ᐅ Experience with preheating air in controlled residential ventilation systems?

Hello,
We want to install a mechanical ventilation system with heat recovery in our new build.
We have been considering laying pipes underground as well, to pre-warm or cool the air.
We are building without a basement, and my husband will do the earthworks himself using his own excavator.
Therefore, laying the pipes would be very easy and cost-effective for us.
My husband was wondering if it would be possible to use sewer pipes (KG pipes).
Does anyone know if this would work or has experience with something like this?
Or do the pipes definitely have to be special, purpose-designed pipes?

I would definitely choose a continuous pipe due to radon exposure, not something assembled from parts like PVC sewer pipes.

Well, since continuous operation is usually the case, I don’t see this as a problem. However, besides the type of pipe, you should also consider the slope and drainage to prevent condensation water from accumulating inside.

So you prefer to draw in air at 4°C (39°F) instead of the -2°C (28°F) cold air in winter?
If it is 6°C (43°F) outside during winter, would you still want to draw in air at 4°C (39°F)? This air will be warmed anyway through the heat recovery process...
However, you will need stronger fans to pull the air masses through your ground heat exchanger. Is that really energy efficient?
Pumping cool air into the house in summer sounds good, but the mechanical ventilation system with heat recovery must be properly drained accordingly.
I would discuss the whole setup with a professional (who installs the mechanical ventilation with heat recovery) beforehand.

I vaguely recall some users here in the forum mentioning the use of earth-to-air heat exchangers, and the numbers were different—actually more worthwhile. In winter, the intake air was consistently warmer than the outside air (unlike your example of 6°C (43°F) outside and 4°C (39°F) intake), and this, combined with the summer cooling effect, was quite noticeable. Overall, with such a passive component that doesn’t cost much and requires minimal maintenance, you can achieve a higher level of comfort through improved supply air temperature.

Can someone explain what radon exposure is?