Prefabricated house, poor sound insulation

For example, you can hear people on the street talking when you hold your ear to the wall.

There is nothing about installation defects ...
The original poster held their ear to the wall and found it to be thin-sounding. Now they are replacing the windows with higher sound insulation class (SSK). If it was due to the wall, it will still be loud afterwards. If it was due to the 32dB window, it will now be quiet(er).

I only know about bricks, and there the manufacturers specify the sound insulation value. Therefore, I can check whether a 70 dB noise is reduced by the specified 40 dB or not?
If not, something is wrong and I have to keep looking.

Hello Theo, there has been a lot of speculation here, very good advice given and causes researched. Of course, you can go looking for clues yourself and replace windows/glass panes. If the house was built in '17, it is still under warranty. Before I experiment following the principle of try and error, I would order an expert. The fee is fixed in advance. And already wrote it, the regulation for this is DIN 4109. If the expert determines it is complied with = bad luck, if not, then you are entitled to rectification, whatever form that may take.

Hello Theo,
there has been a lot of speculation here, very good advice given, and causes researched. Of course, you can go on a detective hunt yourself and replace windows/glass panes. If the house was built in 2017, it is still under warranty. Before I experiment with a try and error approach, I would order an expert opinion. The fee is fixed in advance. And already wrote it straight away, the regulation in this regard is DIN 4109. If the expert finds that this is complied with = bad luck, if not, then you have the right to remediation, whatever form that may take.

He can save his money. DIN 4109 is a joke and if the house doesn’t even comply with it, the OP would have noticed that gravely.

And because he is smart and knows that, he will first replace one window and then consider further steps. That is cheaper than an expert opinion against pointless DIN values that are so low that every cardboard shack meets them.

I understand your collective desire for a logical procedure with an expert opinion. Unfortunately, the builder has been legally obstructed so much that logic doesn’t get you far.

Have you ever read the DIN standard how crooked and bumpy interior plaster is allowed to be?
I don’t need an expert opinion for that; as a builder, I know that unfortunately I am at a disadvantage. Therefore, I save the money for an expert and invest the saved money in repair by another craftsman.

But that has to be decided on a case-by-case basis.

I see it the same way as Snowy. Experts are extremely expensive and often bring nothing. The money is better spent on immediate defect removal. And in this case, you can better look for the defects yourself or at least check the obvious things first. If you don't get anywhere, an expert can still be appointed. By the way, the expert has no significance in court in case of emergency.

Experts are extremely expensive and often bring no benefit.
If you get stuck, you can always order an expert. By the way, in court they have no significance in case of doubt.

I would be interested to know how many expert reports you ordered last year. But in the end, everyone has to know for themselves what they want, whether to tackle the problem at its root or to fiddle around as a layman.

I consider this a pragmatic approach. Order another craftsman, ask him what his ear says from experience. Replacing a glass unit is cheaper than sending in an expert.