Is the building technology okay?

...Would you also tend towards the solution with the brine heat pump or still stick with a gas condensing boiler system (also with underfloor heating and controlled ventilation/heat recovery)?

The results of the calculations alone provide the answer! Only then can it be reliably assessed which solution is actually suitable or reasonable. This should preferably be carried out by a sales-independent MEP planner.

... I keep thinking about those 60 degrees.

There is a corresponding legionella concept for this.

... The consultant said that one should immediately plan underfloor heating in the designated basement rooms.

He is a sales advisor! ;) If the basement is part of the heated zone, this must be taken into account accordingly in the calculations, including the energy saving ordinance proof.

best regards

Thank you very much for your explanations.

So, a corresponding calculation according to the [Energieeinsparverordnung] must be part of the construction service description or the purchase contract?

...So a corresponding calculation according to the Energy Saving Ordinance would have to be part of the construction service description or the purchase contract?

The proof of the Energy Saving Ordinance is not necessarily required, because without it the general contractor will not receive a building permit. However, it is worthwhile to take a close look to see if any "creative accounting" has been done. Although "creative accounting" helps with various funding applications, it burdens the builder later in operation with considerably higher consumption in some cases. Then good advice is usually expensive. It is very advisable to include advertising statements in the contract! (KfW 70, 55, 1 l house, etc.) the respective requirements are often violated (building law). Together with the specialist contractor’s declaration, the builder then has a good chance of free remedial work later, which would otherwise hardly be possible! ;)
It is advisable to agree the technical parameters from the system dimensioning in the contract. This contractually secures, for example, the prerequisites for a good annual performance factor in the case of heat pumps as heat generators.
greetings

@ €uro

Thank you very much for your well-founded statements. They were a great help to me. I will have the final offer including the construction service description checked by an architect and/or an energy expert.

In my opinion, this would be sensible. Better to spend a few extra euros that might pay off many times over later.

Do you have concrete information on what something like this roughly costs? Wouldn't want to be talking about ...a few thousand €uro + here...

Regards...

...I will have the final offer including the construction service description reviewed by an architect and/or energy expert.

Architects and "regular" energy consultants might be somewhat overwhelmed with building services engineering. For example, an energy consultant who is also an MEP planner would be advisable.

...In my opinion, this would make sense. Better to spend a few extra euros that might pay off many times over later.

Unfortunately, many builders come to this realization too late! When I check systems in practice, I often hear: "Oh, if we had known that."

...Do you have concrete information on what something like this roughly costs? Not that we are talking about ...a few thousand € + ...

For me, this costs about < 1 K€ in total for a "normal" single-family house, of course depending on the scope of services and the building specifics. Geometrically complex buildings are somewhat more expensive, simple ones cheaper.

Best regards

OK, we will really consider it.

We have now also been offered another alternative:
Gas boiler, underfloor heating and ventilation/heat recovery.

If you exclude the ventilation, this option would be about 14,000 Teuros cheaper than the brine heat pump.

In general, the key data are known. In my opinion, the ventilation should be included for ecological and comfort reasons (no mold, no improper ventilation during the heating period, etc.), even though the electricity bill will of course be somewhat higher. According to the seller, about 300 €.

Would the gas boiler instead of the brine heat pump be an adequate option?

Regards...