Fraud by general contractor? Deadlines missed

If you immediately accuse me of fraud, I won’t respond anymore.

The windows are described in the contract as 0.9. That can be debated.

I did not accuse him of that; he simply rejected my complaints.

Our last conversation was that the underfloor heating, if I had inquired, would have been free of charge in the

Point 8 of the construction description mentions terraced middle houses, which I interpret as a hint at a developer project and that the general contractor may accordingly not even be your general contractor, but that of your developer?

At least this acknowledges you as a legitimate claimant against him. You should have read his rejection as a "declaration of war"—that is, as an urgent indication to respond immediately through a fully qualified lawyer. Whether this would be your own lawyer or one from a consumer protection association is secondary. That lawyer would have immediately pointed out to him that his hallucination of the humorous warranty condition...

... I would say is "not covered by the building code" ;-)

So would it make sense to go to the consumer protection center?

he simply rejected my complaints.

By email? A notice of defects requires a form because it initiates a process that must be traceable and admissible in court. That means: in writing with a deadline, etc. I have never heard, for example, that roof windows are triple-glazed. One or two should be compensated by the rest of the façade planning, right?!

Hello, off to the specialist lawyer. Whoever builds must also accept the risk and create reserves.

I have never heard, for example, that roof windows are triple-glazed. One or two are supposed to be compensated by the rest of the facade planning, right?!

Due to KFW40, we are also getting triple-glazed roof windows. So, this is not unusual now.

Brief follow-up for clarification.

So you received a building description for the roof windows that does not make any statements about the glazing. You bought a house with an energy efficiency level XY – presumably also included somewhere in the contract or the building description.

In addition, you received an energy certificate/calculation that was based on triple-glazed windows.

How can one deduce from this that you have a claim to triple glazing?
Did the house receive roof windows Velux GGL?
Does the house meet the promised energy efficiency level with the actually installed glass?
The company admits errors in the calculation and delivers a new and correct calculation matching the installed materials.

I am just a layperson, but how is a judge ever supposed to follow your claim to better glass? What is the basis – a calculation that the company itself has already admitted to be wrong?
The company made a mistake (calculation wrong) and corrected it. The delivered product (windows and energy efficiency level) corresponds to the contract. Issue closed.

Points 2 + 3 are sent as registered mail (with return receipt) setting a deadline. Afterwards, a brief letter from a lawyer – costs €25 (no idea of the exact price). Then further legal involvement.