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

There is no hard cut, but the greater the difference between supply and outside temperature, the less efficient it is. That is simple physics. And in unsanitary buildings with radiators, you quite quickly reach the point where at best a COP=2 can be achieved. In a gutted house, however, you at least have the advantage that you can install underfloor heating and properly insulate.

@SaniererNRW123, troll somewhere else. It doesn’t matter at all who renovates the house, who plans what here, etc. I asked a general question and supplemented it with my requirements (to properly heat the house). I also mentioned the disadvantages I have found on this topic so far, namely that they don’t perform as well at outdoor temperatures below 0°C – according to various sources on the internet.

Please quote. I have been in this forum for almost 10,000 posts and in the real estate business for almost 30 years. So yes, my questions make sense and are well-founded. But if you think you know everything better and can only behave badly, go somewhere else.

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

So the house is not gutted after all. You first wrote "it is planned". By you? By whom? Based on which calculations? With which heating design? Based on what planned energy standard of the house? Oh yes, the questions don’t matter, since the heating system is already there :rolleyes:

If that is not the case, can you @pkiensch support your thesis with facts? Apparently, the majority of articles on the internet say otherwise. Of course, except for the manufacturers’ sites that only show the positive sides of their products and not the negatives.

Every new heat pump in an energy-efficient new building will achieve a COP of 3.5–4. Naturally, if properly planned. There are other groups for exchanging information. Links here are deadly though...
For example, there is a study by the Fraunhofer Institute for heat pumps in old buildings – renovated/partially renovated, but not at new-build level. The result there is that the heating element is used almost exclusively due to the legionella program for hot water or for defrosting (this is also the case with my two heat pumps). So negligible 1% for the winter. Furthermore – even from the manufacturer – there are data sheets that more or less match reality (they must), since they form the basis for BAFA subsidies. And since BAFA also wants to see how the heat pump runs thanks to mandatory heat meters, the datasheets and the indicated COP are quite realistic.

Yes, air-to-water heat pumps make sense, but everything must be done correctly for it to work very efficiently.

First, you need 28/32 riser pipes. Then correspondingly at least 22 supply lines to the underfloor heating distributors, underfloor heating multilayer composite pipes at least 16x2. In the bathroom, ideally, use a cavity wall construction entirely made of aerated concrete for better insulation.

Underfloor heating spacing 10-15cm max.

Floor covering tiles.

The lowest temperatures for hot water without an electric heating element are achieved with a fresh water station. Our hot water is heated to a maximum of 50 degrees. This prevents limescale buildup and saves heating costs of the air-to-water heat pump.

When programming, care must also be taken to generate hot water at midday with [Photovoltaik] power. Otherwise, this summer we will even cool the underfloor heating at midday with [Photovoltaik] power.

So, there are many details to consider to ensure it works cost-effectively and comfortably.