Experiences Single-Family House KfW55 - Assigning Tradesmen Yourself?

Hello everyone,

we are planning the construction of a single-family house in the Stuttgart metropolitan area.
The plot of land is already available.

Currently, we are considering whether to build our single-family house according to the KfW55 standard or "only" according to the Energy Saving Ordinance.

The following is already decided:

Solid house (brick)
Shed roof
Air-water heat pump
Controlled residential ventilation with heat recovery

We now have the following questions:

- Who has experience with how much more complex & expensive it is to build according to KfW55?
thicker bricks, roof insulation, windows, etc.
Costs?

- How would the planning of a KfW55 house proceed?

The current situation is that we already have the finished construction plan (drawn by an acquaintance who is a construction technician).
We need an expert from the KfW list.
What does this expert do then?
Does he then precisely specify to the construction companies which materials, insulation thicknesses, windows, etc. they have to use?
What does the expert's work cost?

All tips and experiences are welcome!
Thank you

For KfW55, there is the procedure based on reference values, meaning that the wall, windows, roof, etc. must not exceed a certain U-value. The additional cost depends entirely on the U-values of the previously planned components (windows, wall, roof, etc.). Then it may be necessary to retrofit accordingly, meaning the insulation value needs to be improved. For the wall, it will then be decided whether to use a thicker or better-insulated brick, or whether to apply an ETICS to the facade. The heat pump and controlled ventilation system are already good for achieving KfW55. I believe our energy consultant wanted about €1000 for the calculation for KfW40. The construction supervision also comes on top of that. Whether the additional cost for retrofitting pays off is something everyone has to decide or have calculated themselves. For me, it was clear that I would go for KfW40 and not build to the minimum standard. Of course, you save heating costs, even if they are certainly manageable. But the house is simply of higher quality, and you never know which standards will apply as the minimum standard in the future, so it might possibly be more difficult to sell it well. You just don’t know any of that.

With KfW, the big question is always whether to have a basement or not.

: with a basement!

: Thanks already for the detailed answer! How did you build? Prefabricated house, turnkey, contracting out the trades yourselves?

We will probably contract out the trades ourselves. I am now wondering if the energy consultant will then create the execution description for the offers of the individual trades for me?

With a basement, the additional costs can become very high. It probably wouldn’t be worth it.

How did you build? Prefabricated house, turnkey, contracted trades yourself?

We built using timber frame construction with a local carpentry and a construction company. We were able to choose the individual trades freely. Or rather, we are still at the beginning, the basement is done so far. The house will arrive in 2 weeks.