To Thermal Break or not to Thermal Break? That is the question.

[Les]

Re: To Thermal Break or not to Thermal Break? That is the question.

Since metal conducts heat WAY more than these bricks, is there a real benefit with filling the divide with metal. These bricks can absorb and retain heat pretty well, in regard to conduction, they are pretty poor. I have no doubt that the break will cause no harm (if constructed properly) but no one has posted empirical evidence that it helps. Any one with the break, please document the delta across the divide, with pictures so we can compare ( without the door on, that's just another variable) If the data supports the benefit, we should get it incorporated into the plans. Here is a test I did last week? https://www.youtube.com/watch?v=03Pwaf8NlOU

[stonecutter]

Re: To Thermal Break or not to Thermal Break? That is the question.

Would stuffing the gap with a lean mixture of vermicucrete work?

Sure, but you still should either use metal or rigidizer because its friable.

[Greenman]

Re: To Thermal Break or not to Thermal Break? That is the question.

I used S/S outside the inner dome and vermicrete around the rest of the break. A year on it seems to be fine.

The temp either side of the thermal break convinces me that it works. It is very significant and I am using it again for the oven I am building for my daughter.

[edsiajb]

Re: To Thermal Break or not to Thermal Break? That is the question.

Would stuffing the gap with a lean mixture of vermicucrete work?

[stonecutter]

Re: To Thermal Break or not to Thermal Break? That is the question.

I used rope, so a word of caution. The fibers come off a go airborne, so wear a mask. Then once you stuff the break, coat it with rigidizer or a homemade slurry of Portland/acrylic admix

[SevenAcre]

Re: To Thermal Break or not to Thermal Break? That is the question.

Thank you, this is some great information. It seems like the general consensus is that a thermal break is a worthwhile mod to incorporate into the build. It seems fairly straight forward, just leave a gap of 3/8 inch or so at the reveal where the arch and vent would normally be connected to the oven opening. This can be stuffed with gasket rope along the walls and arch (available readily from Amazon in 6' lengths), and the floor filled with a short length stainless square tube. Benefits are two fold. This will limit heat loss from the oven through the thermal mass of the throat, and reduce stress and cracking in the vent area due to expansion/contraction of the oven. Correct?
Thanks again!
-Jonathan

[kanoer54]

Re: To Thermal Break or not to Thermal Break? That is the question.

I put in a gap (no metal) all the way around, top, sides and bottom and notice about a 180 t0 200F degree difference. If i were to build another WFO again, which I am, I would probably do the same thing again. No scientific back-up, just my gut feeling.

jon

[cobblerdave]

Re: To Thermal Break or not to Thermal Break? That is the question.

G'day
A 36/42in Pompeii is a large mass of brick. Once heated ( and insulated) stays hot for days and more heat than weekend sometimes. I haven't got a heat break and don't think its of real importance to a large oven.
However a smaller oven with a smaller mass I wouldn't mind betting even small savings like a heat break would have a bigger effect.
Just my 2 cents worth
Regards dave

[deejayoh]

Re: To Thermal Break or not to Thermal Break? That is the question.

I used stainless square tubing with a soapstone landing. The stainless is only half a brick deep, and sits on some IFB splits. So really it's a combo of stainless/IFB - but the stainless makes a nice and sturdy break between the soapstone and the firebrick - which is sort of fragile.

[Campmaki]

Re: To Thermal Break or not to Thermal Break? That is the question.

I went with the stainless steel, but used it as a flashing pan in the vent area. At the back edge, between oven floor and vent floor I am thinking of putting ceramic blanket 1 inch thick and covering it some homebrew mortar with sodium silicate added to make it super hard with repeated fires.

[UtahBeehiver]

Re: To Thermal Break or not to Thermal Break? That is the question.

Thin wall stainless steel tubing or channel.

[ugnsnisse]

Re: To Thermal Break or not to Thermal Break? That is the question.

What about the floor? If a door is in place the floor is still ventilating out a fair amount of heat. What (hygienic) material could that crevice be filled with?

[stonecutter]

Re: To Thermal Break or not to Thermal Break? That is the question.

If there is one "Pro" for NOT having a thermal gap, it would be that it is probably structurally stronger to tie the outer and inner arches together with no gap.

I'm not trying to be contrary, but tying the vent arch into the oven opening does nothing to enhance or benefit it structurally. If anything, it's better that the vent arch is independent of the dome and oven opening, either with or without a thermal break.

[boerwarrior]

Re: To Thermal Break or not to Thermal Break? That is the question.

Like Greenman, I put one in (I stuffed gasket rope in the gap), and with my IR thermometer I can measure a big difference between the two sides of the gap. This makes me feel like it is doing something. But honestly my gut tells my that my oven would perform just as well if it wasn't there.

If there is one "Pro" for NOT having a thermal gap, it would be that it is probably structurally stronger to tie the outer and inner arches together with no gap.

[Greenman]

Re: To Thermal Break or not to Thermal Break? That is the question.

I also have nothing to compare my oven to others but the heat difference between one side of the thermal break and the other is significant enough to convince me that it is a good thing. The difference is quite significant so I would use it if i built another oven.