Air heat pump or use gas and solar?

We are now getting a gas heating system plus solar support including underfloor heating.

Which factors must be considered when designing the underfloor heating to ensure that it is also suitable in the long term in case a heat pump is installed later? I once read somewhere that the underfloor heating must meet certain requirements for this, but I can no longer find what these are. I want to clarify this in good time before installation so that I do not take away any flexibility for the future.

And this is what the heating planning looks like.

However, in the basement, it is still planned that only the room at the top left and the room at the bottom left will be heated. The room in between as well as the room at the bottom right will not be heated.

That also surprises me. Although it is contractually agreed exactly like this, during discussions at the time with other solid house builders it was said that everything must necessarily be heated, otherwise for legal reasons the entire basement stairway from the ground floor hallway would have to be sealed off with a door. But now they do not see it that way. The construction supervisor says he is not an expert in heating matters (it really cannot be that you now also need a heating expert as an additional assessor).

The laying distance must be so close that with a lead temperature of max. 35 degrees the desired temperature is reached. Then it will also work later with the heat pump. In practice, this means a laying distance of max 15cm, preferably continuously 10, in bathrooms also 5cm, if the laying system still allows this.

The reference to the engineers is once again funny. Presumably, the energy consultant is also a TGA planner.

In the contract, we only had two rooms in the basement heated. But then came the heat load calculation. There, every basement room was included and planned with underfloor heating.

Then I was told that this would no longer be changed and would remain as is. Likewise, the original orientation of the underfloor heating, which was initially designed for a brine heat pump, would remain the same - they would not change it again, and thus I would be correspondingly flexible later on.

But now that it suddenly says the rooms will be executed as contractually described, that means for me in reverse that the entire heat load calculation is not correct. It also raises doubts that the underfloor heating will actually be flexibly usable later on.

How do I best play it safe? I had contacted them to please confirm the statement that the underfloor heating will be installed in such a way that a corresponding system change is possible in the future. Let's see if I get anything back on that.

The switch is also "possible" if the flow temperature has to be higher. That just becomes more uneconomical and ecological nonsense. Depending on how it is phrased, this confirmation brings exactly nothing…

What would be your recommendation for action? Nothing has been published yet.

Alex85 has already said everything. Keep the installation distances, preferably also 5-10cm in the edge zones, and it will work out even with the heat pump.