Which heating system to choose when building a house with a heated outbuilding

Hello,

I want to build a house in the near future (about 4 months). The plot is already available (30 x 50m). I want to have a house (about 165m² in Kfw 40 standard) and an outbuilding (about 100m² insulation standard normal with 24er T10 stone) built. The heating system should be in the outbuilding. Of course, the house should be heated and the outbuilding as well. For the outbuilding, a heating capacity of 10-12 degrees is sufficient. Everything should be realized via underfloor heating. Which heating system would you prefer (gas, geothermal...). What should be considered?

Regards Fabian

Doesn't anyone have a suggestion?!

You won't be able to get a general answer. If you want to achieve Kfw40, then you have to see how you can do that, for example with gas.

A planner has to be involved, and no one will do that for free in the forum. I also don't know how the [Nebengebäude] is included.