A housing assembly for a computer system includes at least one first shielding casing with a first plurality of ventilation openings in an area of a first housing wall of the first shielding casing; and at least one second shielding casing with a second plurality of ventilation openings in an area of a second housing wall of the second shielding casing, wherein a first contact area of the first housing wall of the first shielding casing borders directly on a corresponding second contact area of the second housing wall of the second shielding casing, and at least one of the first housing wall of the first shielding casing and the second housing wall of the second shielding casing includes a recess so that the first plurality of ventilation openings of the first shielding casing is spaced apart from the second plurality of ventilation openings of the second shielding casing.