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Hearth insulation - Siporex - Forno Bravo Forum: The Wood-Fired Oven Community



I'm Peter Reinhart! Ask Me Anything! Monday, February 15, 2016 7:00-8:00 pm EST

To kick off our AMA feature, we have invited author, chef and master bread maker and host of Pizza Quest, Peter Reinhart, to be our first host! Peter will be in the Forum on Monday, February 15th, from 7:00 - 8:00 pm EST. If you are unable to be online during the live session, you can post your questions in the sticky post. Peter will answer those questions during the live session on February 15th. You can view Peter's answers to your questions as well as what happened during the live session in the session thread.

Ask Me Anything New Forum Feature

You will notice a new forum at the top of the main page called, "Ask Me Anything". This forum will be used for live one hour "Ask Me Anything" (AMA) sessions hosted by people who are knowledgeable in different areas pertaining to wood fired ovens. How it works:
- Each AMA will have a "sticky" thread where the community can post questions they would like answered during the live session. This will allow everyone to participate even if you can't be online for the live session. These questions will not be answered by the host until the live AMA; if you need an answer quickly, you should post it in the appropriate Forum area for the community to respond.
- Another thread will be posted for the live AMA. Registered users who are logged in during the live session can interact with the host by asking questions and receiving responses.
- The live thread will remain in the AMA forum to view after the session.

We hope you enjoy this new feature! Please let us know if there is a topic that you'd like to have as an AMA and we'll look for a host!

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Hearth insulation - Siporex

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  • Hearth insulation - Siporex

    I am soon to start up the insulating layer on the top of the oven stand. I have seen the procedure to use Vermiculite or Perlite and cement (5:1). I have also seen that Forno Bravo advertise insulation plates as an alternative. Forno Bravo is a looong way from being able to supply me with materials, but I am speculating using 100 mm Siporex plates (SIPOREX -> Homepage) instead. It's a type of leightweight (porous) concrete.The U-value is specified (for 100 mm) to: 1.257 W/m2 K (no imperial units here!). Will this do the job?

    Regards from Karl

  • #2
    Re: Hearth insulation - Siporex

    I have done some further investigations around this and the heat conductivity of the Siporex is about 0,114 W/mK while the FB ceramic board is quoted to have 0,111 W/mK (at 600 C). So the heat insulation properties of Siporex should be OK even for approximately the same thickness as a FB plate. May I should add some few centimetres in thickness to be sure. The mechanical strenght of Siporex is also very good.

    My only "concern" in using it is that the sintering (thats when the heat insulation properties start to take permanent damage) is quoted to some 1000 C and the melting temperature to 1100 - 1200 C.

    But will I ever have to worry about such temperatures in my oven? Even at hot-spots and short-term loads?

    regards from Karl


    • #3
      Re: Hearth insulation - Siporex

      This is interesting ....


      It says the fire reaches about 1000f .

      I've seen threads where ovens have hit 1100f to 1200f or 600c

      I've measured my oven in the coals at 700c, but I'm not convinced of the accuracy.

      So I think you will be just fine.

      My thread:
      My costs:
      My pics:


      • #4
        Re: Hearth insulation - Siporex

        Yes, I think the Siporex will stand up to the task. Thank you for sharing your temperature measurements Dave.

        regards from karl


        • #5
          Re: Hearth insulation - Siporex


          For your information I managed to find the ACC blocks recommended as insulation blocks for brick ovens. The recommendation is taken from:
          Maine Wood Heat - Organic Wood Fired Ovens

          You can find it on page 23 in their downloadable instructions. They call the blocks "Ytong (also called foam cement", but it is clear from the instruction that this is ACC (or Siporex as markedet in my country).
          The oven brand is LePanyol which is a recognised company in this trade.

          regards from Karl