Heat transfer metrics - under door heat loss

[fxpose]

I used insulating firebricks for my vent support and in the vent landing area for the thermal break. As these bricks are very brittle I mortared regular firebrick veneers to them as the finished surface.

Edit: Oops...I just realized I already posted an almost identical reply (post #5) to this thread several weeks ago...

[david s]

Because of the rough surface of the insulating bricks and the fact that they abrade easily, they are probably not a good choice for the area in front of the floor. I can see a lot of cheese getting stuck there. They would probably be ok for the sides and the top of the arch though provided you don't keep bashing at them with bits of wood too often.

[SCChris]

I think FX and David have it right, as long as you use the insulating brick in “no wear” zones or veneer them, they should be a fine break. Once you get to the floor, you need to think about durability. The movement of wood going in and cast iron cookware going in and out is going to breakup something that’s too wide or too high relative to the floor or not supported.

The insulating brick is used in kilns and is replaced from time to time when needed, I don't have any idea how it'll hold up over time.

If you use this brick, run it a bit low and use the oven floor to support and protect it. If I build another oven I’ll build the oven separate from the outer arch and isolate with some thickness, half an inch or so, of rigid board. I’d need to inquire about direct flame and the board. It may need a veneer of firebrick to protect it at the arch to chimney transition. I think a veneer over the board could help to integrate the look and protect the board. Remember that an inch of board is equal to 10 or more inches of brick. An inch of Insulating brick is about 7 inches of brick. How the doorway fits into the equation is the next trick. It needs to stop any air and heat flow at the thermal break.


Soap Stone 6.4 W/mK
Brick between 0.98 and 1.13 W/m.K
Insulating Brick at 600F 0.14 W/m.K
Calcium Silicate insulating board at 600F 0.097 W/m.K


Chris

[david s]

Chris,
My solution was to cast the flue gallery in one piece with castable. I designed it quite thin so it doesn't rob too much heat from the dome and I created a heat break between it and the outer arch using a 5:1 vermicrete expansion joint about 10 mm wide.

[Lburou]

Originally Posted by fxpose

I used insulating firebricks for my vent support and in the vent landing area for the thermal break. As these bricks are very brittle I mortared regular firebrick veneers to them as the finished surface.

Edit: Oops...I just realized I already posted an almost identical reply (post #5) to this thread several weeks ago...

Most of the pictures of the heat breaks discussed lately have left me guessing.....Would you be so kind as to post some pictures of the laminated veneer portions of your break? Do you have any intermediate pictures that might show the process you used? I've seen your finished pictures. Thanks George