Window U-value - What savings on the long term?

Hi,

I am currently concerned with which U-value I should aim for with the windows in my new build. It only needs to comply with Energy Saving Ordinance 16.

At the moment, I have an offer for a Uw of 0.89.

I am interested, for example, in whether an additional investment in the windows pays off through heating cost savings. On-site advice was rather that if no KfW standard is to be met, the normal version is sufficient.

What do you think?

PS: Wall construction is 17.5 cm aerated concrete WW2, core insulation WLG35 18 cm, 11.5 cm facing brickwork

With the wall, you can even achieve KFW55 (if you also take care of windows and heating).

But everyone has to decide that for themselves.

Intuitively, I would agree with your specialist. Probably, you can't save enough to justify the extra cost. But I couldn't calculate that. You could just do something for your conscience and say..
Yes... Condition not only barely met but exceeded.

Don't focus on U-values when buying windows, but pay attention to the torsional stiffness of the profiles, good fittings, roto or Schüco for example, solidly made seals. Then the window will be draft-free, intact, tight for many years, which saves heating costs; the difference uw 0.92 to 0.88 does not. Karsten

I claim that it does not pay off when viewed in isolation. The heating costs will be low anyway. But: the quality of the material and installation is essential for the windows! You should definitely not save money here!

Aldra windows are manufactured here in the town and have a very good reputation in the region - both among companies and private individuals.

To be honest, we have not paid attention to compliance with KfW 55, as I understood that their loans are not really worthwhile from 18.04 onwards. However, I am happy to be proven wrong.

The current plan is as follows:

KFW 124 - 50k at 1.55% fixed for 10 years

Bank - 150k at 2.18% fixed for 29 years 4 months