Heat break?

[wlively]

Re: Heat break?

Rodney

IMHO I don't think it is worth the effort. There is so much mass in these ovens that properly insulated, they will retain heat longer than you really need.

The fire break I put into the floor was to keep my entry floor cooler, not to raise thermal efficiency. The amount of floor or entry arch in contact with the dome is very small compared to the area of the dome, so heat leakage is also small, probably in the area of insignificant.

As an example, after a good 2-3 hour pizza burn and another 2-3 hours for the temps to "settle" (brick face temp within 10 deg of center of brick temp) my oven looses 100deg a day (measured constant rate over 3 day period) with the door on.

Insulate your oven well and build a door instead.

This is great! I am at the stage right now where I will start my entry arch and was going to put a 2mm piece of cardboard between the entry and vent which I would remove after.
My theory was that an air gap, be it ever so small would still act as a heat break and I think my entry arch will be strong enough to be self supporting without being keyed into the vent arch.
Am I going down the wrong path?

[Neil2]

Re: Heat break?

I created a heat break at my entry by:

Bottom: a one inch wide ash slot, the width of the door, funneling down to a 4 inch circular opening in the structural slab.
Top: A three inch wide vent opening the width of the entry, funneling up to the flue.
Sides: A 2 1/2 thickness of insulating brick the height of the entry. This is the brick that kiln makers use - check with your local potters.

[Rodneyf]

Re: Heat break?

Cunfusing! I think I will go with no heat break as it sounds like there is no need and only 2 days each weekend to bake so there is no need to keep the oven hot past 2 days. Thanks for your help on this one.

My progress so far.
Picasa Web Albums - rodneyaf - Pizza oven

[stidik]

Re: Heat break?

Mark,
I agree that the entry and entry floor is likely a significant source of heat loss. One consideration would be to use insulating firebricks when building the entry and entry floor. (see Pompeii oven instructions, pg. 62) I don't know if insulating firebricks are difficult to work with or would present other problems along the way. Maybe someone else has used them in the past. I chose to build my entry and entry floor from the regular fire bricks to keep the project as simple as possible.
Good Luck,
Steve Tidik
San Luis Obispo, CA

[GianniFocaccia]

Re: Heat break?

Wow, Wade! 100degrees/day loss sounds very efficient. I am about to pour my foundation slab so haven't gotten too far into this but had this idea: How about placing a 2-3" wide strip of insulating firebrick in the floor the width of the entryway? This could be placed where the vent meets the perimeter of the oven floor and also between the vent landing and the front of the oven where I plan to put an 11x38" piece of granite. Coincidentally, my piece of granite looks identical to yours, Wade. Would yours happen to be flamed?

John

[wlively]

Re: Heat break?

John

No it is std countertop polished finish.

Coincidentally, my piece of granite looks identical to yours, Wade. Would yours happen to be flamed?

John

I haven't seen insulating bricks, so don't know how well they would hold up. The front entry gets allot of use, well with mine anyway.

I wanted to make the break invisible, certain limitations apply then. Can't say it is really worth it, but If you really wanted to, you could make a more efficient floor break by increasing the width. But, I think you could keep it to 1/2 inch and do a better job than I did with the details of the break. Cut both sides of the floor bricks at the break joint at 45degrees to get as wide a gap as possible. Pack the gap with ceramic blanket and or perlcrete and then just enough refractory mortar on top to create a normal looking joint.