Slumlord: Thanks. Yep, I only need ventilation - trying to prevent condensation and moisture build-up. Not worried about heating.
So eliminate, or at least reduce, the moisture in the first place.
This place had an HRV when we bought it, irritating thing would turn on by itself, we found after accusing each other of turning it back on.
We disconnected it which reduced the power bill, stopped the filthy rings around the vents in the ceiling - and the coughing for those with dust allergies - and we have no condensation problems.
This is a standard modern, aluminum window house....but we do have at least 2 windows open a wee bit in Winter - and pretty much all of them in summer.