Prefab house from the 70s: only 13 cm wall thickness?!

Approximately 15 years after the new construction, the roof was expanded. During this process, additional insulation was added and the heating was switched from oil to gas, possibly due to the oil crisis in between?! The roof or the tiles could also be older than 30 years.

According to the owner, the windows have already been replaced and additional insulation was added.

"collapse" won't happen anytime soon. If the roof still looks good from the outside, meaning no loose or broken tiles are visible and the growth of lichens/moss is limited, I wouldn't worry much.

For the 30-year-old gas boiler, you should already budget 6-8k for a new one. Or rather, I would replace it right away but recommend at least planning for it.

When were the windows renewed? Before 1994? You can find it engraved on the spacer between the glass panes. There is always a date and usually a type description. If before 1990 definitely replace, after 1994 leave it. In between... send a picture of the window and engraving.

Regarding the exterior wall: a folding rule with metric scaling aka measuring stick is your best friend here. Just measure it. Insulation was added? When? How thick? Usually, it is not worth changing anything then, because the U-value is usually 0.5 or lower. So all good.

Edit: Just saw that additional insulation was added during the roof conversion as well. So mid-80s. Probably only 4-6 cm, but it doesn't change the matter: energy standard is fine, don't change anything if everything looks intact.

I started a post about formaldehyde houses, that is prefabricated houses from the 70s, here about a year ago... The thing is that the houses partly have no value anymore because they are toxic

When were the windows renewed? Before 1994? You can find it engraved in the spacer between the glass panes. There is always a date somewhere and usually a type description. If before 1990 definitely replace, after 1994 leave as is. In between ... post a picture of the window and engraving.

Enlighten me: what exactly is the deal with these window construction years?

About a year ago I started a thread here about formaldehyde houses, i.e. prefab houses from the 70s... [Link]

That's kind of you, you save me the search:

Prefab builders at least back then only baked according to a single recipe. In that respect the connection "same construction year, same stuff" is more tightly linked. Although is of course right, 1) that freely sold pollutants were also quite popular for retrofitting and 2) Okal Haus would have had to become notoriously known due to its market share if they had profiled themselves as particularly active pollution emitters. And as you also correctly note, pollutant contamination often only becomes evident through forced release.

A house of the same age from the same manufacturer can therefore quite possibly contain only more peacefully resting pollutants, emit them less, and also be inhabited by less sensitive people (or they become ill from it but are not aware of this connection).

"collapse" won't happen anytime soon.
...
Okay from the energy standard, don't change anything if everything looks intact.

Ok, thank you very much for your explanations.

Indeed, only the pollutant load still seems to be a problem. I have seen that measuring devices for formaldehyde can be bought online. Maybe there are also some for PCP.