ᐅ Environmental heat: how effective is it for properly heating a house?

There is no sharp cutoff, but the greater the difference between the supply and outside temperatures, the less efficient the system becomes. This is basic physics. In an unrenovated building with radiators, you quite quickly reach the point where at best a COP of 2 is achieved.

In a stripped-down house, however, you at least have the advantage of being able to install underfloor heating and properly insulate.

tollpatsch schrieb:

Go troll somewhere else, @SaniererNRW123. It doesn’t matter at all who renovates the house, who is planning what here, etc. I asked a general question and added my requirements (to properly heat the house). I also mentioned the disadvantages I’ve found so far on the topic, namely that these systems don’t perform as well at outdoor temperatures below 0°C (32°F), according to various online sources.

Please quote properly. I have almost 10,000 posts in this forum and have worked in real estate for nearly 30 years. So yes, my questions make sense and are well-founded. But if you think you know everything better and can only behave rudely, then take it elsewhere.

tollpatsch schrieb:

Furthermore, as already stated, there is a heating system present: environmental heat -> ambient air.

So the house is not gutted after all. You originally wrote "it is planned." By you? By whom? Based on which calculations? With what heating design? According to which intended energy performance level of the house? Oh right, those questions don’t matter since the heating system is already there 🙄

tollpatsch schrieb:

If that’s not the case, can you @pkiensch support your thesis with facts? Apparently, most articles online seem to say otherwise. Of course, excluding manufacturer websites that only highlight the positive aspects of their products and omit the negatives.

Every new heat pump in an energy-efficient new build will achieve a COP of 3.5–4, provided it is properly planned. There are other groups where you can exchange information. Links are strictly forbidden here...
For example, there is a study from the Fraunhofer Institute on heat pumps in renovated or partially renovated older buildings, but not at new build standards. The result shows that the electric heating element is almost exclusively only needed because of the legionella prevention program for the hot water or the defrost function (this is also the case with my two heat pumps). So, negligible at around 1% for winter use.
Furthermore—even though coming from the manufacturer—there are datasheets that are reasonably accurate because they form the basis for BAFA funding. Since BAFA also wants to monitor heat pump operation with mandatory heat meters, these datasheets and reported COP values are quite realistic.

Yes, an air-to-water heat pump is a sensible choice, but everything needs to be done correctly for it to operate very efficiently.

First, 28/32mm (1.1/1.25 inch) riser pipes are required. Then, at least 22mm (0.87 inch) supply pipes to the underfloor heating manifolds are needed, with multilayer composite pipes of at least 16x2mm (0.63x0.08 inch) for the underfloor heating itself. In the bathroom, it is best to install all walls with aerated concrete to improve insulation.

The pipe spacing for the underfloor heating should be between 10-15cm (4-6 inches) maximum.

Floor covering should be tiles.

The lowest temperatures for domestic hot water without an electric heating element can be achieved with an instantaneous water heater unit. Our domestic hot water is produced at a maximum of 50°C (122°F). This prevents scaling and saves heating costs for the air-to-water heat pump.

During programming, it is also important to ensure that domestic hot water is generated at midday using photovoltaic electricity. Otherwise, we are cooling the underfloor heating with photovoltaic power during the summer midday hours.

So, there are many details to consider to ensure the system is both cost-effective and comfortable.