We are literally talking about whether it is practically possible for a major renovation to a lifelong dream home. If they are in love with an old poorly built and insulated home in a very cold area then yes, in a few decades when this do this they will have to have it insulated to at least modern standards and of doing so it’s likely worth it to go to far better, but that is a very long way from your position that no one could even think about it being feasible for anyone in a few decades.
Can I be sure what will happen decades from now? No, but I can say for sure that at the moment, if you want to add insulation to an existing older structure, and not do a complete rebuild, you end up with a structure which isn’t anywhere near as well insulated as a newly-built structure designed for efficiency.
We are literally talking about whether it is practically possible for a major renovation to a lifelong dream home. If they are in love with an old poorly built and insulated home in a very cold area then yes, in a few decades when this do this they will have to have it insulated to at least modern standards and of doing so it’s likely worth it to go to far better, but that is a very long way from your position that no one could even think about it being feasible for anyone in a few decades.
Can I be sure what will happen decades from now? No, but I can say for sure that at the moment, if you want to add insulation to an existing older structure, and not do a complete rebuild, you end up with a structure which isn’t anywhere near as well insulated as a newly-built structure designed for efficiency.
Again, where are you getting the idea that the original commenter has to be talking about being set on a old, poorly insulated home?
That’s pretty much what most retrofits in the US look like.