KfW55 radiators + air-water heat pump or gas boiler?

Hello everyone,

the following situation:
1.5 floors
125 sqm
36.5 Ytong
Gable roof with 45° including dormer
a decentralized heat recovery system is also planned.
and if I understood correctly a primary energy demand of 77.3 kWh/m2 or here I have another number 22.2 kWh/m2 according to the Energy Saving Ordinance. I think the second number counts?

We will probably install radiators (underfloor heating is probably already out, reasons are not so important for now) and our general contractor recently said that you could operate the air-water heat pump on the radiators. Now I don't really have much knowledge. I know that with an air-water heat pump you should have as low a flow temperature as possible.

Thus, in the running are an air-water heat pump (rotex HPSU compacte 308) + radiators + a "small" photovoltaic system (I organize this myself)
or a gas boiler + solar panels approx. 5m² (Vaillant auroCompact between 3.3 and 14.7KW size still to be determined including 150 liter stratified storage tank) + a somewhat smaller photovoltaic system (minus space for solar).
What is also not quite clear to me is whether the solar panels are available for heating or only for the domestic hot water.

What would make the most sense given this starting point? Advantages / disadvantages?
My tendency is currently towards GAS even though we still have to calculate more costs for the gas connection.

I have briefly already spoken with the photovoltaic provider... he said in the new 2016 ordinance photovoltaic is also credited... unfortunately he has his briefing only next week and could tell me more details then... then in his opinion the solar would be obsolete and we could install more photovoltaic.

Greetings to all

why no underfloor heating?

Best regards
Sabine

Here too, why not?

HK and air-water heat pump is practically the most unfavorable combination one can have... plus photovoltaic and/or ST...

Does someone have money to burn?

okay - that would mean if I interpret your answer the other way around:

The better combo in this case would be: GAS-Theme

Not necessarily, it just has to fit with the rest of the house... but what definitely doesn't fit are the radiators... because for effective function, radiators either need to be of normal size but then supplied with about 60-degree warm water (which in a Kfw55 house probably means a sauna) or the radiators are supplied with only about 35 degrees, but then have to be about 2-3 times larger than usual to be able to heat the rooms...

And for the rest... more doesn't mean better a little photovoltaic here and some ST there doesn't mean it becomes economical (unless the systems are available at zero cost)

The lower the flow temperature, the more radiators you will need. I see gas in the lead here. It won’t be a sauna, but rather small handy radiators.

But still: Why no underfloor heating?