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.
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.