Draft at the corners of the windows?

Hello everyone,

I bought a 2-year-old house, a prefabricated house in timber frame construction. It was not fully completed by the builders in all details, for example, interior window sills are missing. And here is the following picture, see photos. There is a slight draft through the holes when you hold your hand over them. How do you assess this? In my research, I have already heard everything from - just put the window sill in and it's done to warning leaky, mold preprogrammed... A Blower Door Test was done at acceptance, nl50= 0.63h

Thanks

How do you evaluate it?

Construction defect. Nothing more, nothing less. Faulty window installation is conceivable.

During my research, I already heard everything from - just put the windowsill in and that’s it to beware, leaks, mold preprogrammed…

The latter is not preprogrammed, but conceivable. The former is DIY botch, but it can work. It’s like “repairing” a hole in a pane with chewing gum.

Blower Door Test was done at acceptance, nl50= 0.63h

Someone probably did the test, found the drafty holes, taped them up, and then swore by everything in the world to fix the defect after passing the test...

Construction defect. Nothing more and nothing less. Faulty window installation is conceivable.

The latter is not inevitable, but conceivable. The former is DIY botchery, but it can work. It's like "repairing" a hole in a pane with chewing gum.

Someone probably did the test, found the leaking holes, sealed them with tape, and then swore on everything in the world to fix the defect after passing the test...

Thank you for the answer.
What would be proportionate considering the risks?
To do it and hope it works out, or to open up a can of worms with the developer, slow down the renovation work, etc.?

Open the barrel with the developer

That is the correct and initially only way. Everything else only if it would have to be settled in court in the end.

Clarify the matter with the seller in parallel. In some cases, defects are compensated with a payment (price reduction) and then you would have no claim against the construction company.

What does your purchase contract say about freedom from defects and liability for defects?