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Help No Insulation! - Forno Bravo Forum: The Wood-Fired Oven Community

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Help No Insulation!

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  • Help No Insulation!

    Last spring i built a barrell vault brick oven, but i used no insulation.

    I used a structual concrete 3" thick, then I mortared and placed 2.5" thick layer of dense fire brick, and then on top of that i placed another 1.25" dense firebrick loose...

    The barrel vault is made up of 1 layer of 4.5" dense firebrick and then i added another layer of 2.5" dense firebrick over that. So i have a total of 7" of fire brick all the way around the oven vault

    This spring I am thinking of placing 2-3 1" layers of ceramic fiber blanket over the exterior vault bricks, then placing wire mesh and applying stucco to it.

    The only issue i have is my oven floor? I do not have insulation under it.

    My top course floor is loose 1.25" thick firebrick over mortared 2.5" thick firebrick, over 3" structural concrete.

    Can I place insulation under the structural concrete????? Would this help retain heat? I cant remove the 2.5" thick brick because i mortared to structural slab...

    The oven did pretty good last year making pizza, but i need to insulate it to
    make breads.

    Any comments or suggestions greatly appreciated.

  • #2
    Re: Help No Insulation!

    the ideal is to retain heat for a long time concrete will suck the heat out of the brick but you should be fine your not a resterunt do your bread at a lower temp under 500F. you arnt selling them to the public. your next oven build outline the floor with the firebrick and fill level with vermicuulte then put your fire brick splits down for the floor my floor temp the next day is 150-200F. 24hour later. on top of the brick i mixed 7 shoval full of vermicuulite to 1 shoval of portland cement made an oatmeal @ put on top of brick then the wire and stucco then put tile on 2 years later outside temp gets 160 on fire side . when floor is 650F. going on 5 year. i built three so far.

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    • #3
      Re: Help No Insulation!

      If you remove the loose brick and add 2 inches of the insulating board, then replace the 1.25 brick w/ 2.5 brick you would be where many builds are currently at. Would the raised floor cause too many issues? I have no clue what your opening height is. Insulating under your hearth would help but but it boggles my mind how much fuel it would take to get to temp. I am certain heat would escape in other areas but it would be an improvement over what you have.
      Last edited by Les; 01-23-2013, 02:41 PM.
      Check out my pictures here:
      http://www.fornobravo.com/forum/f8/les-build-4207.html

      If at first you don't succeed... Skydiving isn't for you.

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      • #4
        Re: Help No Insulation!

        Did you by chance build this based on plans that came along with a foam form?

        Comment


        • #5
          Re: Help No Insulation!

          Yes I did use the form. The oven takes a few hours to heat up then i usually cook up
          some pizzas with a small fire in the oven. Afterwards, i have baked chicken and potatoes, sausage and potatoes in the oven with no problem with the door closed.

          However, Everything I am reading talks about insulation. SO I am thinking of wrapping the exterior of the brick sides and top with 2-3 layers of the 1" Blanket insulation and then placing stucco over the fiber blanket.

          However, Insulating the floor will be harder. I have 1.25" firebrick over 2.5" firebrick over 3" structural concrete. I was thinking of placing ceramic fiberboard under the structural concrete floor... Not ideal but i think it would help retain
          the heat.

          Trying to retain as much heat as possible...

          What do you guys think???

          Comment


          • #6
            Re: Help No Insulation!

            Originally posted by Wineman73 View Post
            What do you guys think???
            I think you found this forum too late, as I did.
            I tore down my first oven and rebuilt it properly.
            The English language was invented by people who couldnt spell.

            My Build.

            Books.

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            • #7
              Re: Help No Insulation!

              Wineman 73,
              I built the same oven you did. Unfortunately, before finding out that firebrick alone, even at 7", will not hold in sufficient heat for longterm baking. I got varying answers as to how to improve my floor heat retention. I only had the single layer of firebrick ontop of the concrete slab. I ended up putting 1" fiberboard ontop of existing floor, then put a second floor onto with 1.25" firebrick. It did help my floor heat up better. The other issue with the lack of insulation on the dome is also a major problem for me. I've debating tearing the thing down and starting over, but don't have the heart/funds to do so. I have been looking at some other sites on oven building, and even had a phone conversation with the owner of the company "we" bought our foam shapes from. He advised to cover with ceramic fiber blanket, 8lb loft, 2 layers so about 2 inches thick. Render with chicken wire. Then do a light stucko ontop. Wait a day, and do a second layer of stucko. He also discussed bricking up the opening some. If you go to the website now, there are some definite modifications that weren't there when "we" built our ovens. He's offered to waive shipping costs for the blanket. I'm checking on prices elsewhere, but $99 seems to be the going rate. If you email/call him, tell him your concerns/unhappiness, he might do the same for you. Right now I'm debating between the blanket or doing a vermicrete cladding. I don't know which is best but any insulation is bound to be better than what we have now.

