3 the pipe connection moulded part 1 is produced in a combined foaming and casting process in a first mould 9 an inner pipe part 4 having a pipe branch 3 is inserted into the mould 9 the inner pipe part 4 may also be made of metal instead of a plastic the clearance space between the inner pipe part 4 and the inner wall of the mould 9 is filled and foamed in a first method step with a reactive polyurethane foam forming closed cells then after the first polyurethane foam layer 7 has fully reacted the pipe connection moulded part 1 is put into a second mould 9 u2032 which is only slightly larger than the first mould 9 in the second mould 9 u2032 a second layer 8 of a polyurethane casting compound or of another non foaming plastic casting system or of a plastic casting system which does not foam to a considerable degree is inserted into the mould 9 u2032 the material for the casting compound of the outer casing 8 is selected in such a way that the outer casing 8 exerts only a small pressure on the insulating layer 7 instead of a polyurethane system a poly epoxy system or another thermoplastic system for example may.