ᐅ Window U-Value – What Are the Long-Term Cost Savings?

Hello,

I am currently considering which U-value to aim for with the windows in my new build. I only need to comply with Energy Saving Regulation 16.

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

I am interested in whether investing more in the windows would pay off through heating cost savings. On-site advice suggested that if the KfW standard is not required, a standard option is sufficient.

What do you think?

PS: Wall construction is 17.5 cm (7 inches) aerated concrete WW2, 18 cm (7 inches) core insulation with WLG35, 11.5 cm (4.5 inches) facing brickwork

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

But that is something everyone has to decide for themselves.

My gut feeling is that I would agree with your expert. Probably, you can’t save enough to justify the additional cost. However, I couldn’t calculate that. You might just do it for your peace of mind and say...
Yes... the requirement is not only barely met but exceeded.

Don’t focus solely on U-values when buying windows; instead, pay attention to the torsional rigidity of the frames, quality hardware—such as roto or Schüco, for example—and well-executed seals. This ensures the window remains draft-free, intact, and airtight for many years, which saves heating costs. The difference between a U-value of 0.92 and 0.88 does not. Karsten

I believe it is not cost-effective when considered in isolation. Heating costs will be low anyway.
However, the quality of the materials and installation is essential for the windows! This is definitely not the place to cut corners!

Aldra windows will be used. They are manufactured locally here and have a very good reputation in this region—both among companies and private individuals.

To be honest, we did not pay much attention to meeting KfW 55 standards, as I understood that their loans are not really worthwhile after April 18th. However, I am open to being corrected.

The current plan is as follows:

KfW 124 – 50,000 euros at 1.55% fixed for 10 years

Bank – 150,000 euros at 2.18% fixed for 29 years and 4 months