Yeah, a builder friend told me recently he completes new custom homes and the regs make them so airtight the people move in and get sick. He has to go back and sneak some outside ventilation into the house and then they recover and are fine.
That is because they need to add an AIR TO AIR heat exchanger.
This is standard on any new construction super insulated house. However, they cost thousands. So, it is something they will skimp on if they can. As ALL builders will do.
I used to argue that the building energy codes resulted in “sick” buildings because there was hardly any fresh air ventilation.