Strong smell when turning down the underfloor heating

Would say based on the components that it could be a used paint or adhesive.

Good day, are there any new insights on what the problem is/was?

Hello, I am attaching what the expert said about it. It definitely does not come from the floor. The smell had completely disappeared for a long time; it only started again with the onset of below-zero temperatures, snow, and wind in combination. The construction company has shown no reaction to the expert report and the complaint about defects (including further defects). Even a lawyer has not been able to help us so far.

I am not a lawyer and may be wrong with the following statement, but the following strategy could help:

1. Set a deadline for rectification. (You have probably done this and the deadline has passed)
2. Announce that the correction of the construction defects will be commissioned to a third company on "date" if there is no positive response.
3. Hire a company, fix the damage, and pay yourself (possibly have it paid by insurance).
4. Send the invoice to the developer and enforce the claim. (They will react and object; if not, you are lucky.)
5. Issue a payment order if no timely objection is filed and then enforce.

Write off the costs in your mind as "bad luck" and be glad if you get something back. This is always better than having to sleep in a stinking room.

Depending on the developer's situation, it can also be a tool to announce in a conversation that you will file for insolvency for the company. If the company is in a good position, you will be laughed at. If the company is in a difficult position, there will be a very quick concession. This tool was successful for me once; once I was completely rightly laughed at.