Overview
Thermal mass and insulation are the two primary characteristics that describe an oven's ability to absorb and hold heat, and make it useful for cooking. An oven's thermal mass describes the part of the oven that is heated and provides heat to the oven chamber, while insulation describes the oven's ability to stop heat from escaping. or leaking, out of the oven -- where it is lost.
Thermal Mass
The thermal mass of a wood fire oven can vary widely, from a simple 1 1/2" thick clay shell to a massive 12" thick brick bread oven. When considering which oven is right for your application -- whether it is in your home or in a restaurant, there are a number of factors to take into account.
Too much thermal mass is very bad. Heat, like most things in nature, likes equilibrium. If one side of a thermal mass, such as a block of concrete, is hot and the other is cool, nature will try to balance that heat by moving it from the hot spot to the cool spot -- eventually reaching an equilibrium where everything is just warm.
In a wood fired oven, this means that it is strongly desirable for the thermal layers in an oven's dome and cooking surface to be completely hot when it is time to cook. If they are not, the heat in the oven will continue to "wick" away from the oven chamber, in an attempt to create equilibrium in the whole thermal mass.
For example, if it requires 6 hours to fully heat up an oven's thermal mass, that oven will not cook well for the entire six hours it is heating up. Even though you are adding more and more fuel, the heat is moving away from the oven chamber as fast as you can replenish it. With this design it is virtually impossible to maintain the high heat required for the perfect 3 minute pizza.
At the same time, too little thermal mass can also be problematic. While a thin clay oven shell might heat up quickly, it does not posses the heat holding ability to cook larger volumes of food, larger numbers of pizza, or bread. A thinner oven will quickly start giving up heat as soon as its fire has stopped, creating a range of problems for the chef.
The composition up of an oven's thermal material is critical. Alumina and Silica are two materials that have both high heat conductivity and high heat holding capability. An oven rich in these materials will heat up more quickly, and hold heat longer, than an oven made from clay, brick, or even standard firebricks.
The optimal oven utilizes a high alumina oven interior, backed with a thermal layer that provides high heat retention and lower conductivity. This multi-layer design delivers both very high heat in the oven chamber and the ability to cook large amounts of food without cooling down. By tailoring the thermal mass of the oven to the requirement, either residential or commercial it is possible to product the optimal oven for a range of applications.
An oven built using 2" of engineered refractory is perfect for a vast majority of home and garden applications.
Insulation
While too much thermal mass is bad, there is no such thing as too much insulation. Luckily, through modern manufacturing advances it is possible to readily and cost-effectively insulate a wood fire oven. In fact, it is possible to make insulation cost and space trade-offs for a particular oven installation.
Which is a good thing. As the optimal oven design demands a thermal layer that can be efficiently heated throughout, it also demands that the oven's insulating layers be able to stop the heat in that layer, in order to hold it inside the oven. There are a range of insulating products that you can put to use:
For the dome, FB Blanket, a woven ceramic blanket, is highly efficient, and take up very little space. We provide an ample amount of woven ceramic insulation with each of our ovens.
For Igloo installations, the installer or owner can use vermiculite concrete, in concert with ceramic insulation to create an efficient oven in attractive and small design. For Gabled House installations, loose vermiculite provides a cost-effective layer on top of ceramic insulation.
Under the oven hearth, vermiculite concrete and FB Board , an engineered insulating panel, both provide an effective layer beneath the thermal layers of the oven floor.
|
