An oven having a door assembly adapted to reduce heat escaping from a cooking chamber, the door assembly comprises: a front glass defining a front portion of the door assembly; first, second and third inner glasses disposed behind the front glass; at least one doorframe component supporting the front and inner glasses; a plurality of glass guides (264, 266, 267, 268) integrally formed with the doorframe component for supporting the inner glasses; characterized in that the door assembly comprises: at least one retaining spring comprising an elongate metal strip, the retaining spring being arranged to receive the inner glasses and adapted to constrain movement of the inner glasses, wherein the retaining spring comprises a first insertion portion in which the first inner glass is fixedly inserted, a second insertion portion in which the second inner glass is fixedly inserted, and a buffering portion formed between the first and second insertion portions to function as a buffer between the first and second insertion portions, wherein the first and second insertion portions (282, 284) are different in height from each other, and wherein the glass guides comprise first glass guides for guiding and supporting a disposition of a front surface edge of the first inner glass, second glass guides for guiding and supporting a disposition of upper and lower ends of the first inner glass, and third glass guides supporting dispositions of a front surface edge and upper and lower ends of the second inner glass, the third glass guides being formed above the second glass guides by being twice bent from the door frame component. a front glass defining a front portion of the door assembly; first, second and third inner glasses disposed behind the front glass; at least one doorframe component supporting the front and inner glasses; a plurality of glass guides (264, 266, 267, 268) integrally formed with the doorframe component for supporting the inner glasses; characterized in that the door assembly comprises: at least one retaining spring comprising an elongate metal strip, the retaining spring being arranged to receive the inner glasses and adapted to constrain movement of the inner glasses, wherein the retaining spring comprises a first insertion portion in which the first inner glass is fixedly inserted, a second insertion portion in which the second inner glass is fixedly inserted, and a buffering portion formed between the first and second insertion portions to function as a buffer between the first and second insertion portions, wherein the first and second insertion portions (282, 284) are different in height from each other, and wherein the glass guides comprise first glass guides for guiding and supporting a disposition of a front surface edge of the first inner glass, second glass guides for guiding and supporting a disposition of upper and lower ends of the first inner glass, and third glass guides supporting dispositions of a front surface edge and upper and lower ends of the second inner glass, the third glass guides being formed above the second glass guides by being twice bent from the door frame component. at least one retaining spring comprising an elongate metal strip, the retaining spring being arranged to receive the inner glasses and adapted to constrain movement of the inner glasses, wherein the retaining spring comprises a first insertion portion in which the first inner glass is fixedly inserted, a second insertion portion in which the second inner glass is fixedly inserted, and a buffering portion formed between the first and second insertion portions to function as a buffer between the first and second insertion portions, wherein the first and second insertion portions (282, 284) are different in height from each other, and wherein the glass guides comprise first glass guides for guiding and supporting a disposition of a front surface edge of the first inner glass, second glass guides for guiding and supporting a disposition of upper and lower ends of the first inner glass, and third glass guides supporting dispositions of a front surface edge and upper and lower ends of the second inner glass, the third glass guides being formed above the second glass guides by being twice bent from the door frame component.