A heating vessel comprises a bottom portion made of conductive material and perimeter wall extending upward from the bottom portion to form a perimeter and covers the vessel such as to form a cavity. The perimeter wall comprises an outer wall and an inner wall, and at least an adiabatic portion defined between the outer wall and the inner wall, which is as an adiabatic layer. The dimension of the inner wall is less than the outer wall. The inner wall is connected to the bottom.