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

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