Air fountain / Drainage pipe for preheating of the return cold water (ZWL)?

I will lay a DN100 rainwater pipe at about 1.7m depth next to an existing shed and next to two planned houses (see sketch). A DN100 drainage pipe with a coconut fiber covering will be placed beside it, with some gravel around it. That means I will dig a trench about 30 m long, 1.7m deep (gradually decreasing), and 0.6m wide and fill it with about 50cm of gravel (with soil on top).

Now I have read about the air well here. The supply air for the residential ventilation is drawn from a drainage pipe, so it is cooler than the outside air in summer (and warmer in winter). Which is basically good, but usually does not make much sense for cost reasons. The air passes through the gravel into the pipe, possibly also via the inspection shafts at the two pipe ends.

Since I am digging my trench anyway, the additional costs are not particularly high: 30m of bare drainage pipe and a few cubic meters more gravel. The excavated soil can be spread on the property.

What do you think about this? And can I possibly save the air conditioning in summer because of this? Is there any reason not to use the pre-tempered supply air for both planned houses? Or is the air exchange rate of a controlled residential ventilation so high that the air in the pipe does not have time to cool down or warm up anyway?

The idea is good, but I am not familiar with the execution. I know of a closed pipe that draws air from somewhere in the garden and is tempered through the pipe wall in the ground.

Either way, I consider this the best implementation of a controlled residential ventilation system. It avoids the typical problems.

Regarding the calculation, I’m out.