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

I have often written about this. The air outlet in the floor has great advantages regarding pipeline routing and lengths and thus also on installation and operating costs. However, I would always design the exhaust air as a wall/ceiling valve.

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

Throughout the entire house, we have the exhaust air in the ceiling and the supply air in the walls, about 20 cm (center of the disc valve) above the finished floor. Disc valves are installed at both locations. The pipes for the supply air run through the floor and then from there through the 45.5 cm aerated concrete wall.

In the picture, you can see one of the wall connections for the supply air on the upper floor. In the foreground is the connection for the exhaust air in the ceiling of the ground floor below.

: Thanks a thousand for the photo! I’d love to see more of those! That way I can better imagine what it looks like. With 45.5 cm and aerated concrete, there is enough space for the pipe all the way down (up in the attic?) to the room where your ventilation system is located. But with hollow bricks, I’m afraid that probably won’t work, it would crumble, right?

Alternatively to the gap under the door, there are also flat door seals that allow air exchange when the door is closed (overflow seals). Beware, however, these only allow a certain m³/h, the rest must go under the door. Alternatively, overflow openings can also be installed in the door frames. However, those are disproportionately expensive if you have them made.

Very interesting! Do I understand correctly that if there is both supply and exhaust air in every room (including the bathroom), I can seal the bottoms of the doors and thus have more sound insulation?

Very interesting! Do I understand correctly that if there is supply and exhaust air equally in every room (including the bathroom), I can seal the doors at the bottom and thus have more sound insulation?

You understand that correctly, but as a result you will have significantly higher planning and installation costs. However, a room-by-room and demand-oriented design certainly has advantages.

Pragmatically, I would decide based on whether the ventilation is part of the air conditioning.

So if the supply air distributes pre-cooled air in summer, the outlet should of course be at the top.
If it also delivers warm air in winter, then of course the outlet should be at the bottom.

@AxelH. : Thanks a thousand for the photo! More of those, please! This way I can better imagine how it looks. With 45.5 cm and aerated concrete, there is enough space for the pipe all the way down (up into the attic?) to the room where your ventilation system is located. But with hollow bricks, I’m afraid that won’t work, it will crumble, won’t it?

Hello HoisleBauer22,

the aerated concrete blocks were really only slotted from the height of the raw floor up to the branch for the disc valve. Hollow bricks (about which I have no experience) can surely be done with the use of a grinder. All other pipes are under the screed. From the upstairs bathroom, it then goes down behind a drywall partition.



Here is a photo from the ground floor bathroom, where you can clearly see the pipes lying in front of the wall.


Everything here has also disappeared behind a drywall partition.



Under the two bathrooms is the technical room in the basement, where all pipes come together and are connected to the ventilation unit (on the left on the wall in the picture; the drain pipe is for condensate).