The Pizza Oven
On one level, there is really no difference between a “bread oven” and a “pizza oven.” Any bread oven can make pizza. Since a bread oven and a pizza oven are structurally the same, please read “Bread Oven Basics” for background information on traditional wood fired ovens if you are familiar with the details.
Optimizing an Oven for Pizza: The oven vault
This said, an oven optimized for pizza is different from one optimized for bread.
The first difference is the height of the oven vault. Radiant energy, the kind of energy that radiates out of the oven wall onto the top of the pizza is subject to the “inverse square law.” This is one of Isaac Newtons laws of physics. It says that radiant energy increase (or decreases) by the square of the distance. Radiant heat is intense, but the intensity falls off quickly. There is a huge difference in the amount of radiant heat falling on the surface of a pizza when the oven vault is 22 inches high, or 16 inches, or 13.
If your primary reason for buying or building a traditional wood fired oven is to entertain with pizza and a meal, then look for an oven kit or build an oven with a vault in the range of 14 inches. Can you still roast a chicken? Can you still bake bread? Yes, of course. But what your oven will excel at is baking anything that thrives in intense high heat — like sardines, mackerel, red peppers, eggplant, sausage, and of course, pizza. As for bread, it will do fine, when cooled, for the sized loaves most of us make, loaves that are between one and two pounds (500g to 1kg). If your passion were 15 pound (7kg) loaves of rye bread (these bake for a very long time) then the low ceiling height is not right for you.
My direct advice for those of you who, looking themselves in the heart, see pizza, a roast chicken, baked fish, and a few loaves of bread, is to choose an oven with a vault between 13 1/2 inches and 16 inches.
Optimizing an Oven for Pizza: Keep it Small
The best pizza is pizza baked in a ferociously hot oven. I recall once, in Italy, going to a popular pizza restaurant. The night I went the outdoor patio was full of leather-jacketed bikers. Inside, it was lovers and families. Unusually, the piaolla was a woman. This was a big restaurant and they had a huge oven. But half the oven was filled with fire. This oven was the mouth of hell. Two pizzas were cooked at once. Each took less than two minutes. that is how they got the volume through.
Always build the smallest oven that will meet your use. Go for unbelievably hot and speed over several pizzas at the same time.
Optimizing an Oven for Pizza: Keep the Mass Down
What you want is low mass — an oven shell no more than 3 inches thick. There is no reason to heat a huge mass of brick if ones primary purpose is baking pizza. In fact, it is hugely wasteful of time and fuel to fully fire a brick oven just to bake pizza and few dishes for dinner, plus some bread. A brick oven can take hours to bring up to temperature. And then, you have so much heat stored in the walls that if you want to bake anything but pizza you have to wait hours for it to cool down. If you are really going to use your oven, you need to be able to fire it quickly — in no more than 1.5 hours. In urban settings we have to buy the wood. We also have to further split the firewood for optimum firing. There is not reason to spend money or time on heating an oven mass you don’t need to rely on.
Massive ovens are essential to commercial bakers who typically give their oven a booster heat once every 24 hours. For the other 22 hours they bake on the heat stored in the oven walls. But the home cook and home baker doesn’t bake for 24 hours. We bake for a few hours.
Couple low mass with hi-tech insulation
Insulation is the key to making any oven work efficiently, but is crucial to the all-around success of a pizza oven. When firing an oven you want to just be heating the oven, not sky above. The exterior of an oven should not be hotter than the outside air temperature. I have built three ovens, two of refractory concrete and one of fire clay and sand. After a pizza party my oven is 450F the following noon, 325F the noon after that, and still above 200F the noon after that. Insulate your oven, whatever the oven core is made of, with kiln insulation. Just because ones oven is optimized for pizza with a low vault and comparatively low mass doesn’t mean that you can’t follow the ancient traditions of baking on a falling oven by cooking dishes that require less and less heat as the oven cools, ending with dried mushrooms or herbs.