The present invention relates to a modular Installation assembly (1), at least comprising: a rod-shaped measuring insert (2) for sensing a process variable of a medium, an assembly housing for accommodating at least a part of said measuring insert (2), which housing at least comprises a first housing part (3) and a second housing part (5), a first Chamber provided in said first housing part (3), and a second Chamber provided in said second housing part (5). Further, the assembly housing comprises a sealing element (8) which sealing element has at least one opening through which the measuring insert (2) proceeds, and connecting means (7) for connecting said first housing part (3) with said second housing part (5) via the sealing element (8).