Environmental heat: how effective is it to properly warm the house?

Obviously, these, at least those that generate heat from the ambient air, only make sense down to 0°C.

Obviously, who says that?
Who rebuilds the house?
Who plans the heating?
What energy level is achieved?
And so on.
I want to buy a car, it doesn't have an engine yet, but I heard that consumption skyrockets above 120 km/h ==> that's the kind of question you asked. Information is needed.

Obviously says who? ...

It is no secret that at subzero temperatures the heating element kicks in with the heat pump. This is 1:1 electric heating, anything but efficient

it is no secret that at subzero temperatures the heating element in the heat pump kicks in. This is 1:1 the electric heater, anything but efficient

That is not a secret, that is simply wrong.

Oh Lord :rolleyes:
There are also existing properties that do not have an energy certificate, for example because they are being converted into residential space and approval procedures are still ongoing. How, where, what, why has nothing to do with the question.

As already described, the property has been gutted. Why it is being sold and whether there are corpses there and if so how many, has nothing to do with the question. Furthermore, as also described, there is a heating system: environmental heat -> ambient air.

A geothermal borehole is probably not possible due to local conditions (distance to neighbor).

troll somewhere else. It absolutely does not matter who renovates the house, who plans what here, etc. I asked a general question and supplemented it with my requirements (to get the house properly warm). As well as the disadvantages I have found so far on the topic, namely that they are no longer so good at outside temperatures below 0°C - according to various sources on the internet.
agreed with that.
Because what use is a heating system that ultimately relies on an expensive alternative (electric heating rod) because it is not designed for the weather conditions (extreme subzero temperatures). Then such a system might make sense in other parts of the world, but not in Germany.

If this is not the case, can you back up your thesis with facts? Because obviously the majority of articles on the internet seem to say otherwise here. Of course except for the manufacturers' sites that only show the positive sides of their products and not the negative ones.

As well as the disadvantages I have found on the topic so far, namely that they don’t work as well at outdoor temperatures below 0°C – according to various sources on the internet.

They certainly don’t work as well at lower temperatures, but the "threshold" of 0°C has no special impact. The rigid statement that this is a hard cut-off at which the heat pump switches off and only the heating rod provides heat suggested to me that there was an obvious misunderstanding of the heat pump’s operation, hence my response.

If this is not the case, can you back up your thesis with facts? Apparently, the majority of articles on the internet seem to say otherwise here. Of course, except for the manufacturers’ sites, which only show the positive sides of their products and not the negatives.

We are in a slight stalemate here; the data sheets with test results according to DIN EN 14511 are often published by manufacturers. Under the search term "A-7/W35" (i.e., providing water with a flow temperature of 35°C at an outdoor temperature of -7°C) you will find the coefficient of performance for various common heat pumps (e.g., Geisha, Arotherm, etc.). In the case of a complete renovation from the shell and proper design of a new heating system, the goal should be to achieve a flow temperature below 30°C, thus the efficiency is even higher. What I find in the data sheets (which I am not allowed to link, but if interested for a particular heat pump it’s easy to research) are COPs of almost 3 or in the high 2,x range. You may assume that in practice it will be somewhat worse than under standard conditions, but even then you are still far from a COP of 1. If you fundamentally don’t trust this data, there is nothing I can do.

It is no secret that at subzero temperatures the heating element in the heat pump kicks in. This is a 1:1 electric heating, anything but efficient

That is simply wrong. A properly designed heating system runs in winter WITHOUT the heating element. Even at -15 degrees, air-to-water heat pumps have no problems with this.
How do I know this? Job, personal experience, forum.

Where did you get your "information"? And what about the answers to my questions regarding further information?