New windows, what is the U-value for old buildings from 1978?

Good evening,

we have acquired a new property and are currently working on the topic of windows. We are unsure which U-value is allowed to be installed.

Facts:
- Insulation approx. 5cm house wall
- Energetic quality of the building envelope according to the energy certificate 0.76 w/(m2*k)
- Existing 2-pane glazing and 2 doors single-pane glazing.

Are triple-glazed windows possible?

Thank you very much and best regards

Of course, triple glazing works. The house will then be really airtight (it is also with double glazing). So please heat and ventilate properly. If necessary, install 2cm insulation in the inner reveal during installation.

My problem is rather the fear of thermal bridges in the wrong places and thus mold formation.

You write that the walls will be better than normally good triple-glazed windows (the weak point is the frame, not the glass). And they are also better than double-glazed windows. Or do you have a more precise u-value for the exterior walls that differs from the stated value?

And to ease your fear, I have already told you what to do.

Oh yes, what are these "wrong places" you are talking about? They can only be the reveals.