Underfloor heating or air heating in the new building? (KFW55)

Fortunately, it is not a split device. We would rather not set up an outdoor unit.....that spares our nerves and the neighbor’s.

As far as the demand is concerned, I understood that this device can modulate freely.
Here are some data that you (or others) can probably make more use of than I can.

Cop: 4.0 - 4.2
Standard outdoor temperature: -16°C
Annual performance factor: 4.5
Modulation (depending on system size):
6 kW (from 2-6 kW)
8 kW (from 3-8 kW)
11 kW (from 5.5-11 kW)
14 kW (from 5.5-14 kW)

Whereas we probably need one of the smallest systems with just under 120m² of living space.

Ultimately, it is important to us that the thing is as economical as possible (as far as that is possible with such an air-water heat pump), can later possibly be connected to a photovoltaic system (fortunately that is possible)....yeah and of course, that it lasts as long as possible.

Oh sorry, I had looked at it too briefly, yes of course the device is installed indoors. It has only been on the market for a very short time. But that does not change my general statement. A good heating engineer and a good overall system are extremely important, no matter who manufactures the device. They all heat water in almost the same way. Otherwise, probably the smallest device will actually be sufficient for you. I wouldn’t rely 100,000% on the COP and annual performance factor figures, but that applies to all manufacturers! Regarding the noises: this one then has an air intake and an air outlet grille on the outside wall, air-water heat pumps are never silent anyway, as they have to push large amounts of air through... so the neighbor will always hear something – if the air outlet points in their direction. Be very careful during installation to ensure that especially the air outlet duct is perfectly insulated; if mistakes happen, you will have dark mold walls around it after a few years. I’ve seen it myself. If you still have a few euros left: put photovoltaic panels on the roof right from the start of the house construction. The scaffolding is up anyway, the electrician is in the house anyway, etc...