ovens and earth bag construction

[Annie]

Re: ovens and earth bag construction

Let me restate the question,
I am building a igloo style oven per the forno bravo plans. I am working in limited space and the back of the oven will butt up to a curved mission style earthbag wall. (adobe in sand bags)Unfortunately I built the base and the wall before I knew what the heck I was doing with the oven. I have discovered that inorder to build a 36" oven per the plans, I will have to extend the base with a "landing" in front of the oven door. I'm afraid the look will be funky and unattractive I want the exterior of the oven to blend into the wall behind it and get the oven as far back into the curve as possible. I understand that insulation is very important but is there a way to reduce the exterior diameter without sacrificing insulation???

[dmun]

Re: ovens and earth bag construction

Let's back up a bit. What is the material of your dome? Is there any insulation underneath the cooking floor?

To answer your question, No, adobe has next to no insulation properties. When it finally dries out (12 inches? really?) it will have the same thermal characteristics as concrete.

Remember the FB forum mantra:

Insulate! Insulate! Insulate!

[Annie]

Re: ovens and earth bag construction

Thanks,
I know that adobe is used for ovens here in the west, but have been unclear as to it's insulation ability. (Plenty of thermal mass) So....if I put more layers of blanket would it reduce the over all thinkness of the final oven?

[dmun]

Re: ovens and earth bag construction

If you should ditch anything, I would say it's the one inch of mortar. What's that for? Extra thermal mass? You don't need it. The adobe will have no insulation value, I'd make the wall a little thinner in that area so you can get more insulation blanket in the space. One inch of the blanket just isn't enough to prevent heat loss (and bag burning).

[Annie]

Greetings,
I am building an igloo style oven on an earth bag constructed base. The back of the oven will butt up against a curved earth bag wall. (Earth bags are adobe filled sand bags, 12?thick and are covered with 2? of adobe and 3 coats of lime plaster). I want to construct the dome as close to the wall as possible to give more space in front. I was hoping the final oven would appear to extent out from the wall behind it.

My question is: how close can I set my first course of fire brick to the earth bag wall and how much insulation would be necessary in that area? Could I leave room for the 1? of the mortar and 1? of Insulfrax and then allow the wall to take the place of the 4? of vermiculite?
any input on this would be very helpful!