ᐅ Colored acrylic-coated windows and KfW 55 energy-efficient house

Hello everyone,

I have a question regarding plastic windows and KfW 55 standard houses. One of the contractors we contacted informed us that combining colored plastic windows (acrylic color coating) with a KfW 55 house is not recommended. They said that due to sunlight exposure, there can sometimes be warping, swelling, bending of the sashes, and even cracking noises. Can anyone confirm this by any chance or have heard of this before? For colored windows, wood-aluminum windows are recommended. The building is a solid construction with Ytong.

Thanks in advance for your feedback!

Rennratte schrieb:

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

How does he imagine it? That UV radiation first checks the energy performance certificate to see what it says and then decides based on the energy saving ordinance / KfW standard whether to deform the frame or leave it as is?

Rennratte schrieb:

that the combination of colored plastic windows (acrylic color coating) and a KfW55 house is not recommended. There can be issues such as deformation, swelling, sagging of sashes, and even crackling noises caused by sunlight exposure. Can anyone confirm this by chance or have they heard of this before?

That's correct. Complete window profiles cannot be made entirely from PVC; there is always a kind of steel reinforcement in the core. These materials have different coefficients of thermal expansion by nature. This effect is negligible with white windows but unfortunately not with the popular anthracite color. In practice, bending problems are more common with aluminum cladding shells than with foil finishes. The cracking noises may be caused by stresses within the window material itself or its interaction with the mounting (or both). I trust acrylic color coatings to be of better quality than foils, so I often recommend Gealan if PVC and color are desired. However, this difference does not resolve the temperature sensitivity issue of the PVC “complete” profile.

Rennratte schrieb:

For colored windows, wood-aluminum windows are recommended.

In my opinion, there are no wood-aluminum windows worth recommending: this combination would inherently be more expensive than pure aluminum, so it wouldn't make sense from a cost-saving standpoint; conversely, reasonably priced products likely hide inferior wood behind the cladding (inferior in the sense that without the protection of the cladding, it would not be suitable for window profiles due to weather resistance).

Making any connection to KfW55 in this context is unfounded.
Since I do not know your house, I cannot give qualified advice on which products, formats, etc., to combine where. Generally, I can only recommend paying close attention to shading on the sunny side—possibly using smaller elements coupled together, choosing large elements like lift-and-slide doors or multi-panel doors with aluminum mullions, or opting for lighter-colored elements on the sunny side. Most mistakes can be avoided by the builder.

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11ant schrieb:

That's right. You can't make complete window profiles entirely from PVC; there is always some kind of steel reinforcement in the core. These materials naturally have different coefficients of thermal expansion. This effect is negligible in white windows but unfortunately not with the popular anthracite color. The bending issue mainly affects aluminum cladding shells in practice rather than laminates. The creaking noise can come from stresses within the window material itself but also from the interaction with its fastening (or both). I trust acrylic color coating to be of higher quality than foil, which is why I often recommend Gealan if you definitely want PVC with color. However, this difference doesn’t solve the temperature sensitivity issue of the overall PVC profile.

Thank you very much for your response!
It seems like almost no new buildings nowadays have windows that aren't anthracite-colored. Does this issue actually occur that frequently in reality? Or why does this topic often receive relatively little attention?

From the start, I was quite skeptical about the explanation related to the KfW 55 standard and anthracite-colored windows. I just thought that conditions in a KfW-certified house might be different (climatically? thermally? or otherwise?) compared to a "standard" house. I will definitely bring this up again with the general contractor and look forward to their explanation.

Rennratte schrieb:

I will definitely bring this up with the general contractor again and am curious to hear their explanation.

Let us laugh along – please share the explanation with us exactly as you get it.

Rennratte schrieb:

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 fixing than others. The stresses in the entire frame become more audible when they can’t be relieved quietly through the working material.

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