Insulating front of oven landing

[BriggsARNP]

Having not built an oven yet I have a question that I can't find an answer to in the FB plans. I will try to make my self clear. Everyone uses firebrick or some refractory material for their landing. Most people have a firebrick arch covering the vent landing that then transitions to whatever decorative arch is on the front of the enclosure. There is a layer of insulation beneath. Most people don't put any insulation between the fire brick of the vent landing and the concrete or tile or whatever other material is in front of it. Does this area get hot?

[cobblerdave]

My oven has an hearth that extends 400mm (16ins) out from the dome entrance. I insulated mine because... I can remember exactly why now probably just your standard backyard overkill. But I'm glad I did as I oftern keep a fire in the entrance for everone to sit around

Regards Cobblerdave

[Neil2]

I put a one inch gap between the hearth bricks and the landing to act as a heat break. Otherwise, as you note, the landing will heat up considerably.

[Wiley]

The landing will heat up from radiant heat regardless of the heat break.

My landing extends out considerably from the entrance. After a long session of baking pizzas the area directly in front of the entrance on my WFO gets to about 250 F. This is a measurement taken via infrared thermometer several inches out from the opening. At first I was concerned about stresses on the single piece of granite I use as my entrance, but so far so good, no cracking. The slab of granite measures 67 inches long 21 1/2 inches wide and 13/16 inches thick. The portion exposed to the interior at the entrance is 23 inches wide and centered.

Hope this helps,
Wiley

[david s]

I think that one of the advantages of having a heat break, if it is made of material that is somewhat elastic like vermicrete, is that it reduces expansion stresses on the outer parts of the oven. We're always banging on about insulating the oven, yet most designs connect the inner oven to the outer arch without any expansion joint or thermal break.

[ptone]

My vent landing area (casa80) is level with and contiguous with my concrete counter top.

Yes, it gets pretty hot from radiant heat - but not too bad. In a way I don't want to insulate this, as it is not really part of the retained heat system, even though it is conductively connected - I don't consider it strongly linked.

-P

[GianniFocaccia]

We're always banging on about insulating the oven, yet most designs connect the inner oven to the outer arch without any expansion joint or thermal break.

I have two thoughts about this. Regardless of whether or not a landing thermal break exists, the landing and archway will heat up from oven exhaust. This is not necessarily a bad thing.

The reason I designed a thermal break between my oven and archway, including landing, is twofold: stress-relief on oven dome expansion and reduction of residual heat loss through a connected archway.

Heating of the archway from oven exhaust is a reality. Theoretically, since heat transfer rate is partially a function of the difference in temperature of the two materials trading heat, the hotter the landing and archway, the slower the rate of heat transfer from the oven. This would make a case for employing a second outer door even though the vent and flue are still exposed to the elements.

In a way I don't want to insulate this, as it is not really part of the retained heat system, even though it is conductively connected - I don't consider it strongly linked.

I think SCChris studied this and discovered measurable oven heat loss through a contiguous firebrick landing. This loss was further supported by numbers suggesting a higher loss rate with soapstone (6x heat transfer-rate than firebrick). This analysis is what prompted me to design a heat-break in the landing as well as the oven and archway.

http://www.fornobravo.com/forum/f8/h...eat-13372.html (Heat transfer metrics - under door heat loss)

[dmun]

The short answer is that the landing under the vent does get hot. I can fry a pan of Italian sausage bits there while the fire is heating up, just from the radiant heat. I'm not convinced that a thermal break in the floor is advisable, particularly if there is exposed insulation. This area gets a LOT of traffic, with logs, and tools and pans and the tuscan grill sliding back and forth.

If you do a lot of retained heat cooking you might look into a thermal break. For pizza, I wouldn't bother.

[AtTheLake]

How about the outer arch? My original plan was to leave it exposed. We like the look of the firebrick arch. How hot can I expect it to get? Do I need to build another arch out front with a thermal break in between?

Mark

[BriggsARNP]

I am not sure that I have been entirely clear. I understand that the firebrick on the vent landing is going to get hot enough to cook on. I was referring to the area in front of the external arch. Some folks like Dino and the person who did My Old Kentucky Dome have a counter in front of the oven that is usually concrete. I get the feeling that there is sufficient radiant heat from the oven to heat this area up regarless of whether or not there is a heat break. Does that make sense?
Bevan