Heat retention in the Hearth / Firebrick cooking surface

Two questions, one post.

First, for long pizza cooks 20 pizzas…2 hours - does your floor temperature hold enough heat or do you need to bring the fire back over your bricks and bring the temp back up? Assuming 6 minutes a pizza by the time you load, stretch, reload.

2nd. How good is your oven at retaining heat? I get mine well above 1000 but by the next day it is below 300. (Last pizza 9:00 pm, next day check at 10:00 am) Is this because I don’t have a damper? I will say, underneath the oven is warm/hot. I am wondering if I should have added a layer of calcium silicate board

Hi Chris,

Sorry for the delayed response—your post was in a section that doesn’t always notify us. I’ve let @Brickwood know about the problem and moved it to another section.

Yes, you have to shift the fire from side to side to keep cooking with a hot hearth. That’s a given with this type of oven. The hearth will stay way too hot to touch, but you want 700°F+ temperatures on the floor, and that kind of intense heat needs intervals of direct contact with burning coals. It’s normal.

Yes, if you do not have a damper, and if you do not have a gasket around the door, cold air will be drawn from the outside, ventilate your oven, and then be drawn up the chimney and out, carrying heat energy with it. You’re getting okay heat retention considering there is no damper, but if you want to get some benefit from those 1,000°F+ temps on the next day, you do need to stop the flow out the chimney.

As for the floor, are you saying there is NO insulation at all under your hearth? Any of the recommended methods for insulating the hearth should result in little perceptible warming under the slab. On the other hand, if it’s basically brick on top of concrete (or even brick/sand/concrete) you’re going to see that behavior. It will have an effect on how long the floor stays hot (your first question), and the concrete makes a dandy, massive heat sink.

Sorry, haven’t logged on in a couple weeks. I built the base with the 2 inches of vermiculite / portland mix. I have 4 inches of insulation on the oven itself. The outer oven doesn’t get hot at all, but I can feel the warmth under the concrete slab. I should have a damper soon :slight_smile:

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Some warmth under the slab is expected. You mentioned ceramic board in another thread, and I think that would avoid even more heat loss; but it’s not all that much to begin with. The concrete underneath is going to soak up heat wherever it can find it, including from the framing bricks around the borders of the hearth slab. That’s one reason your framing bricks won’t feel warm, because they are on top of bare concrete.

Keeping the hearth floor dry is the bigger issue, and since you have the area underneath it insulated you can focus elsewhere.

Your shell insulation sounds like it is performing well—because you shouldn’t ever be able to tell there is a fire in your oven from touching the outer walls. I sometimes walk around mine after a blazing fire and measure it with the IR thermometer, and unless it was in the sun for a while I get ambient temperature readings from the shell walls.

I’ve checked around, and BrickWood’s price for the door gasket kit is very competitive. A damper is just a little too large to fit in most Christmas stockings, but I’ve heard one might end up under your tree. :slight_smile:

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