              Comment


              • #8
                Re: Help No Insulation!

                That is the worst oven design on the planet (other than the styrofoam form). I wish he would listen, I talked to him and showed him how he could, with a few changes, make it into a workable design.

                Comment


                • #9
                  Re: Help No Insulation!

                  He has actually made some changes to his instructions. Now there is vermicrete under the hearth slab, and also a suggestion for 2" of ceramic fiber covered with chicken wire and stucco. He also added a suggestion for closing up some of the the front of the oven opening. I can add the dome insulation and brick up the front. Can't change much about the hearth. I added 1" fiberboard and a second layer of 1.25 firebrick onto of the existing 3" firebrick floor. I think it helped some. But that's the about it for the floor.

                  I'd love to talk to someone that has their oven listed on his site and see if they are still happy with their oven or if they have some complaints. It'd also be nice to see if anyone has made some of these changes to their existing oven and if they worked. I do know just from my own experimentation, covering to doorway while I'm heating up the oven makes a big difference on getting it up to temp. We shall see. I'll be sure to let everyone know how my experimentation goes. I'm not pulling out the sledgehammer yet.

                  Comment


                  • #10
                    Re: Help No Insulation!

                    The only good thing about his design is that he calls for 2 colors of firebrick so that when someone calls I know immediately what they are building and am usually able to talk them into building an oven instead of a funny looking fireplace.

                    Comment


                    • #11
                      Re: Help No Insulation!

                      If you don't have the heart to tear it all down, consider smashing the floor and adding insulation board under free floating bricks and insulating the vault. You will lose some vault height but it should be worth it. The walls may still be in contact with the slab, but at least the floor will heat properly and minimize heat lost without rebuilding the whole oven.

                      I built my oven with the same form but did not follow any of the directions that were provided. My oven is hearth has 5 inches of perlite under it which I hope will be enough. I did not insulate the concrete under the chimney since I don't expect the chimney to get super hot compared to the rest of the vault. Do you guys see any issue by not insulating the front portion of the chimney? I did add a small gap between the hearth floor and concrete entry way as a thermal break also.

                      The form is nice and simple but as you all said the instructions are crap.
                      Attached Files

                      Comment


                      • #12
                        Re: Help No Insulation!

                        Originally posted by fei8lo View Post
                        I built my oven with the same form but did not follow any of the directions that were provided. My oven is hearth has 5 inches of perlite under it which I hope will be enough.
                        5" is heaps.


                        Originally posted by fei8lo View Post
                        I did add a small gap between the hearth floor and concrete entry way as a thermal break also.
                        Great, that will stop a lot of heat escaping, more ovens should incorporate a TB.

                        Are/did you insulate over the top?
                        The English language was invented by people who couldnt spell.

                        My Build.

                        Books.

                        Comment


                        • #13
                          Re: Help No Insulation!

                          Originally posted by brickie in oz View Post
                          Great, that will stop a lot of heat escaping, more ovens should incorporate a TB.
                          The gap is only 1/16 -1/8 of an inch but that i hope is enough of a thermal break for the hearth. The doorway and chimney still connect the dome and hearth to the entry way slab but I hope this path is indirect enough to minimize heat lose.

                          Originally posted by brickie in oz View Post
                          Are/did you insulate over the top?
                          I plan to insulate the whole oven with perlite. I will get 5 inches around the side and top but only have enough room for 3-4 in the back. I am not sure if the fire curing process should be done first or the insulation poured before firing.

                          I overbuilt as much as I could. 6 inch foundation slab. block wall filled with concrete. Oven base slab another 5 inches of concrete and rebar tying it all together. The oven part on the other hand I have no experience with so I have been planning and engineering. The feedback really helps.

                          Thanks

                          Comment


                          • #14
                            Re: Help No Insulation!

                            Originally posted by fei8lo View Post
                            The gap is only 1/16 -1/8 of an inch but that i hope is enough of a thermal break for the hearth. The doorway and chimney still connect the dome and hearth to the entry way slab but I hope this path is indirect enough to minimize heat lose.
                            With domes its hard to have a proper all inclusive TB, but hey, anything to retain the heat in the oven is great.
                            The English language was invented by people who couldnt spell.

                            My Build.

                            Books.

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