Installation of controlled residential ventilation - is underground supply air sensible?

I once overheard that it is wise to lead the supply air for the [Kontrollierte-Wohnraumlüftung] a few meters through the ground and possibly through a gravel bed to condition the air.

This should preheat the air a bit in winter and provide pleasantly cooler air in summer.

Now the question is, does the effort really pay off that much and how many meters in length and at what depth should it then be installed??

We were told that it makes sense if you are building with a basement and are already digging a trench anyway. Otherwise, the costs apparently are not worthwhile or the effort was too great for us (additional earthworks, etc.)

Well, maybe I would do it myself afterwards, no idea what length actually makes sense? Does the dehumidification in summer significantly contribute to cooling? I still live in the apartment and board up everything during the day to keep the heat out. If the controlled residential ventilation then runs in the house during the day, that would mean, all the warm outside air is pumped into the house?

We had also considered that, but we were advised against it due to the potential contamination and the lack of possibility for cleaning and maintenance – after all, you don’t just dig up the pipes again.