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Insulation Question - Forno Bravo Forum: The Wood-Fired Oven Community


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Insulation Question

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  • Insulation Question

    Hi Evryone,

    I have seen where KiwiPete has used 3" of rockwool and 1" of cement & vermiculite to insulate his oven. My question is, how does this compare to 1" of insulfrax and 4" of cement & vermic? I ask this because I only have 4" of space between my brick oven and the inside of the wonderboard exterior wall. The oven is coming along great. Any help would be greatly appreciated!

    Yep. New member today. This site is awsome! Lot's of great info here.

  • #2
    Consider insulation Board as a lining

    If you are strapped for insulation space, consider using insulating board to line the inside of your enclosure. That's what I plan to do. If you see my pix you'll see I planned poorly and left very little room for an enclosure. The insulating board is very efficient and is probly a lot easier than pouring 4" of vermiculite concrete.
    There is nothing quite so satisfying as drinking a cold beer, while tending a hot fire, in an oven that you built yourself, and making the best pizza that your friends have ever had.


    • #3
      Enclosure can also be filled with Perlite

      (M) I poured 7 bags of Perlite over the dome to fill the space between it and the exterior wall enclosure. Each bag held 4 Cu/Ft so That totaled 28 Cu/Ft.

      (M) I dammed the corners with sheet metal so as to conserve the Perlite for the top where the heat is probably greatest.

      (M) Your oven looks like GREAT! I like the orientation and the very thick layer of insulation under your hearth bricks. From the image I got the feeling that your hearth bricks were either deeply embedded or are about 1/2 the thickness of most. ____

      (M) Another oven with the same orientation as yours, and one that turned out beautifully is that of Paulages:

      (M) Click on: http://www.fornobravo.com/forum/show...5&page=6&pp=10

      (M) Paul's thread is arguably the most viewed of any builder's postings. Some of his images that are hosted on PhotoBucket somehow got their links scrambled but there are some images that clearly indicate his 45 degree orientation. Paul is also a fine baker and has contributed about 285 postings to this forum.


      "Everything should be made as simple as possible, ...
      but no simpler!" (Albert Einstein)


      • #4
        I do appreciate the replies, but the question still is "how does KiwiPete's 3" of rockwool & 1" of vermic and the standard 1" insulfrax & 4" of vermic compare in performance?"

        I will post some more pics as I get time.



        • #5

          Great looking oven. Arch into the oven chamber and a second arch (I think) for frame the vent. Nice.

          Insulfrax is a lot more efficient than Rock Wool (Lana di Roccia in Italian). I used it on the Florence oven, along with vermiculite. It was OK, but not great. That was the oven I knew I would only use for a year, so I scrimped by on the insulation. I am continually impressed with Insulfrax -- it's great stuff. It's easy to use, and the price isn't a killer.

          If you are tight on space (which it looks like you might be), I would go for more efficient insulation to get the most bang for the inch.

          Still, all were are trying to do is make your oven "better". You can insulate with 3"-4" of vermiculite, and it will still cook just fine. We're in the good, better, best zone.
          Pizza Ovens
          Outdoor Fireplaces


          • #6

            Thanks for the reply. That's what I needed to know. Looks like I'm getting some insulfrax as nothing but the best will do.

            Here's some more pics if you guys are interested.


            • #7
              I like the way you filled your gaps.

              The inside of your dome is beautiful. You took the time to fill in the gaps from the inside, which I wish I had done. It looks spectacular.
              There is nothing quite so satisfying as drinking a cold beer, while tending a hot fire, in an oven that you built yourself, and making the best pizza that your friends have ever had.


              • #8

                I tried the stirofoam mold but couldn't work with all that foam in the way. So after spending all that time cutting the foam, I pulled it all out after the first brick and did all of them by hand and finnished each joint with a sponge as I went along. I am pleased whith it too. Thanks for the compliment.


                • #9
                  Can you come back and re-fill the gaps inside your oven? Do you want to?

                  It would be great to hear from other builders if they think that is helpful and/or difficult. You would have to use a high quality, true refractory mortar -- not portland-based fireclay mortar, as it would be exposed to direct heat.

                  Worth it?
                  Pizza Ovens
                  Outdoor Fireplaces


                  • #10

                    James, Fio,

                    I'd say filling gaps is worth it, although you have to be a bit of a contortionist to do it. Just mix up a "fairly" dry batch of refractory mortar at about the same consistency as for pointing, wiggle in on your back and do it. That way, the edges of the bricks wont be exposed to driect flame.

                    "Made are tools, and born are hands"--William Blake, 1757-1827