Convection ovens differ from conventional ovens due to the manner in which heat is dispersed throughout the unit. A convection oven works by ensuring an even spread of heat throughout the compartment, allowing all areas of the oven to cook foods at a constant temperature. This is achieved through the use of fans built in to the oven housing, which blow hot air over the surface of the foods. This technique has given rise to these types of ovens known as fan ovens. By utilizing this method of even dispersal, there are no high or low temperature areas as found in conventional ovens, and as a result, cooking times can be reduced, or the overall oven cooking temperature can be lowered, with both operations providing energy usage reduction.
With the fan-assisted hot air movement provided by convection ovens giving a more even heat dispersal, convection oven times are generally less than those cooking times required for conventional ovens. The convection of hot air is only a small part of the cooking technique used in a conventional oven, with the majority of heat being distributed through oven compartment wall radiation. This means that food will cook faster or more slowly depending on its position in the oven. As the heat is evenly spread throughout the oven when using convection techniques, the food will cook more evenly regardless of the position within the oven.
When calculating convection oven times, there is no precise factor that can be applied as the type of food being cooked can alter the time required. As a general rule, when considering a reduction for convection oven times, lowering the conventional oven cooking time by 25 percent will provide a good indication of the timing required for a convection oven. Similarly, when looking to reduce the temperature when using a convection oven, a 25 percent reduction in the specified temperature for a conventional oven will provide an indication of required heat level.
The use of a reduction in convection oven times and temperatures when compared to conventional ovens is usually best taken as a combination of the two reduction factors. That is to say that reducing both the conventional oven cooking time and temperature to establish new convection oven times and temperatures will provide the best overall results. When reducing both temperature and time, the 25 percent factor will still apply but as an overall adjustment. As an example, when reducing convection oven times by 10 percent, the cooking temperature should be reduced by 15 percent.