Why is shading particularly important in newly built houses?

Just don't expect too much from it - especially not from the [Kontrollierte-Wohnraumlüftung]. If the air wouldn't get worse, I would even turn off the [Kontrollierte-Wohnraumlüftung] during the day in summer. I currently have it set to run at the lowest level when I'm away.

Yes - in winter you can electrically preheat the fresh air, but it doesn’t work the other way around. If I draw in 34-degree hot air, I also distribute it throughout the house. Then the only option is to turn it off. There could have been a cooling variant, but it would have been expensive and half-baked. The supply air duct could have been routed a few meters through the ground. However, that was out of the question for us anyway, since we are installing both the heating and the [Kontrollierte-Wohnraumlüftung] in the attic. Better to have a proper air conditioner directly - but that is not planned. The [Kontrollierte-Wohnraumlüftung]-main unit has, according to the datasheet, a "night cooling" function, but no one has been able to explain to me what that is and how it works.

Well, the heat exchanger also works in reverse

At night it gets cool outside and inside it is still warmer. That is then the "Bypass" function, so that the drawn-in fresh air is led past the heat exchanger, which is thus bypassed, right?

Yes, but I meant it in relation to daytime with 35-degree warm air.

Right. What is the counterpart to heat recovery? Cold retention? I assume the efficiency is also somewhere around the usual 70 to 90%, so it gradually gets warmer as well. But if you then run the controlled residential ventilation at the lowest setting, hopefully it is enough to maintain tolerable temperatures until the next nightly cooling.