Central ventilation system - air outlet in the floor or in the ceiling?

Hello house building enthusiasts,

in a construction service description it says: "The supply air is provided through floor air supply outlets with white cover grilles, e.g. in the living room, master bedroom, and children's room (if such rooms are available). By combining supply and exhaust rooms, the hallway is used as an overflow area. This means that the room doors have a gap of about 1 cm above the finished floor."

Now my question would be: Do these floor air supply outlets make sense? Is it about reducing drafts from above? I suspect the solid house construction company uses this as standard because the pipes are installed in the floor (impact sound insulation + heating inside) and the ceiling is not suspended. I would actually prefer supply AND exhaust air in the ceiling (seems more reasonable to me, because if the air comes up from below, furniture or the like can be in the way. But if both are supposed to come from the ceiling, you have to drill a hole through the intermediate ceiling (if you want the outlet at the ceiling in the ground floor and upper floor) or basement intermediate ceiling (if you want the outlet at the ceiling in the basement), right? Many thanks for your advice.

In the other thread this interesting topic was not continued:

I don't like to dig up topics again but I would like to hear arguments why the floor is preferred? Does that then apply to supply and exhaust air? Against the floor would speak the "sucking up" of dust and dust being stirred up and the issue of the furniture.

Source:

My concerns about floor valves were in case something is spilled. But that might be unlikely after all. If vacuuming is enough for cleaning, then great. I did not know that I am allowed to put something on the floor valves. In the bedroom I could imagine a chair, on which you can lay clothes sometimes.
So would you leave all the positions as they are?
In the living room I would move it though. Otherwise there is a draft if you sit on the sofa below, right?
Suspending the ceiling on the upper floor is out of the question for me. Can you also do floor outlets in the dining room and living room? Then you can place a sofa with legs. I need a sofa with legs anyway for my robot vacuum cleaner.
And then a wall outlet in the kitchen, e.g.? Or do you have to make everything uniform on one floor?

Source:

An addition: The issue of drafts has already been discussed here. . So this part of the question is answered. Cabinets and furniture should not pose a problem for floor valves, this has also been clarified in one of the earlier threads.

What I am still wondering is: Are there wall outlet valves in solid construction? Where does the pipe go then?

And: What about the 1 cm door gap? Noise problem? Dust also gets through there...

We once saw this offered by a prefab house builder and inquired about it. It was simply about simplifying the construction effort: The controlled residential ventilation pipes are placed in the ground floor ceiling, with ceiling outlets on the ground floor and floor outlets on the upper floor.

It would make sense to always have the exhaust air at the top, because: Wherever there is moist air, it is also warm (shower/bathroom, kitchen - single toilet/guest WC when you sit and sweat *g*) and it rises upwards. You want to pull the moisture out as well. And what about the basement? Ceiling or floor by default? If you have underfloor heating, certainly in the floor, right?

Hello,
at our place, the exhaust vent on the upper floor in the bathroom was installed in a wall. A small piece of drywall was used there to route the exhaust pipe of the gas boiler to the roof and also to accommodate the ventilation exhaust pipe behind it.

Side effect:
Because this drywall is directly next to our shower, we had a small recessed shelf built in it for shower utensils.

On the upper floor, the supply air vents are also installed in the floor of the other rooms.

Regards,
Michael

Normally, the controlled residential ventilation pipes do not go on the raw floor, as is the case with underfloor heating, but into the raw floor. This is not the reason why the outlets are placed in the floor.

In principle, it always depends on how skillfully the pipes can be installed. The shorter the pipes, the less resistance they have and the less noise is generated by the airflow. Therefore, it can definitely make sense to install the controlled residential ventilation in the floor if this can save several meters of piping. Wall outlets are also an option but require a certain minimum wall thickness. I agree with you regarding the exhaust air because exhaust air openings are usually located, for example, in bathrooms. Here I would definitely prefer a ceiling opening because water can sometimes get on the bathroom floor and, depending on the placement of the opening, could then enter the controlled residential ventilation.

As an alternative to the gap under the door, there are also flat door seals that allow air exchange with the door closed (overflow seals). Be aware that these only allow a certain m³/h, and the rest must pass under the door. Alternatively, overflow openings can also be installed in the door frames. However, these are disproportionately expensive if you have them made.