Insulating Firebrick as a heat break?

[deejayoh]

I'm thinking about vent design and ways to incorporate a heat break.

I see many people have used air gaps, but I am thinking about using insulating firebrick (IFB)

Concept is to use a ~1-2 inch width of IFB between the inner arch and the outer arch.
- in the floor - IFB covered with piece of stainless like Gianni has done
- a layer next to the inner arch, as far up as the vent gap. Probably stagger 1 and 2 inch pieces in order to ensure a good bond with the rest of the arch
- under the WFO side of the chimney support to complete the circuit

This would leave me with a continuous band of IFB between the oven and the vent/landing. Seems like it would work but I have a couple of questions and there are probably other things I have not thought about:

1) is the IFB strong enough to be part of the arch? It wouldn't be carrying all the weight
2) is it too brittle? the way I am thinking about putting it in, It's not going to be very exposed to knocking with pizza peels and such, but if it's super crumbly it would still be a problem. Replacing it would be a huge pain
3) is a couple of inches of IFB enough to make a dent in heat transfer?

Would love to hear opinions. I did a search and found a couple people who mentioned doing things like this, but did not find any good documentation of results.

[david s]

Some folk have used them for this purpose and I think they work ok. But apart from creating insulation to reduce heat conduction, they don't provide an expansion joint to take up thermal expansion. An air gap or vermicrete does however. My solution was to make a lightweight cast entry and an 8mm vermicrete thermal break between it and the outer decorative arch. There are numerous solutions to include this idea, so think about what is happening and work out your own solution.

[deejayoh]

Originally Posted by david s

Some folk have used them for this purpose and I think they work ok. But apart from creating insulation to reduce heat conduction, they don't provide an expansion joint to take up thermal expansion. An air gap or vermicrete does however. My solution was to make a lightweight cast entry and an 8mm vermicrete thermal break between it and the outer decorative arch. There are numerous solutions to include this idea, so think about what is happening and work out your own solution.

Expansion joint. Yes, I see how this could be an issue. I knew there was something I wasn't thinking about!

Thanks

[brickie in oz]

Most of the ovens on the forum dont have an expansion joint and work fine, mine included.