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Help! Losing heat like water out of a tap - Forno Bravo Forum: The Wood-Fired Oven Community

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Help! Losing heat like water out of a tap

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  • Help! Losing heat like water out of a tap

    Hi All,
    Can anyone help, we have just had a WFO built, we tried it at the weekend and it was very disappointing. We did manage to cook some pizzas but it was very painful. Our dome cracked! We have zero insulation to the dome .What would be the best solution / materials to be used would insulations quilt be the most practical? Covered with render?
    The base is on a tradition mix of concert! I have got the room to put another layer of fire bricks on top of the ones that sit on of the concert base. Would this be best? Or say a 35mm insulation board and a 35mm brick or just a 75mm brick? Please help if you can.

    Many Thanks, the Rodway’s

  • #2
    Re: Help! Losing heat like water out of a tap

    Sorry to say, it sucks to be you right now. You have the double whammy of no hearth insulation and no dome insulation. It is not an oven, it is a fireplace.
    Here are a few questions and suggestions:
    What is the dome constructed of? How thick? what type of finish? As long as it is not a foot thick, you can add a good layer of insulation and have an effective oven - 3+ inches of refractory blanket or 4+ inches of perlite/portland cement or vermiculite/portland cement. Then a water resistant render layer or 2. As for the crack, ALL ovens crack somewhere, it is going to happen and you can't stop it......Hairline cracks that don't really open up can actually be left alone. Any that open up 1/8" of an inch or more are worth trying to patch, although patching cracks is probably only 50%-75% effective. A properly built dome should remain structurally sound with a few cracks.

    The lack of insulation under your hearth is the BIG issue. Somehow, you need to get at least 2 inches of insulation board directly under the heath bricks and ABOVE the concrete base/hearth support slab. Is your entry tall enough that you can pull out (maybe have to grind and pry) the hearth bricks, add insulation, and replace the hearth bricks? What kind of entry height would you have in relation to the interior dome height if you did this?
    As a last resort if you cannot do the above, do you have access to the underside of the support slab? if so, you could add the insulation directly under the support slab and add a support system to keep it in place. I will warn you, this will leave you with an old school "bread oven" that will require a lot of wood and very big, long firings to heat all of that mass to pizza temps. On the plus side, this would offer alot of heat retention for several bread bakes and plenty of heat for other retained heat cooking. Again, it would require alot of wood and long firings (several hrs), but you could still effectively make good pizza.
    I'm sure others have additional thoughts, this topic used to come up quite a bit. Its a shame you did not find the site before your build.
    I strongly suggest that you visit the Forno Bravo store and "purchase" the Pompeii oven plans (actually they are FREE, FREE, FREE). The plans will show you exactly how your oven SHOULD have been constructed and should give you more insite as to how you may change things based on what you actually have to work with.
    GOOD LUCK and keep us posted.......Pictures would be helpful, add them if you can.

    RT

    Comment


    • #3
      Re: Help! Losing heat like water out of a tap

      Rodway Plazza,

      RT Florida has pretty will summed up your situation.

      The physics of an oven require insulation if you want to get an oven to temperature in a short period of time, and with a 'reasonable' amount of wood. - insulation to separate the fire brick / fire box of the oven from everything else - ie - the supporting structure and all sides and top of the oven.

      Another point worth mentioning is that if this is your first use of the oven, did you go through a complete 'curing' process? A masonry oven is built using lots of water, that then takes a long time to cure and cook from the masonry. It can take a full week or two of curing fires, and as many as a dozen full on pizza cooking fires to get an oven 'cured' to the point it will work consistently well.

      Do download a copy of the Pompeii oven construction plans from this web site, and read - particularly the stuff about insulating. It will help you with some of the details.

      And send along some photo's. We might come up with another idea or two to help get this oven of yours working well.

      They are a ton of fun, and produce great food, so don't give up on your oven! It might take a little work to get it 'dialed in', but so what... it's only work! And then you will have an excellent oven you can use and enjoy.

      Good luck,

      JED

      Comment


      • #4
        Re: Help! Losing heat like water out of a tap

        The thickness of the dome is a fire brick arch and 12mm (ish) of render on top, I do have scope to add installation I think Ceramic fibre blanket would be the best way? Are your thoughts the same how much topping would propose? The height of the entry is around 20’’ and the internal arch around 24’’/26’’, so I guess I could reduce this by an additional layer of fire bricks? Would this help? I can also get to the bottom of the base would it be best to insulated with a ceramic board?

        Comment


        • #5
          Re: Help! Losing heat like water out of a tap

          Sad to hear of your predicament.
          I see the quickest, best and easiest solution is to


          KNOCK IT DOWN, SALVAGE THE BRICKS AND REBUILD IT TO THE FB PLANS.

          Sorry but that is what I would do, (and you might have to to get it to oerform as it should. Anything else will only be a patch up!

          Neill
          Prevention is better than cure, - do it right the first time!

