"Diminishing returns" for what?

PH is an extremely worthy initiative, but I can't help think it's ripe for a bit of disruption. The whole certification process adds needless cost to a build/retrofit and doesn't help with the perception of high performance homes being expensive.

There's no real reason PH has to be more expensive than anything else. Just that volume housebuilders won't be able to pay minimum wages to people they find on the street any more...