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Alternative Insulation

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  • Alternative Insulation

    Hello cooks and cobblers!

    I am attempting to build a wood fire oven in Uganda (part 2?). I live in Kampala, the capital city, and building materials are a bit easier to find than the other East African threads I've seen here. However I'm having trouble finding vermiculite or perlite. Ironically Uganda has a mine which produces vermiculite for export (an australian company) however I've been in touch with them and they have informed me the mine has ceased production and they can't provide it to me.

    I've seen other suggestions here like woven ceramic but so far I haven't had luck in finding that in Kampala either.

    I'd appreciate suggestions of more commonly available materials that could function as decent insulating material.

    Thanks!

  • #2
    Re: Alternative Insulation

    People have traditionally used straw, sand, clay and sawdust for insulating kilns.
    There was talk of using lava stone "scoria" in the cement mix hear too.
    If you enclose your dome you can use glass bottles on top or anything that wont melt but traps air.

    Comment


    • #3
      Re: Alternative Insulation

      Scoria, or pumice if you can get it. Lots of air holes in those little rocks, and when you make concrete with scoria as the coarse aggregate, the air holes get sealed over by, but do not fill up with, the cement and sand paste. It worked for me. My floor sits on it, the dome is covered with vermicrete, I seem to have no trouble getting the floor very hot.
      Failing that, the dome could be covered with a mix of sawdust and clay, when the sawdust burns away you have aerated clay insulation.

      Comment


      • #4
        Re: Alternative Insulation

        Originally posted by TropicalCoasting View Post
        you can use glass bottles on top or anything that wont melt but traps air.
        Sorry but I still fail to see how glass bottles can thermally insulate, if you heat glass up it glows until it melts, each adjacent bottle would also get hot and so on.
        In the end you would end up with hot glass bottles sucking all the heat away.

        Or am I missing something?
        The English language was invented by people who couldnt spell.

        My Build.

        Books.

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        • #5
          Re: Alternative Insulation

          No, You don't miss much. I stand corrected, you miss, misinformation.

          Comment


          • #6
            Re: Alternative Insulation

            Originally posted by Laurentius View Post
            No, You don't miss much. I stand corrected, you miss, misinformation.

            What the....?
            The English language was invented by people who couldnt spell.

            My Build.

            Books.

            Comment


            • #7
              Re: Alternative Insulation

              Originally posted by brickie in oz View Post
              What the....?
              It means that your statement is true. It means the glass bottles have proven to be a good insulation in the construction of so call earth houses, thick walled(1&2 meters thick) adobe houses, using, straw, bottles, shredded car tires and other things to trap air pockets for insulation. The misinformation is that the insulation properties of those thing applies across the board to heaters, kiln, ovens and furnaces.

              Comment


              • #8
                Re: Alternative Insulation

                [QUOTE=
                If you enclose your dome you can use glass bottles on top or anything that wont melt but traps air.[/QUOTE]

                It is the air that does the insulating. The volume of air inside the volume of a bottle is way more than the volume of the glass. Plus you get extra air spaces between the bottles. It is all about the resulting density of the layer. Glass is not a great insulator on its own but add a large quantity of air to it and it becomes a good insulator. Fibreglass insulating batts, which are made of glass are another good example. Likewise ceramic fibre blanket which uses clay fibres separated by air.neither glass nor clay are wonderful insulators but when combined with lots of air they are.
                If you have free bottles then you have free insulation.
                Last edited by david s; 02-01-2013, 08:21 PM.
                Kindled with zeal and fired with passion.

                Comment


                • #9
                  Re: Alternative Insulation

                  A mate built a corrugated iron ring around his dome and filled it full of stubbies over 1 metre high over the dome.
                  His oven definitely holds its heat

                  Comment


                  • #10
                    Re: Alternative Insulation

                    Originally posted by david s View Post
                    It is the air that does the insulating. The volume of air inside the volume of a bottle is way more than the volume of the glass. Plus you get extra air spaces between the bottles. It is all about the resulting density of the layer. Glass is not a great insulator on its own but add a large quantity of air to it and it becomes a good insulator. Fibreglass insulating batts are another good example. Likewise ceramic fibre blanket which uses clay fibres separated by air.
                    Why can't you just make a Void, its full of air?

