Insulate new construction 36.5 aerated concrete?

we are building without KfW but want to insulate as well as possible.

according to the u-value calculator I have to use 200mm insulation

Good heavens, be grateful that you haven’t made the pact "stick hazardous waste on the house wall in exchange for subsidies." You can also stick half a meter of foam boards on the wall; structurally it can be done, that stuff doesn’t weigh much. In my opinion, that’s foolishness, thinking you can just trap heat like that. In the theoretical calculation, it all works perfectly – but theory also ignores that normal ambient air always has a certain moisture level. That’s state-subsidized mold cultivation, if you ask me. In ten years, houses that have this kind of thing won’t get fire insurance anymore; until then, enough of them will have burned down.

But I find those things a scam. When it’s really cold, you heat with electricity anyway. Is that really eco-friendly?

It doesn’t have to be, because the naïve calculation only concerns "theoretical" savings anyway. Reality just gets in the way, measured values spoil illusions. Scam yes, but sometimes it is "political will."

: In your eyes I may seem like a simple-minded person, as you write, but so far I have gotten through life quite well with the pragmatic attitude "never be the first" and "keep it simple." We have winter, the electricity meter is spinning fast in my daughter's new house, who bought such a pump from Junkers because of the few euros of kfw subsidy. We don't even have a harsh winter in the north, just consistently around 0 degrees since New Year's Eve. And the electricity keeps flowing...

: We have winter, the electricity meter is spinning very fast in the new building ...

Me too .... refrigerator + co. just need electricity.

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 36.5 cm block instead of the 24 cm aerated concrete. The mason doesn’t get paid more per hour and generally prefers and especially faster lays the larger block (apparently done with a crane).

Normal aerated concrete blocks are usually not laid with a crane, as far as I know. Only large prefabricated elements or the significantly heavier limestone blocks.

The insulation value of 24cm PPW2 and 14 cm ETICS is about 0.15 and 36.5cm PPW2 is about 0.23. (U-value)

In practice, however, this hardly makes a noticeable difference, since ventilation losses and losses through window surfaces weigh significantly (!) more.

According to prevailing opinion, the solution without additional insulation is clearly cheaper in the long run, even if a few euros more heating costs occur. The maintenance and renovation effort is significantly lower over the lifespan of the house.

We will also build monolithically.

Normal aerated concrete blocks are usually not laid with a crane, as far as I know. Only large prefabricated elements. Or the significantly heavier KS blocks.

I think the boundary between the 50 and 62.5 cm long aerated concrete blocks determines what is still a "two-hand stone" and when a small lifting device is used.

So it probably has something to do with the human arm span, not just the absolute weight. Harder to grip feels basically heavier.

The heating element is of course not primarily intended to defrost the outdoor unit.

Nevertheless, heat pump + solar thermal is a strange combination. Heat pumps are not really good with high hot water temperatures, ergo buffer tank is stupid. Solar thermal on the other hand needs a large buffer tank. So systems are combined that actually don't fit well together. Better to put photovoltaic panels on the roof and use the generated electricity for self-consumption to operate the heat pump. That fits. Then you don't need a buffer tank.