Heat-retention cooking saves cooking fuel because after food has been heated to cooking temperature, it is placed into an insulated box where it will continue to cook until it is done. Retained-heat cooking is often introduced along with solar cooking since it further reduces the use of traditional fuels such as firewood and the use of this method allows much more food to be cooked each day in a solar cooker.
This method of cooking is also known as retained-heat cooking, fireless cooking, hay box cooking, or wonder box cooking. Even it stays hot for hours. Heat retention box have been made using hay, straw, wool, feathers, cotton, rice hulls, cardboard, aluminum foil, Inside I made this on Shopboot machine.