COB + Insulation

[Jaycw]

Hi,

Im interested in building a cob oven in my courtyard , have the space all picked out... Im just wondering if anyone could let me know what the external heat is like when its lit? (Or the best way to insulate to avoid it getting hot on the outside when lit) ....

Ive seen some ovens built of refractory mortat etc and they cover them in ceramic fibre blankets to insulate and keep the outside cool , is that a possibility with cob too??

[Wiley]

Re: COB + Insulation

I have two neighbors with cob WFOs. Depending upon how long they are fired the outside can become warm to hot to the touch. I have not seen either of the WFOs get so hot that a momentary contact would sear or even burn to the extent of a blister. Not saying that one couldn't fire them long enough and hot enough to cause such to occur or that one couldn't be constructed thin enough to cause issues, just that in the normal course of events I don't think it is a major problem.

As for using insulating cob ovens with ceramic fiber blankets: One of the major pluses of a cob WFO is their relative low cost to build. They are rather delicate (at least in comparison to a brick WFO) and so depending upon the use and abuse they need rebuilding occasionally. So, to use an expensive insulating blanket on a inexpensive WFO is sort of an oxymoron, especially as reusing the blanket when rebuilding the WFO would be problematic. Would one consider putting a thousand dollar paint job on a hundred dollar car?

Hope this helps,
Wiley

[Jaycw]

Re: COB + Insulation

Thanks for the reply and the info.

I guess my major concern and reason for asking about the outside heat is the positioning of where I want to put my oven.

My yard is quite small so don't have as much of the luxury of positioning that I would like to have.... I want to construct a 1m x 1m brick column to build the oven on ... Only thing is it will be right between a pine deck and a colorbond (metal) fence.... Do you think the heat from the oven is going to cause any major dramas with either of these structures?

[dmun]

Re: COB + Insulation

It's best not to have the mouth of your oven face the pine deck. These things do spit cinders when you're firing them up, and you may have better things to do than stand guard with a spray bottle in the time it takes to heat it up.

[Wiley]

Re: COB + Insulation

Depending upon what the distances are when you say "right between". I don't think there would be any problem with regard to radiant heat from the sides or back of the WFCO (Wood Fired Cob Oven) if a reasonable distance is maintained (think along the lines of building code distances). However, with regard to the radiant heat and the possibility of embers and sparks out the front I have more concern if it were to face toward the pine deck and the distance was short. But, of course one would think that you would want the WFCO facing toward the deck for access etc and so I would take some sort of precautions regarding sparks etc. if you are going to have the WFCO close to the deck.

The fire and radiant heat out the front of a WFCO is impressive due to lack (usually) of a chimney when firing up.

Hope this helps,
Wiley