Robert Gammon wrote:

Some Canadian houses are extremely airitght, and very healthy.

Yes, very airtight, with controlled, heat exchanged ventilation HRV,
with ERVs recommended.

HRVs are not required by law in every part of Canada. Some of those
airtight houses just have exhaust fans, eg R2000 houses in Ontario.
Exhaust fans waste more energy than HRVs and ERVs, but the amount of
energy isn't large, and it may not matter in a solar-heated house :-)

OTOH, the legal requirement for HRVs on Minnesota's air-leaky houses
seems to be a successful lobbying effort and a serious waste of money.

Nick