Heheh, actually, no.
Over the years, I've seen a lot of McGuyver setups along with the commercial ones on the 'zon, but I've always had to vent, so I never pursued it. But even with insulation, I still have to heat the room at night in the winter, so I've been musing about how to take advantage of that. I tried shutting off the fan but the room overheated within an hour, so I still have to vent heat when the lights are on but not constantly. But when I have to run the fan, the room flushes out heat
and the humidity which is my biggest issue in winter - no moist air anywhere. And when I was thinking about stale air, I was also thinking about CO2. But if I have to run a fan for a few minutes every half hour, I can't keep a CO2-rich atmosphere anyway. I could do it at night, but not after lights-on.
It's annoying.
But then I remember that I'm a hobbyist, and I try to get a better grip. Y'know?