I haven't been ventilating at all and I've been getting fair yields,enough for myself to smoke and enough to give to my nephews too.I thought ventilation was only for the really stinky cannabis plants.I do have a fan running in the room just to keep the air circulating.Of the 3 strains that I've grown (Northern Lights,Blue Mystic and Hawaiian Gold) only the NL had a smell while it was flowering and it didn't smell bad at all,rather a sweet smell is the best I could describe it.I have 2 NL's in the 5'th week of flowering and so far I can't smell anything from them at all.
I do have a dryer vent tubing going through the room so I could tap into it and vent that way but the gas meter is only 5 feet away so that wouldn't be a good idea.