Congrats, CommanderROR!
Don´t forget so "install" some special features in the house, e.g.:
- Zentralstaubsauger (instead of a common hoover you have one long tube you can put in a counterpart on each floor; dust will be collected in a box in the basement)
- "Wäscherohr" (that enables you to be on the first floor, put your dirty laundry in a pipe and it will come out in the basement, where your washing mashine is located). Unfortunaltely I have not found out any solution that automatically washes the laundry and brings it back to the first floor again
As far as energy / heating is concerned I personally would think about panel heating (Wandheizungen ) instead of usual radiators. Panel heating is no longer reduced to those tiny pipes, now they also offer quite huge flat rectangunlar plates/boards. The climate in a room with panel heating is quite comfortable because of radiant heat (Strahlungswärme) instead of "heated air" (Lufterwärmung). You can have the same effect using a special brick oven (what I mean in that case is called "Grundofen" in German, you can heat an approx. 25 qm room for 8 hours by only using two or three logs).
I´d also think of a bathroom / toilet in the basement - or at least water connections so that you can install a bathroom in a few years (just in case one of your future teenage kids will move in the basement; in that case a seperate entrance to the basement will certainly be appreciated too, so the kids don´t have to come across their parents when they come home late at night, drunk, bringing strange friends... okay, maybe NO seperate basement entrance
Some Chinese companies are developping house paint that changes colors depending on outdoor temperatures. So during winter your house will be darker (to absorb solar radiation) than in summer. I´m not sure whether it´s already available (one year ago they were still in developping status).
I´d also check, whether installing solar is still supported (I think yes, but I´m not sure to what percentage). Same´s for natural oil (Erdgas).
Also check whether the KfW (Kreditanstalt für Wiederaufbau) supports people who build houses (I guess it´s reduced to people who meet all demands of ecological house bulding (ökologisches Bauen)).
Sorry for that many German words, I know forum language is English. But my dictionaries fail completely when it comes to all those technical terms.