KfW70 house, cost comparison of gas condensing boiler and air heat pump, cost comparison of ground-source heat pump

...If the general contractor refuses to carry out the calculation before signing the contract, does it make sense to have the calculation done at your own expense first and then offset it if the contract is concluded?

Primarily with GC/CM, the offer is off-the-shelf, completely independent of whether it meets the individual requirements/necessities. An acceptable GC will not refuse an external calculation/dimensioning, a rather self-interested one, however, will ;-) This is usually where the wheat is separated from the chaff ;-) Therefore, clever builders mostly exclude the trades heating, hot water, ventilation from the outset and outsource these with external planning. Of course, overall somewhat less convenient ;-)

...I assumed that the closer I get to passive house standards in terms of insulation, the less sense an expensive (regarding acquisition costs) but more efficient (regarding variable costs) heating system makes.

The higher the insulation standard of the building, the lower the efficiency requirements for the technology, as absolute values regarding final energy have to be paid.

...conversely, an uninsulated house should receive an expensive but efficient heating system.

Correct!

Hello,

Since there have already been some indications that the decision should only be made based on the energy calculation, here is also the advice that you really get the energy calculation as an essential basis for the decision regarding the heating system. It might be worthwhile to also involve an independent consultant who can better support you specifically on this topic than the sellers or construction advisors of the general contractors. And it certainly makes sense to carry out the energy consultation independently from the general contractor at your own expense if this provides more security for achieving the subsidies and the optimal heating system. Often, such a relatively small investment in the planning phase can bring significant advantages during execution and later use and is therefore surely worthwhile. The exact selection of the system, composed of the essential parts such as investment costs, installation costs, and the later operating and maintenance costs, must also be compared for the device selection; this should already be done in the planning phase and is rarely offered by a general contractor. Therefore, here too, the advice is to demand such a comparison, including the effects regarding the subsidies, from the general contractor or to have it calculated by an external consultant, since quite a lot of subsidies can be lost here.

Best regards