RE: 15 million homes need energy efficiency upgrades18 Feb 2022 11:29
EnerPHit, which is the Retrofitting Standards of existing homes. It's still the Passivhaus Standard, classified as EnerPHit.
It is severe yes, the level of work is pretty mind blowing. Easy enough for a new build, a nightmare for a 1960's ex-Council home..... Specialist everything, so costs a pretty penny sadly, but worth it if you are looking long term.