Floor plan planning shortly before submitting the building application

In my opinion, a waste of money, as long as the water from the outdoor faucet can be exempted from the sewage fee by means of a separate meter.

I wouldn’t dismiss it like that, because somehow the rainwater has to be channeled away somewhere.
With us, this "concrete collector" is called a cistern, although it only lets the water seep away and was/is necessary.
For us, this had nothing to do with a need for groundwater, but with disposal...

I wouldn’t dismiss it like that, because somehow the rainwater has to be diverted somewhere. Where we live, this "concrete collector" is called a cistern, although it only lets the water percolate away and was/is necessary. For us, it had nothing to do with a need for groundwater but with disposal...

The thing is called an infiltration shaft - but a cistern for retention can be connected before it.

We wanted to have a geothermal heat pump. As already hinted, the heating engineer was skeptical about that. Today we received the result.

With a heating capacity of 7.9 KW (which seems very high to us), 300 drilling meters are needed (6,300 watts cooling capacity divided by 21 watts per meter extraction capacity). Costs at least € 20,000 net. Due to a depth drilling limitation, 10 x 30 m drillings must be carried out and 10 probes connected. Makes absolutely no sense.

They now recommend either surface collectors or an air heat pump. I find neither ideal but better gas with solar.

Is there a heating load calculation according to DIN 12831 or was it estimated again? For comparison: My acquaintance has a heating load of 5.8KW at -12 degrees design temperature and approximately 200sqm living area. KfW55. Without ventilation. I don't have your data in mind nor your region and KfW standard?

I have already requested the heating load calculation several times. I will do it again now.

It concerns NRW. We are building according to the [Energieeinsparverordnung 2016] without any further additions.

The withdrawal capacity is of course extremely low and a limitation to 30m depth is also problematic. That makes no sense. Where does the knowledge of the withdrawal capacity come from? For NRW you can look online in the Geoportal and obtain an expert opinion for your own location by inserting coins.