Around 2.5m homes had measures under ECO (and GHG, HUG) during this period. Even assuming all these moved into EPC C+, that still leaves over 3m homes. Can assume some change due to MEES and social housing upgrades, but most change is in owner occupied sector

Which suggests either data is wrong (it’s from English Housing Survey - but EPC database shows similar trend), or my pet theory: actually owner occupiers DO insulate their homes?? Or there’s a range of other things going on that i haven’t thought of….