Construction costs are currently skyrocketing

And what are you going to do in July with the estimated 1,500 kWh you generate then? Surely about 1,000 kWh will go into the grid at 6,x cents each...

Our building technician estimated the cooling function via underfloor heating (brine-water heat pump) at around 4k at the beginning of the year, but said that cooling units/air conditioning are much cheaper and more effective. For the cooling function, a number of additional devices are required, such as monitoring of condensate formation and similar. These are probably not to be installed retrospectively? And the effect itself is supposed to be moderate: 1-2° near the floor, from knee height you still move in warm air. So we crossed it off again

Underfloor heating doesn’t help either, does it?
You only end up with warm feet and cold knees, who wants that...

Our building technician also estimated the cooling function via underfloor heating (brine-water heat pump) at around 4k at the beginning of the year, but said that with cooling devices/air conditioning it is much cheaper and more effective. For the cooling function, a number of additional devices are required, such as monitoring condensate formation and the like. These are probably not installable afterward? And the effect itself is supposed to be moderate: the 1-2° near the floor, above knee height you still remain in the warm air. So we crossed it off again

Who cares that warm air rises? Radiant heat is also completely overrated ;-)