Yes, its all well and good looking at things like a Passivhaus for a new build, but in places like the UK there are very few opportunities for new builds, given homes have historically been built to last for decades or centuries rather than be torn down and rebuilt every few years. As a result, 76% of UK housing stock is more than 40 years old and 20% is more than 100 years old[0]. Even after the mass destruction of housing during the Second World War, some of the prefabs (built quickly and only supposed to last 10 years[1]) are still in use over 70 years later (in some cases ironically now listed buildings[2]).

[0] https://www.designingbuildings.co.uk/wiki/English_housing_st...

[1] https://en.wikipedia.org/wiki/Prefabs_in_the_United_Kingdom

[2] https://www.theguardian.com/society/2009/mar/17/historic-pre...