Blower-Door-Test result (n50=1.13)

Exactly, not good... I have to be able to do something to improve the value, right?!

First of all, I would calculate how much energy is actually “lost” due to the “leak”. Then extrapolate that with realistic price developments for heating energy costs over the planned service life of the house. That way, you get an amount that you can spend on possible improvement measures. Naively calculated.

I was thinking about hiring an engineer from the city to look for further leaks...

Let’s assume a cheap building physicist without measurement technology. He will hardly charge less than €120 per hour. That equals three monthly installments for gas in my plain energy saving regulation shack.

Yes, KfW 40 with a ventilation system. Yes, exactly, not good... I have to be able to do something to improve the value, right?!

I don’t understand: the tangible and visible defects are fixed during the BlowerDoor test, or they are detected and then corrected.
For example, during the process with the drywall installer, holes were sealed. A roller shutter box was leaky and was fixed later. The missing windowsills certainly also pushed the value up a bit. Nevertheless, an average good value came out.

I don’t want to dive into the standards now, but Google tells me that the maximum value would be 1.0 for new buildings with room air technology systems!?

Wasn’t it 1.5? Hm...
As far as I know, it’s only pass or fail. In the latter case, a second BDT is carried out after finding the drafts and treating them.

Do you already have windowsills???
Would there be other consequences because of Kfw40 or something for you, or does it just annoy you?

Our value during construction in 2017 was KFW 55 with ventilation at 0.51 without special precautions. I would say anything below 1.0 is good. Below 0.5 would be passive house.

I find the value bad, would have the errors searched for and now where possible still fixed .... don't let yourself be fobbed off by them, it's like passing the exam with a 4.0...

that is like passing an exam with 4.0...

As long as the quality characteristic is only pass or fail, it really doesn’t matter in reality whether it was passed with 1.0 or 4.0.
As long as the limit value (1.5 is also familiar to me here, without wanting to nail myself to it in the context of current standards) is met, everything is fine. As long as you have not made any special agreements beyond that, I see neither reason nor basis to have your BU make any corrections that are not defects.

I don't understand: the tangible and visible defects are supposed to be fixed during the BlowerDoor test

Obviously that didn't happen, otherwise the value would be different. The BDT was passed, but the value indicates possible defects. We passed twice because I did two tests. @TE: First clarify whether the chimney was sealed.