that much under your floor, as well?
    My geodesic oven project: part 1, part 2

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    • #3
      Re: Dome insulation

      I have 4" of FoamGlas with 2" of vermiculite/cement mix underneath

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      • #4
        Re: Dome insulation

        I am wondering about the added thermal mass (1" Heatstop & 1 1/2" of portland/fireclay). If you are following the plans and using 1/2 bricks - 4 1/2" is more than enough mass.
        You would be much better served eliminating the added mass and adding 2-3 more inches of insulation.

        RT

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        • #5
          Re: Dome insulation

          I have 4" of Foamglas underneath with a 2" layer of verm/cement base on top. Thanks

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          • #6
            Re: Dome insulation

            jmonag,
            You should cure the oven before doing the stucco.
            Kindled with zeal and fired with passion.

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            • #7
              Re: Dome insulation

              I dont think you can ever have too much insulation, I have 2 layers of 8# water soluble kaowool over the bricks, then about 4-6 inches of vermicrete,, as well as 4 inches of vermicrete under the floor... when I am done cooking for the night, If I leave the oven door on I still have a floor temp over 300 degrees in the morning.

              Mark

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              • #8
                Re: Dome insulation

                Thanks for the advice from all those that replied. Just a few more questions on the insulation. I do plan on expanding the vermiculite/cement mix, but would I cover that with a portland cement/fireclay mix before the stucco or can I just go with stucco??
                Also, on the curing portion, should I wait a week then start the fires then cover with stucco or should I wait a week, cover with stucco wait another week and then start the fires??

                Again, thanks for the replies. Jim

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                • #9
                  Re: Dome insulation

                  You can put the stucco directly over the vermicrete. Give the vermicrete at least a week to set (more would be better because it contains so much water) then do the curing fires to eliminate the rest of the water. You can feel the dampness with your hand. Then do the stucco and wrap it up for a week to keep the moisture in the outer layer, making it stronger. Then unwrap it and fire away. Moisture trapped in the vermiculite layer can lead to cracking of the outer shell.
                  Kindled with zeal and fired with passion.

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                  • #10
                    Re: Dome insulation

                    Thanks for the advice. Jim

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