do i rly need a fan, i have a window that i was goin to leave open but set it up so it vetalate but no light gets in, im not sure if this will work, but do i rly need a fan
How ever you do it, you need some way to move air constantly, circulating it past the leaves of your plant to allow breathable space. So Yes, a fan is the most cost effective way to get circulation. If you are asking if you need say, an inline fan to vent air from your grow room or grow box. Opening a door/window once a day and allowing fresh air exchange can be sufficient if you aren't wrestling with temps.