Citation needed. This number is absurd.
So, around 200 million or so households. Each household (even if it's an apartment) needs both external and internal insulation improved.
Same goes for things like stores, factories, schools, government buildings, and all other non-residential buildings.
Most buildings are built before new energy standards (https://ec.europa.eu/energy/eu-buildings-factsheets_en). In some countries (esp. the Eadtern block) you probably need to teardown old buildings because you can't just simply insulate them (https://news.ycombinator.com/item?id=32202169)
I'd say "100 years" is a conservative estimation
And most of the buildings that instead have a lifespan beyond 2122 are historical buildings built with very thick walls and they don't need insulation work beyond replacing windows.
There are many statistics on building lifecycle that you can easily find on the Internet.
So such estimation is really not grounded in reality.
We need a quote on that. And no, "bulidings last on average 100 years without doing anything to them" is not it.
"Replaced with better buildings" inevitably means "displacing large swaths of population". Because you can't just wave a magic wand and replace houses. For the past 4 years I've lived in a district built in th 60s. So, 60 years ago. If you're telling me that those dozens of building with hundreds of people living in them will be just up and replaced, you're delusional.
