We are currently building with Poroton T10 (36.5) without additional insulation. With controlled residential ventilation, LWWP, a wood stove, photovoltaics, and good windows, we easily meet Kfw 70 standards – even without the photovoltaics, it’s no problem. The architect's information is probably sparse because everything can still be discussed and changed according to your wishes. The builder, of course, provides more detailed information as the basis for the contract. Oh yes, I would rather replace the 11.5 cm walls with 17.5 cm bricks or drywall. We have a few of those, and when chiseling slots for electrical work, you can already tell that they simply don’t have the stability of the thicker walls, and depending on what is to be installed later, thicker walls or drywall are recommendable.