Placement of the supply/exhaust air valves in the wall?

Hello,

We are building a KfW 70 house with a general contractor and a central ventilation system with humidity recovery. On the upper floor, the ceiling is left open, so the planner can no longer install supply or exhaust air ducts in the ceiling.

His solution (allegedly in consultation with the ventilation installer) is either an air outlet 30 cm above the floor in the wall as a ventilation grille or 2 m above the floor in a typical round shape. He always plans the supply air next to the doors (these are simply the shortest routes for ducts to the room). To me, it looks terrible to always see such a ventilation valve when leaving the room... :eek:

My questions therefore:

[*]Does planning the supply air next to the door (through which the air is normally extracted again) actually make sense? Can the supply air still flow through the room reasonably well here? Where should the outlet ideally be placed? (Originally, I had naively always considered it diagonally opposite the door).
[*]Is supply air through an outlet just above the floor known? And where do these specifications come from: either 30 cm above the floor or 2 m above the floor?

Best regards and thanks! Max

Hello,

...therefore the planner can no longer install supply air or exhaust air ducts in the ceiling.

Basically: not everything that looks appealing or is desired harmonizes with technical functionality or efficiency.

...
He always likes to plan the supply air next to the doors (these are simply the shortest routes to the room in terms of ductwork).

If it is a pure supply air room and the adjacent corridor or similar is an overflow area, "short circuits" can occur and sufficient air exchange is not guaranteed.

Important for GU projects: Have all necessary calculations such as air volumes, heating load, etc. handed over to you.

Best regards