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To Thermal Break or not to Thermal Break? That is the question. - Forno Bravo Forum: The Wood-Fired Oven Community

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To Thermal Break or not to Thermal Break? That is the question.

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  • To Thermal Break or not to Thermal Break? That is the question.

    Seems like quite a few of the more recent builds (come'oon class of 2012!), went with thermal breaks between their oven openings and vent arches (throat and oven). I was just wondering what kind of results/benefits you feel you're getting from this mod. How'd you do it (steel tube, gasket rope, air)? Was it worth it? Maybe you didn't bother with thermal breaks, do ya wish you had?

    I think this is something we can all learn from if some finished builder will weigh in. Thanks!

    -Jonathan

  • #2
    Re: To Thermal Break or not to Thermal Break? That is the question.

    It's good practice, expansion and isolating heat being the two primary reasons. Having said that, I notice no perceivable improvement in heat retention comparing my current oven, which has breaks...and all the others I have built that do not.
    Old World Stone & Garden

    Current WFO build - Dry Stone Base & Gothic Vault

    When we build, let us think that we build for ever.
    John Ruskin

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    • #3
      Re: To Thermal Break or not to Thermal Break? That is the question.

      I put one in, an would do it again. Its not a difficult to add one to your build, so why not? What is the downside other than time/material (which is not substantial)?

      As far as heat retention goes, I like to think it retains more heat - but I don't have an identical oven against which to compare it to really know. I do know that there is a big drop off in temp between my inner and entry arches - indicating heat is not transferring from the oven to the entryway. That has to count for something, but there are too many other variables (insulation, door, ambient temp, etc) to really know how much.
      My build progress
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      • #4
        Re: To Thermal Break or not to Thermal Break? That is the question.

        I also have nothing to compare my oven to others but the heat difference between one side of the thermal break and the other is significant enough to convince me that it is a good thing. The difference is quite significant so I would use it if i built another oven.
        Cheers ......... Steve

        Build Thread http://www.fornobravo.com/forum/f3/n...erg-19151.html

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        • #5
          Re: To Thermal Break or not to Thermal Break? That is the question.

          Like Greenman, I put one in (I stuffed gasket rope in the gap), and with my IR thermometer I can measure a big difference between the two sides of the gap. This makes me feel like it is doing something. But honestly my gut tells my that my oven would perform just as well if it wasn't there.

          If there is one "Pro" for NOT having a thermal gap, it would be that it is probably structurally stronger to tie the outer and inner arches together with no gap.

          Comment


          • #6
            Re: To Thermal Break or not to Thermal Break? That is the question.

            Originally posted by boerwarrior View Post

            If there is one "Pro" for NOT having a thermal gap, it would be that it is probably structurally stronger to tie the outer and inner arches together with no gap.
            I'm not trying to be contrary, but tying the vent arch into the oven opening does nothing to enhance or benefit it structurally. If anything, it's better that the vent arch is independent of the dome and oven opening, either with or without a thermal break.
            Last edited by stonecutter; 07-02-2014, 10:37 AM. Reason: Sp
            Old World Stone & Garden

            Current WFO build - Dry Stone Base & Gothic Vault

            When we build, let us think that we build for ever.
            John Ruskin

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            • #7
              Re: To Thermal Break or not to Thermal Break? That is the question.

              What about the floor? If a door is in place the floor is still ventilating out a fair amount of heat. What (hygienic) material could that crevice be filled with?
              Let's keep it metric

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              • #8
                Re: To Thermal Break or not to Thermal Break? That is the question.

                Thin wall stainless steel tubing or channel.
                Attached Files

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                • #9
                  Re: To Thermal Break or not to Thermal Break? That is the question.

                  I went with the stainless steel, but used it as a flashing pan in the vent area. At the back edge, between oven floor and vent floor I am thinking of putting ceramic blanket 1 inch thick and covering it some homebrew mortar with sodium silicate added to make it super hard with repeated fires.
                  Attached Files

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                  • #10
                    Re: To Thermal Break or not to Thermal Break? That is the question.

                    I used stainless square tubing with a soapstone landing. The stainless is only half a brick deep, and sits on some IFB splits. So really it's a combo of stainless/IFB - but the stainless makes a nice and sturdy break between the soapstone and the firebrick - which is sort of fragile.
                    My build progress
                    My WFO Journal on Facebook
                    My dome spreadsheet calculator

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                    • #11
                      Re: To Thermal Break or not to Thermal Break? That is the question.

                      G'day
                      A 36/42in Pompeii is a large mass of brick. Once heated ( and insulated) stays hot for days and more heat than weekend sometimes. I haven't got a heat break and don't think its of real importance to a large oven.
                      However a smaller oven with a smaller mass I wouldn't mind betting even small savings like a heat break would have a bigger effect.
                      Just my 2 cents worth
                      Regards dave
                      Measure twice
                      Cut once
                      Fit in position with largest hammer

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                      • #12
                        Re: To Thermal Break or not to Thermal Break? That is the question.

                        I put in a gap (no metal) all the way around, top, sides and bottom and notice about a 180 t0 200F degree difference. If i were to build another WFO again, which I am, I would probably do the same thing again. No scientific back-up, just my gut feeling.

                        jon
                        jon

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                        • #13
                          Re: To Thermal Break or not to Thermal Break? That is the question.

                          Thank you, this is some great information. It seems like the general consensus is that a thermal break is a worthwhile mod to incorporate into the build. It seems fairly straight forward, just leave a gap of 3/8 inch or so at the reveal where the arch and vent would normally be connected to the oven opening. This can be stuffed with gasket rope along the walls and arch (available readily from Amazon in 6' lengths), and the floor filled with a short length stainless square tube. Benefits are two fold. This will limit heat loss from the oven through the thermal mass of the throat, and reduce stress and cracking in the vent area due to expansion/contraction of the oven. Correct?
                          Thanks again!
                          -Jonathan

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                          • #14
                            Re: To Thermal Break or not to Thermal Break? That is the question.

                            I used rope, so a word of caution. The fibers come off a go airborne, so wear a mask. Then once you stuff the break, coat it with rigidizer or a homemade slurry of Portland/acrylic admix
                            Old World Stone & Garden

                            Current WFO build - Dry Stone Base & Gothic Vault

                            When we build, let us think that we build for ever.
                            John Ruskin

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                            • #15
                              Re: To Thermal Break or not to Thermal Break? That is the question.

                              Would stuffing the gap with a lean mixture of vermicucrete work?

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