Experience with preheating air in controlled residential ventilation?

Hello,
We want to install a controlled residential ventilation system with heat recovery in our new building.
We were now considering laying pipes underground to preheat/cool the air.
We are building without a basement and my husband is doing the earthworks himself with his own excavator.
Therefore, laying the pipes would be very easy and inexpensive for us.
My husband was wondering if it would be possible to use KG pipes.
Does anyone know if that would be possible or have experience with something like that?
Or do the pipes definitely have to be special ones?

I would definitely use a continuous pipe because of radon exposure, nothing assembled like KG etc.

Well, since it is usually continuous operation, I don't see that as a problem. However, besides the type of pipe, one should also consider the slope and drainage, so that a condensate pool does not accumulate inside.

So you prefer to intake 4-degree air in winter instead of the -2-degree cold air? If it's 6 degrees in winter, do you also prefer to intake 4-degree air? This air is warmed anyway through the heat recovery process,... But you need stronger pumps to draw the air masses through your soil. Is that energetically worthwhile? Pumping cool air into the house in summer sounds good, but then the [Kontrollierte-Wohnraumlüftung] must be drained accordingly. I would discuss the whole thing with a specialist (who installs the [Kontrollierte-Wohnraumlüftung]) in advance.

I vaguely remember that some people here in the forum were using a geothermal heat exchanger, and the numbers were different, namely more worthwhile. In winter, the air drawn in was consistently warmer than outside (so not like your example of 6 degrees outside, 4 degrees drawn in), and this plus the summer cooling effect was quite significant. Overall, with such a passive component, which does not cost much and requires little maintenance, a higher comfort level (supply air temperature) can be achieved.

Can someone tell me what Radon exposure is?