A method for producing a thermally insulating part having a thermal conductivity less than 100 mW/m.K, at 20°C and in an environment at atmospheric pressure, and further having inner and outer walls , respectively, the method comprising the following steps: - using at least one first and one second metal plates , - hollow-forming the first metal plate to constitute at least one portion of the inner wall of the produced part or of a blank thereof, - hollow-forming the second metal plate to constitute at least one portion of the outer wall of the produced part or of a blank thereof, characterised in that the method also comprises steps: - wherein the hollow-forming of the first metal plate is internally at least locally concave to constitute at least one portion of said inner wall, - wherein the hollow-forming of the second metal plate is externally at least locally convex to constitute at least one portion of said outer wall, - wherein the cavity of the first metal plate is placed inside the cavity of the second plate, thus defining together a double-walled bowl, - wherein, during said formings, the shapes of the first and second metal plates are adjusted such that they can be placed in contact with one another, peripherally, while leaving a space there between, inside said periphery, and - then wherein, the first and second metal plates, which each have a thickness less than 3 mm, are placed in a chamber having a low pressure that is lower than the ambient pressure, thus lower than 10 5 Pa and/or filled with a gas having a thermal conductivity lower than that of air, thus lower than 26 mW/m.K, in which chamber the first and second metal plates are welded together, peripherally, with a continuous weld, so that is created between them, inside said space, an enclosure having a low pressure that is lower than the ambient pressure, thus lower than 10 5 Pa, and/or which is filled with a gas having a thermal conductivity lower than that of the ambient air, thus lower than 26 mW/m.K. - using at least one first and one second metal plates , - hollow-forming the first metal plate to constitute at least one portion of the inner wall of the produced part or of a blank thereof, - hollow-forming the second metal plate to constitute at least one portion of the outer wall of the produced part or of a blank thereof, - wherein the hollow-forming of the first metal plate is internally at least locally concave to constitute at least one portion of said inner wall, - wherein the hollow-forming of the second metal plate is externally at least locally convex to constitute at least one portion of said outer wall, - wherein the cavity of the first metal plate is placed inside the cavity of the second plate, thus defining together a double-walled bowl, - wherein, during said formings, the shapes of the first and second metal plates are adjusted such that they can be placed in contact with one another, peripherally, while leaving a space there between, inside said periphery, and - then wherein, the first and second metal plates, which each have a thickness less than 3 mm, are placed in a chamber having a low pressure that is lower than the ambient pressure, thus lower than 10 5 Pa and/or filled with a gas having a thermal conductivity lower than that of air, thus lower than 26 mW/m.K, in which chamber the first and second metal plates are welded together, peripherally, with a continuous weld, so that is created between them, inside said space, an enclosure having a low pressure that is lower than the ambient pressure, thus lower than 10 5 Pa, and/or which is filled with a gas having a thermal conductivity lower than that of the ambient air, thus lower than 26 mW/m.K. <EOS>