ᐅ Controlled residential ventilation: Is an air gap under the doors necessary?

Hello everyone,

we are building with a central controlled ventilation system for the living spaces. I have heard several times that the interior doors need to be trimmed by about 1 cm (0.4 inches) after installation to allow sufficient air circulation.

Is this true? And if the doors are trimmed, the bottom edge will be “open,” without any coating or edge banding. Is that not a problem?

How is it handled in your experience?

The doors need to be ordered and installed to the correct size from the start, so you won’t have to shorten them afterward. This has worked perfectly with all our doors.

Doesn’t it cost a lot extra if the doors are ordered to fit exactly?

No, the price was the same. But there should actually be enough space even when installing standard doors.
We got our solid wood doors from the carpenter.

Take a look here, almost the same topic.
In post #13 you can see how we solved it.

Allow me to ask a question here. Does anyone here have experience with the Invisido system from the company Renson and have installed it?

The reason for my question is that a friend is having a controlled mechanical ventilation system installed as part of a renovation, which apparently requires trimming the doors. From what I have read, door reductions of about 8mm (0.3 inches) would be necessary.

He is not very happy with this for aesthetic reasons (but will accept it if there is no other option). An alternative would be soundproof door grilles, which, as it seems to me, would not look very appealing either. Hence the question about the system mentioned above.