Controlled residential ventilation in bungalow: Is it necessary to hang down the ceiling?

Insulate the roof and lay all the piping and the system in the attic

We do the same, it works as well. Nevertheless, I would recommend installing as much as possible in the heated area.
With our controlled residential ventilation, you can see very well from four temperature measuring points how the heat recovery suffers significantly in the deep winter, because the controlled residential ventilation, distributor, and silencer are located in the unheated and insulated area. Retrofitting the insulation is tricky. Without the measurements, admittedly, I would not have noticed it.

We are also building a bungalow with controlled residential ventilation (Zehnder ComfoAir). In our case, the ducts for the supply air are to be located below the screed. The pipes for the exhaust air (bathroom, kitchen, WC) must probably be visibly attached to the ceiling and will be covered with drywall. This solution does not really appeal to me either; I do not understand why these cannot be installed invisibly in the ceiling.

Just install the valves and pipes into the already existing pre-wall installations (WC etc.). This way they remain invisible.

The suspended ceiling also has advantages. For example, if you use the flat oval pipes from the Viessmann controlled residential ventilation system, it adds about 5-7 cm to the installation height under the ceiling.

Advantages I see: pipes do not run through the unheated attic (even if insulated: still colder than the living area).

You can, for example, suspend the ceiling only in the edge areas and thus create nice planes with spot lighting and LED backlighting on the ceiling. Attached is the first best google image of such a ceiling, which practically calls for moving the ventilation system into the luggage compartments:

[ATTACH alt="decke.jpg" type="full"]37119[/ATTACH]

how has the original poster decided now?

Lowering the ceiling probably doesn’t make much difference. See performance specification for a Pluggit Avent C 200

Due to the required minimum clear suspension height of the drywall cladding for the installation of the duct system, the clear room height in all rooms (except HAR) is reduced by 3 to 4 cm.
In the HAR on the ground floor, deviating from § 12 of the construction and performance specification "Insulation and drywall cladding," an OSB panel is installed directly below the vapor barrier.
On this substructure, the air duct system including distribution boxes and silencers are mounted and enclosed by a suspended ceiling construction with double drywall boarding.
The clear room height in the HAR is reduced by approximately 30 cm.

However, I don’t understand why the entire HAR is suspended. You don’t have to ‘enclose’ the controlled residential ventilation.

After we have the ventilation concept from Vaillant and have also consulted with the general contractor, the ceiling will only be lowered slightly and the flat pipes will be installed directly under the vapor barrier.