Air-to-water heat pump sizing in new construction

Thanks for the info.
On Monday the installer will probably contact me and I have to decide...
I will ask if Wolf also does it in a "smaller" version...

Ask that, but don't expect too much in response. He will hit you with something that sounds totally logical and you will be verbally checkmated. But be prepared that he will say it’s not enough and actually it’s fine.
The calculations are often only rough estimates and include too much safety margin while rarely considering internal gains, etc.
I would immediately ask if only those two models are available or if you could, for example, take another model from the Wolf range.

Say you would like to have the calculated heating load. If that is not available, then the HT value. Say you have a friend who is an engineer who would like to take a look at it or something.

What surprises me is that the Daikin 8kW is also listed in the Bafa list, or does that not say anything about whether the subsidy will actually go through?

No. That only means that it would basically be eligible for funding. Whether you get a subsidy is calculated individually. With the data of your house, your heat pump, and your location. And the deciding factor is the (calculated) efficiency. It can happen that one heat pump is sufficient and the other is not, but both are on the list.

The official BAFA calculator can be found via search engines and used to calculate yourself. But for that we would first need a few more values from you.

Has it already been clarified whether you are building with controlled residential ventilation? I claim that if this is not the worst wood stud house in Germany in new construction, with the size and location you have, controlled residential ventilation will get you to a heating load under 6kW.

Just as the heating engineer suspects that the Wolf is not sufficient, I suspect that 7kw is also too much.
Therefore, the calculation which you should check.
And if you can choose, select a heat pump that is as little oversized as possible. You don’t need a reserve on 98% of the heating days because the NAT is not reached throughout the whole winter.
That’s why it’s just as important to choose a heat pump that can modulate as far down as possible.
The whole smart home integration is unnecessary fuss. You will need two or three heating periods to optimally adjust the heat pump and then you’ll forget about it until it hopefully needs to be replaced in at least 20 years. That’s smart to me...
Very important, also have the calculation of the underfloor heating handed over to you and check it carefully. You should not accept a flow temperature of 35` or even higher.
Also have the planned hydraulics explained to you. There are still heating engineers who like to install a heat pump with a mixing buffer. A no-go!

Also have the planned hydraulics explained to you. There are still heating engineers who like to install a heat pump with a mixing buffer. A no-go!

Just for understanding, why should no mixing buffer be installed anymore? What should one use instead?

Use the screed as a buffer. With an extra storage you need higher flow temperatures, which in turn lower the COP.

Hi,

thank you very much for the valuable tips. We are building without a ventilation system. I will ask about the HT value. I have now seen that the Wolf is a monoblock unit and the Daikin is a split. Is that still decisive?

We are building without a ventilation system.

If that couldn't become the biggest mistake of the construction.... but apparently you already have several points where things are creaking. First the forgotten ring earth electrode. Then the confusion with the heat pump and now you are also telling us that no controlled residential ventilation is planned...