                    Comment


                    • #11
                      Re: Alternative Insulation

                      Originally posted by Laurentius View Post
                      Why can't you just make a Void, its full of air?
                      Because as the air heats up it moves around taking the heat with it. It needs a barrier, or better still lots of barriers, to prevent this.
                      Kindled with zeal and fired with passion.

                      Comment


                      • #12
                        Re: Alternative Insulation

                        Originally posted by david s View Post
                        Because as the air heats up it moves around taking the heat with it. It needs a barrier, or better still lots of barriers, to prevent this.
                        This is why double glazed windows are sealed as tight as possible: air is a pretty good insulator, but it does get heated, and if you let that hot air rise out of the way, then cooler air replaces it and that gets heated, etc.
                        End result, instead of a layer of insulating air, you get a current of air cooling things.
                        I reckon a void will work as long as it's sealed to stop air flowing.

                        The medium that traps the air, whether it be aerated concrete, glass bottles, ceramic fibres, scoria, what ever, conducts heat - some materials more than others. The idea though, is that there is not very much of this solid, in relation to the air trapped, so the aerated material should not conduct as much heat as the solid.
                        I believe even loose gravel could be used as an insulator if done right. If all the rocks were the same size, i.e. you screened out a very specific size fraction it could work.
                        Say you put a heap of gravel over a 3/4 inch screen, then over a 1/2 inch screen. If you kept the minus 3/4, plus 1/2 inch fraction, it would be quite uniform, wouldn't pack done much, and would provide lots of air spaces while imhibiting air flow.
                        The other reason you would want the particles all the same size is that this would mean the minimum of particle to particle contact, thus minimising heat transfer from particle to particle.
                        Anyway, this being my theory on insulation, I've been trying to think of some things that might help you out given you can't get even gold old vermiculite.
                        Bottles, yes.
                        Can you get anything spherical, like balls of clay or glass marbles?
                        A layer of say 1/2 inch clay balls or marbles, would have maximum air space, minimum point contact between particles.
                        Last edited by wotavidone; 02-01-2013, 03:15 PM.

                        Comment


                        • #13
                          Re: Alternative Insulation

                          Sorry to butt into the conversation.
                          To consider which insulation material would work, you have to look at its application.
                          -exposed temperature range is probably most important and cycles of temp extremes.
                          Ice is a good insulator (if you use it in an igloo). Outside temp. -40F inside
                          above freezing!

                          Also, you have to consider application. If you put R-30 fiberglas insulation in a wall cavity with drywall on one side and other side open to elements, it is not as good an insulator as it would be if the backside were enclosed with almost anything- even a sheet of "Tyvek" paper.

                          I think the entire issue involves trapping air in a space, and not allow it to naturally circulate. This is accomplished in pericrete, styrofoam, glasswool, sheepswool, ceramic fiber etc. Each material perlite, vermiculite, styrene foam, extruded glass fiber, natural sheep wool fiber, extruded ceramic fiber all do the same thing (occupy a space otherwise filled with air). All are also low density.

                          Back to finding the alternative insulation- anything that can trap air, and not deteriorate from design elements. (temperature, wind, water, sun light etc.) should work. Add to that- the product should not off-gas something that would be dangerous or objectionable. (ie. water buffalo dung)

                          Comment


                          • #14
                            Re: Alternative Insulation

                            Originally posted by Laurentius View Post
                            Why can't you just make a Void, its full of air?
                            Yes it will work if it is fully sealed, which is difficult to do. better still evacuate the air and have a vacuum. The same principle as a vacuum thermos flask which insulate wonderfully.
                            Kindled with zeal and fired with passion.

                            Comment


                            • #15
                              Re: Alternative Insulation

                              Originally posted by wotavidone View Post
                              Can you get anything spherical, like balls of clay or glass marbles?
                              A layer of say 1/2 inch clay balls or marbles, would have maximum air space, minimum point contact between particles.
                              Trouble with solid marbles or solid clay balls is that there is too much density. The only air is in the spaces.The beauty of bottles is that there is a large volume of trapped air inside the bottle.The melting point of glass is around 900c (although every glass is slightly different) this is way hotter than you would ever get on the outside of the inner brick wall so glass is ok in that respect. No chance of them melting.
                              Last edited by david s; 02-01-2013, 09:21 PM.
                              Kindled with zeal and fired with passion.

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