New single-family house, gas or heat pump, target KfW55

...thank you first of all for the reply, unfortunately I am not much wiser than before :-(

That is usually the case, as essential data, for example from a basic investigation, are not known.

...Two heat pumps for the following reason:...

See post Perlenmann! Moreover, the excessive investment is hardly economically justifiable.

...What matters most to us are the costs,...

Which ones? Investment or capital service for this, consumption costs, or overall economic efficiency?

...Which DIN standard must be used for a heating load calculation?

12831 detailed procedure. If controlled residential ventilation is present, it will be wrong 99.5% of the time ;-)

...Does that mean the heating installer can do nothing with all the data from the calculation?

He can use the component geometry of the outer parts as well as the U-values. The internal heat transfer coefficient for the dimensioning of heating surfaces and hydraulics must be determined by himself.

...The buffer storage ultimately serves as an energy storage for the photovoltaic system and is intended to increase self-consumption.

An air heat pump generates energy at a ratio of about 3.5:1, an electric heating rod 1:1 :-)

...The COP of the heating heat pump is 4.0 at L2/35W according to the manufacturer.
The heating capacity of the hot water heat pump is 2.2kW at L21/W15-55 according to the manufacturer.

Such manufacturer data is as useless as a goiter. The actual annual performance factor is decisive. For this, the characteristic curves of the manufacturers must be evaluated!
Whether an air heat pump is purposeful in a KfW 70 standard, probably only the seller knows ;-)

regards

Hello,

I have two questions.

Currently, I am working on the planning of my single-family house with 171m2 living space in the KfW70 standard.
Through the developer, I would get a gas condensing boiler with solar hot water and a Zehnder ComfoAir residential ventilation system.
Through a friend who is a heating installer, I would get an Ochsner air-to-water heat pump GMLW9 plus VX with split outdoor unit Millennium MSV 14 for heating
and an Ochsner Europa 323DK air-to-water heat pump with integrated residential ventilation. This pump would be installed in the utility room and extracts
warm air from the hallway and bathroom; fresh air is supplied back to the room through membrane flaps on the window.

I get both at the same price.

1. Why do you want to combine radiators with underfloor heating?
2. Do you have your provider’s approval to procure the heat generator on site?

I get both at the same price.

With all due respect – friend who is a heating installer or not, I doubt that both are price neutral. The Ochsner units are significantly more expensive than comparable systems. It only makes sense if the "friend" happens to have these two air-to-water heat pumps in stock because of a mispurchase and is eager to get rid of them at all costs ... at least if these are not used devices.

Best regards from the Rhineland

1. Where does it say that I want to combine radiators with a floor heating? I am only having a floor heating installed. 2. This has all been agreed with the BU and is okay.

Regarding the price: Package 1: Gas condensing boiler with solar for hot water and standard sanitary equipment (I only have the total price) €26,000 Floor heating €5,000 Controlled residential ventilation Zehnder Comfo Air 350 €8,000 totals €39,000

Package 2 Complete including the same sanitary equipment €40,000 I do not have the individual prices here right now.

The pump(s) will be newly ordered from the dealer and are not stock items

Here are the costs of the heat pump system: €21,500 incl. VAT installation and IB
Underfloor heating incl. insulation: €10,000 incl. VAT

who put together your system from ochsner? Do you have a buffer tank included? I have an offer for the GMLW9 and the outdoor evaporator, 1x hot water buffer and 1x buffer tank (necessary for the regeneration of the outdoor unit) at almost exactly 20k€. the HRV is extra for me. Whether it is large enough or not I do not know, it depends on your location conditions etc., therefore I would strongly recommend you a precise performance sizing of the heating system. I come to 6kW for 150m² and 25kWh/a/m² HWB (23HWBref), thanks to my nice climatic conditions, on 6kW hot water + heating power. You can find the characteristic curves of the heat pump on the internet. Under my conditions, I come to about -12°C where the heat pump still operates monovalently. (at least on paper) I combine my heat pump with a 5kWp photovoltaic system, so I can also cool in summer (via underfloor heating + HRV with cooling coil), and then the electricity costs me (almost) nothing. Especially in winter, when the heat pump urgently needs electricity, you get less from photovoltaics because the irradiation is simply worse.

Hello,

....You can find the characteristic curves of the heat pump on the internet...

Where exactly? The performance and COP curves for full modulation are always very interesting! Best regards