Corners of the new windows are very dirty or scratched

Whether severe or not: the edges are poorly processed and dirty, do not have the usual texture, and are therefore defective in the legal sense. If this were just a minor issue, your supplier could fix it quickly, and I would not accept anything else. What’s next? Split interior window sills with notches and scratches?

When it comes to windows, certain defects must be accepted - just google it. I had to be educated otherwise by my window installer as well. Among other things, we had inclusions of particles (lint), which do not constitute a defect. Also, think about this: a window is a functional item. Grundstück. I also believe that flawless goods should be delivered. For the window installer, replacement would be a total loss, as the profit on windows is extremely low. Therefore, address the issue, listen to what the window installer says, and if necessary, repair and renegotiate (price reduction).

We had, among other things, inclusions of particles (lint), which however do not constitute a defect.

Oh really, and what then?

Also think about this: A window is a consumer good.

No, it is an investment good, installed in room-enclosing surfaces, and significantly influencing the value of the entire property.

because the profit on windows is very low.

The existence of plastic windows is generally only owed to the popularity of penny-pinching in the wrong place. But at least that keeps the price-hunting junkies away from aluminum window manufacturers. Cheers to that.

Certain defects are to be accepted when it comes to windows

No matter what I buy, defects are not to be accepted, otherwise they wouldn’t be defects but the normal condition.

Also think about this: a window is a utility item.

So a scratched and dented car would be fine for you when you pick up your brand new Mercedes from the dealer?

For the window manufacturer, replacement would be a total loss, as the profit on windows is extremely low.

That is then a problem of the window manufacturer and not the customer's problem. Whoever does shoddy work must also take responsibility for it.

We also had a damaged window. There was a tiny chip in the glass in an invisible spot. The window was replaced without discussion.

I would never accept these ugly corners.

is absolutely incomprehensible to me as well - our window installer would be ashamed to install something like that and say: that's how it is, it just needs to be cleaned. And to expect me to do that... *shaking my head