That's the older way of doing insulation. Here in Germany houses from around 60 years ago are likely to feature the same.
In the UK we had a bit of a double glazing boom in the late 70s, highlighted well in the TV show "White Gold"
This generic PVC stuff became so common place i'd never seen anything else and just assumed the rest of the world was the same.
That's the older way of doing insulation. Here in Germany houses from around 60 years ago are likely to feature the same.