          The more I learn, the more I realise how little I know


          Neill’s Pompeiii #1
          http://www.fornobravo.com/forum/f8/n...-1-a-2005.html
          Neill’s kitchen underway
          http://www.fornobravo.com/forum/f35/...rway-4591.html

          Comment


          • #6
            Re: Help! Losing heat like water out of a tap

            Agree. You need insulation under and around that thing. Time for a mourning beer and a 4 pound maul and chisel.

            Comment


            • #7
              Re: Help! Losing heat like water out of a tap

              I think your dome is actually taller than the FB plans call for- so is your entryway. This means that you can add insulation under your floor as you have proposed. 2 inches is a good amount of the rigid insulation to use.

              You can add the ceramic blanket to the top as well. 2 inches or more would be good. Once that's done, you should see a difference in the heat up time and in the heat retention.

              You can either build an enclosure or put render back over your insulation. I have two inches of ceramic blanket over mine with an additional 3-4 inches of vermiculite concrete on top of that, followed by the stucco (what we call render in the US, apparently).

              As far as cracks go, as long as the structural integrity isn't compromised, spackle over that baby. All domes crack some, as far as I know, and as long as the crack doesn't translate to the outer shell once you've insulated, it should be fine. If you get cracks in that outer shell, fix them promptly or you'll get water damage.
              Elizabeth

              http://www.fornobravo.com/forum/f8/e...html#post41545

              Comment


              • #8
                Re: Help! Losing heat like water out of a tap

                The inner arch should be 63% of the internal oven height, if your higher than this 63% you'll lose more heat out the doorway than you want. If your height is greater than the 63% then you have some room to get insulation under the floor bricks. If your way up there and you can add 3 or more inches of floor then I'd think about 2" of rigid insulation board with half thick firebrick on top. In the US this would add 3.25" of height to the floor without removing the existing floor, not to plans, but it might work for you.. The insulating blanket is the easiest material to wrap a dome shape with and get a good tailored fit. If you're not dead set on having an igloo then a oven house gives you more insulation options and has a better chance of keeping the weather out. Please post photos and measurements.

                Best to you.

                Chris

                Comment


                • #9
                  Re: Help! Losing heat like water out of a tap

                  Where'd you get your oven design from? We should compile a list of offenders. Following bad advice on a project this large is worth making note of so others don't go the same route. Did you use a book people should be warned off of?

                  Website: http://keithwiley.com
                  WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
                  Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

                  Comment


                  • #10
                    Re: Help! Losing heat like water out of a tap

                    Dear Rodway family,

                    As I mentioned earlier, I think you may have the space to bring up the floor and get your insulation. I also want to say, these ovens are very forgiving with regard to design and execution of the design. Whatever happens and you decide to do, I think you can make the oven work for you.

                    Some pizza ovens are built in the afternoon and used in the evening and then torn down. Some of these extreme builds don't have any insulation at all. I wouldn't expect to be able to braise in these ovens, but they work fine for block party pizza. Some primitive ovens in South America are little more than a pile of rocks that contain the fire and retain the heat.

                    Show us what you have and let us give you our opinions as to what your options are / might be.

                    My bet is that things aren't as bad as they might seem.

                    Chris

                    Comment


                    • #11
                      Re: Help! Losing heat like water out of a tap

                      Dear Rodways,
                      I am with Chris. If your internal dome height is 24 inches you should have a entryway height of 15". This gives you some space to either put the insulation board right on top of your cooking floor then another layer of bricks for the cooking floor and have the correct entry height. Then use ceramic blanket on the outside, 3" with a covering of stucco.

                      Or you could follow Neil's advice and have the satisfaction that we all have of having done it yourself and correctly. The actual dome building part is fun and many people on this site who had no previous masonry experience have built ovens- myself included.
                      The oven will perform some better as moisture is cooked out of it, but without insulation the firebricks just radiate heat out to the atmosphere instead of back down onto your pizza. When I was curing my oven before the insulation was on the dome got as hot as 500 degrees on the outside, now it is about 10 degrees above ambient with a full fire going.

                      Good luck,
                      Eric

                      Comment


                      • #12
                        Re: Help! Losing heat like water out of a tap

                        I found this on youtube, they may be able to build you a new oven, as they are in the Uk.

                        YouTube - Bello Forno Wood burning Pizza Oven

                        Comment


                        • #13
                          Re: Help! Losing heat like water out of a tap

                          Many thanks to you all, I am sure that I can do somthing as we have the space within the buildName:  d57a72246299f97f0c468e861b096ea5.jpg
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                          I have attached some photo's Will up date you with what I had done and the outcome. Once again many thanks

                          Comment


                          • #14
                            Re: Help! Losing heat like water out of a tap

                            From what I can see from the pictures it looks like a barrel type oven. This shouldn't change your ability to get some insulation under the existing floor or sandwitched in between the existing and a new higher oven floor. Getting insulation on the outside of the oven won't be to much trouble but water proofing will take a bit of thinking at the chimney end. You folks get a bit rain over there as I understand.

                            Chris

                            Comment


                            • #15
                              Re: Help! Losing heat like water out of a tap

                              Hi
                              We sure do! I think I will put a mushroom type cover over the chimney I think will help reduce the rain that would come down and also give the required ventilation.

                              Comment

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