Saturday, December 24, 2016

Keeping the Brick Oven Hot

insulation inner door
We tend to believe that the fire we build in our brick oven will keep it hot.  In fact, it is the mass of the oven, and especially, the insulation under and around the oven that keeps it hot.

The three places an oven is apt to lose heat is:
  1. out the flue
  2. through the brick dome
  3. under the floor
Preventing this loss is easy and best done as the oven is built.

Foamglas and two layers of fire brick
Fiber blanket before roof goes on
  • Heat loss out the flue is slowed by the door, and in the case of an indoor oven, by a damper in the flue.  In some cases, an additional door filled with insulation has been made to prolong baking time.
  • As the fire heats the bricks of the dome, the BTU's migrate from the interior surface to the exterior.  If there is little or no insulation there, they keep going, resulting in a rapid decrease in oven temperature.  The heat can be contained by significant insulation.  I use refractory insulation concrete as a first layer over the dome and follow-up with four inches of ceramic fiber insulation.  In ovens with a rectangular enclosure, I sometimes fill the remaining space with vermiculite.
  • Heat will migrate downward through the floor of the oven.  I use 4" of a product called, 'Foamglas'.  It is a rigid expanded high temp glass product and makes the setting of floor bricks easy.

insulating concrete with my handprint signature

Fiber blanket, flue and make-up air ducts

Fill'r up


  1. Hi There
    I noted in one of your posts a comment and picture on a combustion air supply. I have been thinking about this for some time now, but haven't seen anyone else do it. Can you email me? I would love to hear more on how you go about it.

    Bassim Dowidar
    Seattle, WA

    1. Hi Bassim.
      It's quite simple. As I build the masonry between the mouth (inner arch) and the face (outer arch) I leave a passage on either side. This can be a brick width or half a brick width depending on the combustion air needed or anticipated. These channels are then connected using flexible vent pipe to the exterior of the building. Once the pipes are away from the masonry the piping doesn't need to be metal. PVC will do. Wedge shaped brick can be cut to cover the channels when not in use. I believe there is a specific post on combustion air.
      Let me know how this works for you.

    2. This post shows combustion air channels pretty clearly.

  2. Mr David
    I need to build an oven to make New York style pizza, remember that this style has a crust which is crisp along its edge yet soft and pliable enough beneath its toppings to be folded in half, in order to develop these characteristics the oven needs to reach 780+ temperature, and also keep the floor super hot, the pizza should be cooked in 4 minutes at the most, I will like to add a gas burner. could you give me advise how should I make the oven in order to meed my needs.


    1. adolfo alvarez
      los mochis Mexico