Colored acrylic color windows and KfW 55 house

Hello everyone,

I have a question regarding plastic windows and KFW 55 house. One of the contractors we contacted told us that the combination of colored plastic windows (Acrylcolor coating) and KfW55 house is not recommended. There can be deformation, swelling, bending of sashes, and also cracking noises due to sunlight exposure. Can anyone confirm this by chance or have you heard about it before? For colored windows, wood-aluminum windows are recommended. The construction is solid with Ytong.

Thanks in advance for your feedback!

colored plastic windows (acrylic color coating) and KfW55 house are not recommended

How does he imagine that? That the UV radiation first looks into the energy certificate to see what is written there and then decides according to the Energy Saving Ordinance/KfW xx criterion whether to deform the profile or leave it intact?

that the combination of colored plastic windows (Acrylcolor coating) and KfW55 house is not advisable. There would be, in some cases, deformations, swelling, bending of sashes, and also cracking noises caused by sunlight. Can anyone happen to confirm this or have heard about it before?

That's how it is. You cannot make complete window profiles entirely from PVC; at the core, there is always a kind of steel tube. That already has different coefficients of expansion anyway. The effect remains negligible for white windows, but unfortunately not for the popular anthracite ones. The bending problem in practice rather concerns aluminum cladding shells than foils. The cracking can come from stresses in the window material but also from its interaction with its mounting (or both). I trust the quality of Acrylcolor coating more than foil, so I gladly recommend Gealan if it absolutely has to be PVC and color. However, this difference does not solve the temperature sensitivity problem of the PVC "overall" profile.

For colored windows, wood-aluminum windows are recommended.

From my point of view, there are no recommendable wood-aluminum windows: in principle, this combination would be more expensive than pure aluminum, so it wouldn't make sense for saving costs; conversely, in my opinion, delicious prices can only result from hiding inferior wood behind the cladding (inferior in the sense that without protection from the cladding, it would not be suitable for window profiles in terms of weather resistance). Making a connection to KfW55 in this context is nonsense. Your house is unknown to me – therefore, no qualified advice can be given about which products, formats, etc., to mix where. Generally, I can at most recommend this: to pay appropriate attention to shading on the sunny side, possibly couple smaller elements, use large elements like lift-slide doors or multi-sash doors with mullions made of aluminum, or choose lighter elements on the sunny side. Most mistakes can be avoided by the builder.

That's how it is. You can't make complete window profiles entirely from PVC; there is always some kind of steel tube in the core. This already results in different coefficients of expansion. The effect remains negligible with white windows, but unfortunately not with the popular anthracite ones. The bending issue actually concerns aluminum cladding shells rather than foils in practice. The cracking can come from stresses in the window material, but also from its interaction with its mounting (or both). I trust acrylic color coatings more in terms of quality than foils, which is why I gladly recommend Gealan if it really has to be PVC and color. However, this difference does not solve the temperature sensitivity problem of the overall PVC profile.

Thank you very much for your answer!
It feels like there are hardly any new buildings anymore that don't have anthracite-colored windows. Does this issue really occur that often in reality? Or why is this topic not given much attention?

However, I was also very skeptical right from the start regarding the explanation involving KfW 55 and anthracite-colored windows. I just thought that maybe in a KfW house it could be different (climatically? thermally? or something else?) than in a "normal" house. I will definitely bring this up with the general contractor again and am curious about the explanation.

I will definitely bring it up with the general contractor again and am curious about the explanation.

Let us laugh along - please tell us the explanation exactly as it is

Does this issue really occur that often in reality?

Yes. But there are shading effects, and some windows can allow a bit more movement in their mounting than others. The stresses in the entire profile become more audible when they cannot peacefully dissipate in the working material.