Slightly unrelated, I have a friend who moved to the US from Mexico and was asking me about potentially buying a house. He started looking on Zillow with me and his reaction to houses build in the 1950s OMG how can it be that houses are that old and my reaction was wow that's pretty much a brand new house. He was blown away that a huge percentage of houses on the market are from the early 1900s and even late 1800s where we live.

It's true that good insulation and sufficiently sized radiators are important. But it's not like those things can't be upgraded in existing houses. In fact, if we're talking about energy efficiency then insulating houses should likely be the first action taken.