ᐅ New Construction on a New Plot Without Children – How Should We Approach It?

Hello,
first, a brief introduction.

We (my better half and main breadwinner^^, 52, and I, 44) are facing a new challenge.

Due to an expected job change (within the same company, so no new probation period, etc.), we expect to move again in about 3 years.

Our child will almost be finished with university by then and will be independent. He will probably stay in our region at first, as he studies in a practical training network and already has a job opportunity lined up.

We built once before in 1996/1997—a small prefabricated house at a fantastic price. There was a great offer for families with a major bank and a regional prefab manufacturer. We were able to buy the land quite cheaply from the municipality back then. Due to relatively high interest rates (compared to now^^), we are now close to paying off the mortgage.

We will be finished with the “new start” almost exactly by then.

The current house has a great layout, and with 107m2 (1150 sq ft) of living space, with little hallway and good room distribution, it was more than enough space for a family with one child.

There were few defects back then, and overall, we were very satisfied with the decision to build a prefab house. We were also a bit lucky because the company went bankrupt three years after we moved in.

About our plans now:

Plot prices in the region we expect to move to are around 40-45€/m2 (about $4.50-$5.00 per sq ft), fully serviced. We do NOT want a huge garden, as we see with our parents that, at a certain age, you just can’t maintain everything as you’d like. 600m2 (about 6500 sq ft), if the layout fits a bungalow on it, will be more than enough for our needs.

We plan about 110-115m2 (1180-1240 sq ft) of living space, all on one level (we’re not getting any younger ;-) ) with a partly covered terrace, possibly a garage or carport, and if the price works out, maybe a partial basement. A basement is not absolutely necessary—we don’t have one now and manage with a crawl space. You learn not to keep everything ;-)

We want a bedroom, possibly with a walk-in closet, a bathroom with bathtub AND shower, a guest room/office, and possibly an additional guest toilet with a shower. Depending on whether there is a basement or not, maybe the option for a sauna (sigh... I've always wanted one^^).

An open space plan (living room, dining room, kitchen) is under consideration.

Of course, I’ve started researching... and it was almost overwhelming... at our time, there were just a handful of well-known prefab companies, some of which actually still exist.

How should we best approach this? I have absolutely no idea about current energy standards, what is possible, what is necessary, and how that might affect related financing (we are calculating about 150,000€ (about $160,000) of own capital, partly from the sale of the current house, if all goes well).
KfW 40/55/70?? Passive house, geothermal energy... until last week, these were all completely new “words” for me, and now I’m starting to read up on them. But how deeply do I need to get into this?

The planned move would possibly be around mid-2018, so there is plenty of time to plan and gather information.

Many things that we added to the current house over time we would like to have again, for example, a large covered terrace with automatic sun protection, solar panels for hot water, a walk-in shower, electric roller shutters, possibly with sun sensors, etc.

Ideally, we would like everything from a single source, as we don’t have much time. Because we cannot be on site all the time (about 300km (190 miles) between current home and new location), we need someone we can 100% rely on (I know, that’s utopia ;-) ).

How would you approach this situation?

Thanks in advance—I’m hoping for one or two tips regarding planning and implementation.

dat Baujulchen :-)