Greenhouse: ventilation vs temperature extremes, 1 by Gypsi

Gypsi wrote:
Well it was 40 here last night. When I want to heat up the greenhouse I throw a load of laundry in the dryer, my vent runs out there, and the greenhouse is cozy and warm now, with water on every exterior surface due to the outdoor temperature being cooler.

While this is not ventilation it does dry the air in the greenhouse until the temps come up enough to match. I have a fan I can put out there but my plants are just thriving. Please realize we have a drought and our outdoor humidity is much lower than it was a few years ago. I don't see any fungus or damping off, I did see one fly.

I do not want to vent all that lovely and hard earned humidity to the outdoors. Suggestions?