High Heat Loss Heat Management Discuss High Heat Loss in the Oven Management forums; FWIW, I really think demolition and a rebuild would be the best option. I have been using my oven now ...

[crowtrapper]

FWIW, I really think demolition and a rebuild would be the best option. I have been using my oven now for about 9 months and everything is fine except that heat retention is a bit weak.

Basically I used the FB design for a home built dome but the only thing I skimped on was the floor - instead of a concrete supporting base, then a layer of vermiculite concrete, then a firebrick hearth, which all seemed to be a bit time consuming (ha!) I used AAC panels as a support for the firebrick hearth. Kills 2 birds with one stone, yes? support and insulation? Well, no, not really. The oven works OK but heat loss is far too rapid for my liking, mostly through the floor rather than the dome. The dome is standard FB style and never even gets warm on the outside.

If I fire it up to pizza heat, then rake the fire out, the temperature seems to drop from 350 C down to about 100 C in only an hour or so. Makes long slow cooking a bit problematic. It is OK but only just. Seriously, if this problem was any more severe I would demolish it and start again.

Already I am planning my NEXT oven!

[Mitchamus]

I think the problem seems to be to too short a burn time.

You guys are forgetting that the concrete should work as heat storage.
With that amount of thermal mass, once hot, the oven should stay hot for days! or at least 12 hours....

You should try a burn of 6+ hours. In fact, keep a fire ticking over ALL DAY.
and try again.

You could still be driving out moisture from that amount of mass, which will tend to sap heat from the oven.

Or...

The fire bricks used were insulating rather than refractory bricks.
Which is a knock-down & rebuild situation, but at least you wont have to build the stand!


A good way to test would be to take a temperature reading every 30mins after removing the fire. That's the only way to really see how the thermal mass of your oven is performing.


Don't forget that logically thermal mass and insulation do the same thing,
keep the oven hotter for longer.

Thermal mass stores the heat and radiates it back into the oven - keeping the oven hot.

Insulation stops the heat from escaping - keeping the oven hot.

A well insulated, and well thermal massed oven should perform with similar results as far as heat retention in the oven goes.

The only trade off between the two methods (in terms of heat retention) are fuel efficiency!

(and obviously in turn - heat up time)

[crowtrapper]

Yes, must do a continual measurement to see just how fast the heat goes. Firing time could be a bit of an issue - mostly I fire it up and allow about 3 hours which seems to be plenty; have tried a bigger fire for an hour and a half and no, that was NOT long enough. The surfaces were hot but the heat had not diffused sufficiently into the rest of the structure. So - maybe even 3 hours is not enough either.

One of the best results with our oven was an occasion when I was away and our 25 year old son had a fire in there big enough to smelt steel; he rang me in a panic because he thought he might have broken something; and it was hours before the fire died down enough to get near the oven to cook a pizza. It worked perfectly! and nothing broke! Maybe I should learn from that.