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

Hello forum,

I have been reading here for some time and am very impressed by the quality of some answers, so I hope I will also get the right push.

Currently, I am planning my single-family house with 171m2 of living space built to Kfw70 standard.
Through the developer, I would get a gas condensing boiler with solar hot water and a Zehnder ComfoAir ventilation system.
Through a friendly 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 ventilation. This pump would be installed in the utility room and would extract warm air from the hallway and bathroom; fresh air would be supplied back to the rooms via membrane flaps on the windows.

I get both for the same price.

Zum Haus:

Stepped story, 171m2 living area
Underfloor heating flow temperature approx. 35°C
2-layer masonry construction 17.5 cm Ytong, 14 cm insulation, clinker brick
10 cm perimeter insulation
Triple glazing 6-chamber profile Ug value 0.7

Ergebnis der Energieberatung nach DIN 4108-6 und DIN 4701-10
Annual primary energy demand 56.92 kWh/m2
Transmission heat loss 0.27 W/(m2K)
Building envelope area 534.65m2
Building volume 705.65m2
Heated air volume 536.29m2
Usable floor area 225.81m2
A/V ratio 0.76 1/m
Window area 39.36m2

Base slab U-value 0.23 W/(m2K)
Exterior wall U-value 0.17 W/(m2K)
Wood beam ceiling U-value 0.19 W/(m2K)
Ceiling to outside air upward U-value 0.23 W/(m2K)
Ceiling to outside air downward U-value 0.22 W/(m2K)

Absolute heating demand 10704 kWh/a
Absolute domestic hot water demand 2823 kWh/a

I hope this is enough for now.

Regarding the question:

Which of the above heating models is more sensible?
Are the values acceptable?
With the heat pump model and a 5kWp photovoltaic system, could I possibly achieve KFW 55?

I am already looking forward to the answers.

Thanks
Electrician

One more thing about the heat pump: including cooling function and a buffer tank for the planned [Photovoltaikanlage]

Hello,

....Through the developer, I would get a gas condensing boiler with solar water heating and a Zehnder ComfoAir residential ventilation system.

The usual, where a solar thermal system has to be compulsorily purchased, although it is mostly uneconomical in a single-family house :-)

....Through a heating installer friend, I would get an Ochsner air-water heat pump GMLW9 plus VX with split outdoor unit Millennium MSV 14 for heating and an Ochsner Europa 323DK air-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.

Whether an intake air temperature of -12...-25°C in winter makes sense is something everyone must decide for themselves ;-) Moreover, why two heat pumps and not one air heat pump for heating, hot water and a separate controlled residential ventilation system with heat recovery?

...Result of the energy consultation according to DIN 4108-6 and DIN 4701-10...

These are standardized boundary conditions for primary energy verification, nothing more. It is not permitted to use these for heating sizing!

...Would I possibly achieve KfW 55 with the heat pump model and a 5kWp photovoltaic system?

That depends on where the problem lies! Either Ht´ or qp´´! If qp´´ is the "crucial point," it is relatively certain that KfW 55 can be achieved.
What a buffer tank, which tends to reduce efficiency with heat pumps, has to do with photovoltaics is unclear to me ;-)

Best regards

Hello €uro,

thank you very much for the answer, unfortunately I am not much wiser than before :-(

Two heat pumps for the following reason:
If the heating & hot water demand were to be generated by one heat pump, the device would tend to overshoot due to the 2 different temperatures (35° heating and 65° hot water).
A flow temperature of 35°C can be easily achieved even in the deepest winter.

The hot water heat pump extracts about 20°C warm room air, which means that less energy is required to reach the 65° water temperature, at the same time we solve the issue of residential ventilation.

The costs are especially important to us, I do not want to spend more on the entire heating system than the specification from the [BU] and we have achieved that with this model.

Which DIN standard must be used for a heating load calculation?
Does that mean that the heating installer cannot do anything with all the data from the calculation?

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

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

If you really have a developer, you certainly would not be allowed to have someone else install the heating.

I don’t understand how 2 heat pumps could be cheaper than one slightly larger one.

Regarding the logic: In order for the water heat pump not to have it so hard, it sucks the heat from the house? Where does this heat come from? Right: from the 2nd heat pump that supplies the underfloor heating. Sorry, nonsense! Why actually water at 65 degrees? With an air heat pump it would probably even have to be heated with an electric heater?!

According to Ochsner, no heating element is needed up to 65°C. The second pump is mainly for the [Wohnraumbelüftung]. Heat pump for heating & hot water plus [Wonraumbelüftung] = more expensive?