Y-Tong (aerated concrete) - quality building material? (sound insulation!)

Are the differences really noticeable?
Soundproofing Energy loss?

If I had had the space, I probably would have chosen lime sandstone plus double the necessary insulation. But since my house was not allowed to be 1m2 larger
(30% of the property may be sealed), I opted for 17.5 Ytong plus insulation plus facing brick. Completely standard:
Overall thickness approximately 46 cm wall.

I think optimizing already good energy values is something for nerds (personal opinion)
Example: I have my windows tilted open almost 24 hours.
A subfloor insulation pays off after 50 years.

Principle: All new houses have great values as standard, so I don’t have to save 50 euros a year in energy.

Resale value doesn’t care either.
The buyer has to like the house and the location. Whether kw 55 or KW40, I’m willing to bet that for us, that’s a minor issue.

Sound insulation is completely sufficient with PP4 (even sand-lime brick partly has the same values). Thermal insulation is very good. The house breathes. Price-performance ratio is okay. Stability is certain, as it is even suitable for multi-storey construction. This will surely hold our two-storey city villa and the kitchen cabinet as well.

Be careful with synthetic sound insulation values; laboratory measurements and subjective perception are two different things. Sound can only be dampened by mass, and when looking at the density of sand-lime brick vs. Ytong, any discussion becomes unnecessary. We currently still live on a cobbled street in our rental apartment, and it can be disturbing. One doesn't even get used to it after years.

The breathing of an exclusively mineral construction method can also be severely restricted depending on the wall structure (exterior facade paint, interior wallpaper paste). It can also lead to condensation and consequently mold at cold bridges; in that case, the "breathing" won't help you at all. An ETICS (external thermal insulation composite system) is a simple way to avoid cold bridges, I mean simply in the sense that fewer mistakes can happen during construction; the whole house is wrapped like an Amazon package. Pavel can manage this too, even if the foreman is currently at the parallel construction site.

All the other advantages are also present with other materials.

If I had had the space

Well, obviously there was plenty available, because

total thickness about 46 cm wall.

somehow doesn't sound like a space saver at all.

Well, obviously there was plenty of it, because

somehow it doesn't sound like a space saver at all.

As you know, facing is a must for me.
If you want facing, this thickness is standard.

As you know, facing is a must for me. If you want facing, this thickness is standard

But it would be the same with KS. Or do you want to achieve more than the Energy Saving Ordinance?

As you know, facing brick is a must for me. If you want facing brick, this thickness is standard

But then the comparison to the wall construction with ETICS is off. Because you wrote that the insulation thickness would be doubled. That is of course unnecessary and also not very sensible. KFW 55, for example, can be achieved with 17.5 cm of sand-lime brick and 16 cm of WLG 032 insulation. If you replace the sand-lime brick with hollow bricks or aerated concrete, you save a few centimeters.