Is a house connection room under the house useful?

It is all so deceitful. You are right. Polystyrene is produced, glue, plaster powder, paint, these are transported back and forth, applied to house walls, with the result that two identical houses, one with [WDVS KFW 55] and a second one next to it in the original condition, consume only minimally different amounts of gas, can be found in the ZDF Mediathek as a film experiment. And this is how we save CO2.....

Polystyrene is produced there, glue, plaster powder, paint, all of which is transported back and forth, applied to house walls, resulting in two identical houses, one with ETICS KfW 55 and a second next to it in original condition consuming only minimally different amounts of gas, can be found as a film experiment in the ZDF media library. And that’s how we save CO2.....

So first of all, I would be interested in the ZDF contribution, or at least the underlying conditions, but unfortunately I can’t find it? Secondly: WHICH insulation you put on your wall is up to you. It can be polystyrene, but it doesn’t have to be. And that ETICS is controversial overall (especially regarding dismantling and disposal) is no secret, but ETICS is also not the only option for energetic renovation of old buildings.. And you (or rather the ZDF contribution) really want to claim that a completely unrenovated old building energetically (example 60s, 24cm brick wall, air gap, 11.5cm facing bricks) compared to a renovated house (24cm brick wall, 180mm insulation, plaster) brings no energy savings? Or are you comparing a house with low insulation standard (80s) to a better one? In that case I actually only see savings to a small extent. But meanwhile we have fully drifted off-topic here, maybe the discussion should be continued elsewhere if desired.

Nonsens thermal insulation (hr, "defacto", from 28.02.2016)
Available on YouTube.

Okay.. I have now watched the comments below for quite a long time, it's very entertaining. But the essence of the video is just that thermal insulation makes sense, but only in moderation. That the first 10cm bring more benefit than the 11th-25th cm should also be clear to anyone with some basic understanding of physics.

The first 10-15cm can be done with a porous stone, like the one Ytong produces. The whole North does it that way. That's all you need. K.

it should be clear to anyone with a basic understanding of physics.

The Federal Chancellor has been out of the physics business for too long, and most other politicians were never in it to begin with. The intersection of intelligence and politics is approximately zero (including VAT).