Massive construction in self-contracting & KfW 40

Thanks, :) yes, we have already considered the points you mentioned. But can't contractual agreements be made beforehand with the shell construction company and window installer to ensure corrections if, for example, problems arise during the blower-door test? The general contractors will also somehow secure themselves with the companies involved.

The problem is called "diffusion of responsibility."

With a general contractor (GC), the responsibility lies with the GC, and no matter what and where something went wrong, the GC has to fix it. And if it is contractually agreed, for example, that the house is built to KFW40 standards, then the work ("contract for work and services") remains defective until this is achieved.

If trades each work with their own responsibility somewhere along the line, they can pass the responsibility to each other. This is usually not that significant because the trades are partly independent of each other (for example, if the staircase does not fit, the electrician has nothing to do with it). Precisely with KFW40, this does not apply: if the goal is narrowly missed, it can happen that the trades shift the responsibility to each other.
For example, if the target is narrowly not reached, is it due to the facade? The airtightness? The installed insulation? The windows? The planning (window areas also play a role)? Fundamental decisions (e.g., building without controlled residential ventilation => significantly harder to achieve KFW 40)?

If there are problems that cannot be clearly assigned, this diffusion of responsibility is dangerous.

Especially with the KFW300, a lot of money is at stake due to the interest advantage.

It is possible, but the security here is lower due to the diffusion of responsibility.

We did the same (KFW300 + Z20) and have been doing quite well so far with a "shell construction general contractor" (actually a local shell construction company that also takes over the awarding of contracts after the shell construction). The planning and statics are included, and in our case the structural engineer also does the entire KFW calculation. However, they almost always have an energy consultant on hand who knows their standard setup. For KFW40, they usually also know right away that additional roof insulation will be applied, the wall will be thicker, and the basement will be heavily insulated. When we award the trades ourselves or carry out the work ourselves after the shell construction, the shell builder usually seems more happy than charging an extra fee for it.

Yes, you are probably right. I would really be interested to know how many people build with promotional loans with self-contracting and how many with a general contractor, and what their experiences are like, but maybe someone will still get in touch ;) How extensive is the support provided by the energy consultant? Can you, for example, consult and have them check immediately when the shell is completed and then again when the windows are installed, or don't they do that kind of thing?

Oh, that is interesting, , thanks for the feedback! So the planning was done by the shell construction company directly for you? If you contract the trades yourselves, do you have anything regarding KfW 40 in the contracts with the companies? For example, with the window manufacturer?

Yes, he does that with his consultant. I also find everything else difficult to imagine. The general contractor has to tell the consultant how everything is structured, the consultant has to calculate it, then provide feedback, then it has to be considered what will be done instead, etc.

The tender is done by the general contractor, so I can also award it myself. If it is important (and that is actually only the case for windows and the roof) it is stated there.

We do the controlled residential ventilation ourselves, the consultant wanted the design for that, since he also needs it for the calculation. The same goes for the photovoltaic system.

Are you aware of the costs for the consultant? We were quite surprised when we received figures around €18,000 from several consultants.

How extensive is the support from the energy consultant?

As extensive as you commission him. But please keep in mind that almost anyone can call themselves that. You can be an energy consultant without construction experience. He can check whether the agreed materials were installed. However, most cannot determine if the work is technically correct. Therefore, please have this service phase covered by the architect. My energy consultant, for example, only saw the house for the necessary explanations to KfW and was never on site.

do you have anything about KfW 40 in the contracts

No individual craftsman will take that on. Why should they? You commission a service that must be correctly fulfilled – whether you achieve KfW 40 with it is not the craftsman's problem, but the planner's. Supervised by the architect.