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  • #16
    Re: Insulation Efficiency

    RE: How much slab (cooking floor) insulation:

    I have ONLY the 2" of FB Board sitting directly on my 4" concrete slab that I poured onto Durock cement board (I did not use plywood, placed the cement board and just left it there after the 4" conc. pour) and last night I had 800 and 900 deg pizza fires for 4-5 hours. The infrared thermometer said the cement board under my oven was 80 deg and hit 91 deg at the hottest period. This morning I still have 500 degrees in the oven and 80 deg on the cement slab underneath. I think that is very low heat loss.

    Use these numbers for comparissons on the efficiency of FB board 2" vs (or in addition to) vermiculite - concrete insulation under the oven.
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    • #17
      Re: Insulation Efficiency

      Is it possible to over insulate ?
      If you use more insulation than is needed to keep the outside of your enclosure at room temperature, you're wasting money, but there is no particular harm. You can't go wrong with the recommendations in the plan.
      But fiberglas is sure a great value compared to alternatives.
      Be sure to keep domestic fiberglass insulation away from anything hotter than you can touch: It has an organic binder that breaks down (and smells bad) when hot.
      My geodesic oven project: part 1, part 2

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      • #18
        Re: Insulation Efficiency

        Has anybody use rockwool? I'm insulating at the same time as I'm building the dome, packing loose rockwool in a 1" space I leave in the wet vermiculite mix next to the dome. The final shape is unimportant as the whole thing will be enclosed. If you're wondering why I'm using rockwool, I have a large bag of it left over from a different job and it seems a shame not to use it.
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        • #19
          Re: Insulation Efficiency

          "Rockwool" is a term we don't use in the US. If it's domestic insulation, like fiberglass, it may have organic binders that will burn and stink at the right-next-to-the-dome temperatures. Before you get too far, heat up your kitchen oven to 550 degrees f. (288 degrees c.) put a chunk of the rockwool in, and see if it stinks up the place.

          If it's a refractory insulation, you should be good to go.
          My geodesic oven project: part 1, part 2

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          • #20
            Re: Insulation Efficiency

            Two questions....

            Can you just pour vermiculite and fill in around the dome without an insulating blanket?

            Hardware stores sell insulating blankets to wrap around hot water heaters, heat pipes, etc. Can you use that material?

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            • #21
              Re: Insulation Efficiency

              Are you talking about the insulation over the dome?

              Could you use the blanket as part of the insulated hearth?

              So are you saying that the insulfrax blanket is more efficient than the vermiculite?

              We poured the insulated hearth this evening - I used 3.5 huge bags of vermiculite and almost 2 bags of portland cement. It wasn't enough to fill the form, so I made angles at each corner, just using bricks (regular bricks), to take up space. I wanted about 5.5 - 6 inches of depth, but I think I got about 4.5 -5 inches of depth. I would have made more, but I ran out of vermiculite and the store was closed. But if I were to get some more tomorrow, could I pour on top of what is already laid?

              As far as extra thermal mass - we decided just to add more fire if need be....is that ok?

              Cecelia

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              • #22
                Re: Insulation Efficiency

                yes, I was talking about the dome, not the insulated hearth. Can we just pour vermiculite over the dome without the blanket or do we still lose too much heat?

                As far as adding more vermiculite tomorrow, that should not be a problem if you are just pouring more over the dome....

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                • #23
                  Re: Insulation Efficiency

                  I was actually talking about the insulated hearth - Can I add to it even a day (or more?) after it's poured?

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                  • #24
                    Re: Insulation Efficiency

                    There should not be any problems adding more vermicrete to the insulating slab. Adhesion should not be a problem - the stuff is pretty rough and porous, so it will bond just fine with the previous layer. It is also under compression when completed, so nothing will be moving around.

                    RT

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                    • #25
                      Re: Insulation Efficiency

                      I want to go back to Cecelia's question about whether you can use the Insulfrax blanket in the hearth. I would say no. You want something that will be structural like FB Board or vermicrete. The blanket has no compressive strength.
                      And to answer the question about efficiency, the blanket is more efficient than vermiculite. If you were to cover your dome in vermiculite, you'd need 5 inches compared to 3 inches of blanket to get roughly the same performance. I believe that's the consensus here. There's nothing wrong with using vermiculite to insulate the dome. You just need a thicker layer.

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                      • #26
                        Re: Insulation Efficiency

                        just thought I would add my 2 cents. My dome is Alfa Caminetti which is a lightweight refrax material construction. I set the hearth on two courses of firebrick with refractory cement then covered the dome with 2" of refrax and vermiculite blend.(looked like a huge oatmeal ball.) Then the entire dome was covered with loosely packed 20 cu. ft of vermiculite between the brick enclosure. The efficiency is incredible. I have had 1000 plus temps that 24 hours later are still sustaining temps of 2-250 degrees. I have been burning seasoned almond which is a nice hot wood and good coals.

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                        • #27
                          Re: Insulation Efficiency

                          The e-book says 2-3 inches of Insulfrax Blnket is enough insulation. I have enough 8#, 1" Kaowool to cover my oven with 2 inches. Is this enough or should I buy another roll? I am planning an igloo design and want to stucco right over the Kaowool.

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                          • #28
                            Re: Insulation Efficiency

                            I am planning an igloo design and want to stucco right over the Kaowool.
                            The question of is it enough is just a matter of how much heat you want your oven to retain.. I used the 8# kaowool too 2-3 inches, then about 4-5 inches vermicrete, then stucco..

                            I can cook all night and still have 400-500 degrees in the morning if i leave the door on,,
                            Im sure you would be fine with that plan for pizza's but baking may be a problem..

                            Just my opinion,, Mark (not an expert)

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                            • #29
                              Re: Insulation Efficiency

                              That's about what I get, too.

                              2 to 4 inches of ceramic insulation with 4 to more inches of loose vermiculite and 2 inches of FB board underneath.

                              Christo
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                              • #30
                                Re: Insulation Efficiency

                                I thought that I read FB is now recomending Ceramic blanket only insulation. Has anyone else read this? If so, how much is required. The Ebook says 2 to 3 inches is enough.

                                Phil

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