Aqueminianswered grow question 3 years ago Just a heads up, my Autoflowers have no problem growing in 35% - 65%. I started them in 35% humidity no problem. My humidity only climbed up as they got bigger. Now I struggle to keep it below 45%. Just saying, but if you really want to buy one, I'd say built in is better. The cheap ones are garbage for large spaces. For a small space 3x3 or smaller, maybe even a 4x4 a cheap one will do.