Poroton or lime sand stone

Well, I have aerated concrete in my exterior wall and ALL interior walls with 24 cm calcium silicate. The 'algae growth' is a fundamental problem that occurs with every high-insulation method, whether stone or ETICS. The problem is that the stones on the outside are cooler because less energy penetrates from the inside to the outside, and then the warm air condenses on the surface, which leads to algae growth. I also have the problem (but only on the north wall since no sun warms the stone) even though I do not have an ETICS but an aerated concrete stone.

Thank you, that is valuable information, as I had always assumed the problem only occurred with [WDVS].

One more question - how do the two solutions perform in terms of summer thermal insulation?

"Irrelevant," because you let the heat in through the windows.

With us, it's extremely bad, almost black tiles behind glass. One day on the sunny side without the shutters down and the result is 28°.

If you seal the place completely (shutters down from 6 a.m. on the sunny side), the place stays at almost cool 23°. You just must not open the door, or you'll be overwhelmed.

Completely irrelevant? We currently live in a prefabricated house / timber frame construction (13 years old) and the heat definitely does not only come in through the windows.

But we are talking here about a new building made of KS or Poroton. Not about a 13-year-old prefabricated wooden house.