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Rockwool for insulation - Forno Bravo Forum: The Wood-Fired Oven Community

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Rockwool for insulation

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  • Rockwool for insulation

    Hi,

    I find it very difficult to get access to some of the materials recommended for insulation of the oven (ceramic fibres etc.). I did come across a 100L bag of perlite. But now I am a bit worried that this material could drizzle into the small cracks which necessarily must form.
    Why could I not just use rockwool for insulation? It is claimed to withstand more than 1000 C and after some discussions on this forum I am convinced that I will never reach more than between 600 - 800 C in my oven. Any comments or advice on this thought?

    regards from Karl

  • #2
    Re: Rockwool for insulation

    I did a wiki search on rock wool and found the name represents a wide varity of products.

    One item I did note:

    "All European produced rock (stone)wool and glass wool is bio soluble". This would imply that it might be affected by water" - so becareful.

    Also - be careful cause you can't trust everything you hear on the internet.

    Christo
    My oven progress -
    http://www.fornobravo.com/forum/f8/c...cina-1227.html
    sigpic

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    • #3
      Re: Rockwool for insulation

      Rockwool is oftem stocked by the same suppliers as ceramic fibre blankets, here in Australia anyway.

      Have you tried talking to industrial insulation specialists. Often I've found going to the high-end of users to find what they use and where they get it from and work back to the supplier can be effective.

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      • #4
        Re: Rockwool for insulation

        "Bio-soluble" in this context means that the fibers will dissolve in your lungs, so they are a lesser silicosis hazard. Wear the respirator anyway.
        My geodesic oven project: part 1, part 2

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        • #5
          Re: Rockwool for insulation

          For my first oven I used fibreglass insulating bats (which I think is also refered to as rockwool) It did the job ok and on inspecting it when I removed a floor firebrick, the fiberglass bat under the brick appeared not to have deteriorated in any way. Trouble I found withe the fiberglass on the outside of the dome was that it compressed very easily and it then made the job of chickenwire over it very difficult. I now prefer vermiculite/cement 10:1 which goes firm when set.
          Kindled with zeal and fired with passion.

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          • #6
            Re: Rockwool for insulation

            Hi Karl
            Purolite is mixed 5 to one with concrete. I am using it and have never heard of any spilling through the cracks. I believe that this a standard tried and true application and you won't have problems. Incidentally my son will be in Bergen Noway on the 20th...a good-guy collage kid,
            sigpic

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            • #7
              Re: Rockwool for insulation

              Good day!

              If you are going with an enclosure vs igloo, you can use it loose as well and the joints in your enclosure must be pretty close to keep from spilling out. (Please don't ask me how I know!)

              Christo
              Attached Files
              My oven progress -
              http://www.fornobravo.com/forum/f8/c...cina-1227.html
              sigpic

              Comment


              • #8
                Re: Rockwool for insulation

                Thanks everybody for replying,

                I am planning to do an enclosure rather than the igloo. Even though the igloo principle may sound very adabtable to our climate ! The rain and the snow ower here call for a proper enclosure and I was worried about using loose perlite (penetrating into cracks,- and now seeing Christo's experience ...). I agree that using it with cement should be better. But I thought that the job of mixing and "smearing (?)" it all over the oven could all be avoided by just using rockwool (I do not know the US brand name but it sound very much like the type David s was using. It is sold both as hard mats and in softer and thicker sheets).
                I haven't heard anything in your comments that actually should be a "show-stopper" in that respect?!

                regards from Karl

                PS Laborer,-hope your son have a good time in Bergen. Just heard that Metallica had a concert there yesterday. He missed them with a couple of days. DS.

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                • #9
                  Re: Rockwool for insulation

                  Karl,

                  I used Rockwool ( stonewool ) 4" thick slabs when I built my powdercoat oven and I can run it up to 1000f and the metal oven is cool to the touch on the outside. I cut it to fit with an electric meat carving knife.
                  Attached Files

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                  • #10
                    Re: Rockwool for insulation

                    One of the problems with insulation technology is that there is no standard vocabulary. What might be "fiberglass" in one place, might be "mineral wool" in another. After all, silica is a mineral. This doesn't mean that every type of insulation is suitable to every application. One of our members had a cracking problem when his insulation board turned out to lack water resistance, and squished when it got damp.

                    If you are using untested materials, you need to read material data sheets, and talk to applications engineers with the manufacturers. If those things are as difficult for you as they are for me, you need to follow the tried and true standard practice.

                    That said, we like to hear about experiments, and what different materials are used in different countries.
                    My geodesic oven project: part 1, part 2

                    Comment


                    • #11
                      Re: Rockwool for insulation

                      Hi Karl,

                      I missed this discussion, or I would have chimed in sooner... I used rockwool on my oven and it seems to be working fine.

                      Having said that, I was told that rockwool comes in various qualities. The regular house insulation stuff may well withstand 1000 C but only for a once off house-burning-down situation and not the weekly lets-see-how-hot-we-can-get-this-thing effort we are interested in. The stuff I used was developed for insulation round furnaces and indoor ovens.

                      And its a hassel keeping it dry while you finish the oven. But appart from that its fine.
                      "Building a Brick oven is the most fun anyone can have by themselves." (Terry Pratchett... slightly amended)

                      http://www.fornobravo.com/forum/f8/p...pics-2610.html
                      http://www.fornobravo.com/forum/f9/p...nues-2991.html

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                      • #12
                        Re: Rockwool for insulation

                        Rockwool / stonewool slabs are pretty standard insulation also called by the name " fire block " in the construction world. 24" x 48" x 1,2,or 4" thick.
                        I got mine in Dallas at a hvac supply house and it is prety amazing stuff. Same material used in hydroponics as a growing medium. I also used some to protect parts when I tig and gas weld.

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                        • #13
                          Re: Rockwool for insulation

                          Mineral wool is made from molten glass, stone or slag that is spun into a fiber-like structure. Inorganic rock or slag are the main components (typically 98%) of stone wool. The remaining 2% organic content is generally a thermosetting resin binder (an adhesive) and a little oil.
                          The relation between temperature and thermal conductivity is indicated in the diagram below:
                          Attached Files

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                          • #14
                            Re: Rockwool for insulation

                            Hello everybody,

                            Thanks for all replies. I have concluded that the mineral wool (from stone) which I plan to use is suitable. At the present i am fitting the flue pipe to the chimney and building the enclosure.

                            regards from karl

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