Combination of air-to-air heat pump, air-to-water heat pump, solar thermal and photovoltaic system with storage

Do only 8 kWp fit on the roof or how is this value determined? What orientation and roof pitch does your roof have?

yes, of course, a controlled residential ventilation system is installed. However, for heating or reheating the air (besides the heat exchanger), it has an integrated air-to-air heat pump. The exhaust air from this is then also used to generate domestic hot water via an air-to-water heat pump.

Oh, I have never perceived it that way before. Why do they do that? What do you use to heat the house? Only with the air-to-air heat pump, and the air-to-water heat pump is only for hot water?

Does it make sense to frost the air-to-water heat pump with the ice-cold exhaust air from the air-to-air heat pump? The outside temperature MUST always be higher than the exhaust air of any heat pump, right?

For me, this is a very complex system that urgently needs to be questioned! In my opinion, straightforwardness is key in construction. Especially if you are only building KFW55, you should urgently avoid using an air-to-air heat pump to heat the living spaces.

There is a heating coil in the controlled residential ventilation system to prevent freezing. Do you mean that?

The roof is oriented to the south with a pitch of 25° - I know, not optimal, but the gable height is limited by building regulations. A steeper roof would make it tight with 2 full floors. The system will have 24 modules of 340 heat pumps each. The next "expansion stage" from the manufacturer is 10kWp, but apparently, they no longer fit on the roof (~12m ridge x 5m rafters).

Oh, I have never perceived it that way before. Why do people do that? What do you use to heat the house? Only with the air-to-air heat pump and the air-to-water heat pump is only for hot water?

Does it make sense to freeze the air-to-water heat pump with the ice-cold exhaust air from the air-to-air heat pump? The outside temperature MUST always be higher than the exhaust air of any heat pump, right?

For me, this is a very complex system that urgently needs to be questioned! In my opinion, simplicity is key when building. Especially if you are only building KFW55, you should urgently refrain from using an air-to-air heat pump to heat the living spaces.

There is a heating coil in the controlled ventilation system to prevent freezing. Is that what you mean?

So in the original it would be that only the air-to-air heat pump takes over the heating, right. We have additionally planned a wood stove with 8kW heating capacity, which will, in the best case, make the air-to-air heat pump more or less superfluous. The heating coil is also present additionally.

I don't know to what extent one is allowed to name companies/products here, otherwise I could show the corresponding system.

Regards

My urgent advice: leave out the air-to-air heat pump and use the air-to-water heat pump with underfloor heating for both! Air is an extremely poor energy carrier.

If you go on a ski vacation or a long-distance trip in winter and cannot heat every day, then you will be heating with almost 100% direct electricity in cold weather.

Google "Proxon heat pump high power consumption"

I am afraid it is already too late for a change.

According to the Energy Saving Ordinance 2014 calculation, or energy certificate, the house should have a primary energy demand of 14.9 kWh / m² / year, which with ~209m² + 100m² basement (of which actually only 35% is heated) amounts to about 4500 kWh. Minus what is generated by the wood stove as heat.

Then I'll let myself be surprised whether it will really be that bad, I hope not. In spring and autumn, the photovoltaic system will hopefully already provide quite a bit of energy for heating. For winter, of course, it is questionable.