ᐅ Timber frame prefab house: Exterior finish/coloring of the south-facing wall

Hello everyone,

we are currently facing the decision to purchase a prefabricated house with a timber frame construction.

Here are some basic details – please let me know if anything is missing:
- Built in 2001
- End terrace house
- Vapor permeable wall structure (outside to inside): 7mm mineral plaster, 60mm wood fiber board, 160mm timber studs / mineral insulation, 15mm OSB board, 12.5mm gypsum board
I don’t have more detailed information about the materials used yet. The U-value according to the building description is 0.17 W/(m² K).
- Partial wall heating installed (I’m not sure if this is relevant).

I noticed the “pattern” on the exterior wall (south side) that seems to roughly indicate the positions of the timber studs and so on. I think the attached pictures show the light/dark differences best (circular lighter spots). So far, my online research only brought up the topic of “dowel fastening” of the exterior insulation.

My specific questions are:
- What causes this pattern?
- Are thermal bridges the reason?
- Is this a construction defect?
- What impact does this have on the building fabric?
- Is it likely that the building fabric has already been damaged or will be damaged in the future?

Thank you very much!

Best regards,
mawoc

PS: I understand that a remote diagnosis is always difficult. I will probably hire an expert as well. Nevertheless, opinions and experiences on this topic would be very helpful.

I assume that there are small, localized, linear thermal bridges at these points. This causes the facade to be slightly warmer here than the rest, so moisture from dew, etc., evaporates more quickly, resulting in fewer algae compared to the rest of the facade.

This is not a problem; it only represents a cosmetic defect.

Best regards