Insulate new construction 36.5 aerated concrete?

Unfortunately wrong. Gas condensing boiler with solar thermal system. And insulated floor slab.

Here: 50 cm aerated concrete, with small gas condensing boiler, without solar thermal system, due to 15% rule, insulated floor slab, results approximately in "KfW20" (classified as KfW40)

Dear Sir or Madam,

my construction project is now very concrete. I was just at the energy consultant of the Verbraucherzentrale (1 hour = 10€). He noticed the following:

The exterior wall is aerated concrete PPL 2, d= 24cm, and an ETICS d=14cm. He said you could save quite a bit of money here, with the same insulation value, if you use a 36.5cm block instead of the 24cm aerated concrete. The mason does not get more pay per hour and generally prefers to lay the larger block faster (apparently done with a crane).

Accordingly, my 21,000€ for exterior plaster including ETICS would be reduced to about 10,000€. The 36.5cm aerated concrete costs only 3.40€ more per cubic meter compared to the 24cm (the architect planned a 36.5cm PPL 4 block directly for the basement), which amounts to only about 200€ for the entire house.

Therefore, I would save roughly 11,000€ with the same insulation value.

That would really be too good to be true; can someone here possibly confirm this, or do I have a mistake in my calculation?

Nope. We're building it like that too. Ytong outside 36.5 plus Weber plaster. Gas heating, cells on the roof solar thermal. Fits. Kfw 70 easily manages the house. With this heat pump, it would have been KFW 55. But I think these things are a scam. If it’s really cold, you heat with electricity. Is that really eco-friendly?

If aerated concrete has better insulating properties than Styrofoam, why don't they build an ETICS out of aerated concrete?

No idea. I only know that the energy engineer certified the house as easily meeting [kfw 70]. Thus, construction approved.