Mtmtcanswered grow question 2 years ago A humidifier would be a good idea if you’re under 30% humidity. I have an ultrasonic 9lt humidifier in my 2x4. hooked up with an inbird humidity controller so I can set the humidity depending on the stage of the plants. In my case since I live in a humid environment I have also have a dehumidifier also plugged in my inkbird humidity controller