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

By the way, I have since spoken with our heating engineer, he said that apart from the "normal" air gap under the door, no special ventilation slots or gaps are needed because of the controlled residential ventilation.

Well, that's how it goes with house construction. I was recently at a state building exhibition and lost my faith, or rather was brought down to earth. All (four!) surveyed providers of ventilation systems insisted that the gap under the door is necessary (alternative: leave the door open, grille in the door). Somehow the air has to get through. None suggested frame ventilation or even special drop seals or overflow vents, although I clearly stated that I didn't want a gap under the door.

The ventilation system was calculated by the manufacturer and the airflows were worked out, so they should fit as they are.

The manufacturer will assume in their calculation that the air can overflow unhindered. On-site (!) the overflow has to be ensured. So that doesn't help you at all.

At minimum, I would expect from the ventilation engineer that he a) asks which volume of air is to be transferred and b) asks how wide the door is and then c) reads off the required gap from his table (design according to DIN, which is acoustically really bad).

Better if he proposes alternative measures to you that neither let through excessive light nor sound.

Particularly frustrating is that this topic has been freely available on the internet (in German) for 10 years (?).

I would be interested to know if anyone here has experience with drop-down door seals with overflow function. I keep reading that they exist. But I can't find a single review...

But I can't find a single review...

We have one. It works (I really can't say more).

We have one. It works (that's about all I can say).

That sounds good. Is it by any chance also from planet?