This is my first grow...here is what I have built in my garage: 4x2x4 grow box, 400w hps (approx 1.5 ft from plants), 8in diameter exhaust fan sucking air out, 4in diameter inlet coming from the front of my house which faces the beach(cool dense air), 8in circulating fan inside grow box, 6 plants total (all under 8 inches). My temp range is 60-85, but my humidity ranges from 13%-20%. I have tried wet towels in the box, trays of water, putting plastic domes over plants, misting ( the mist dries within 5 min), hi-med-low-off fan speeds, but no changes in humidity!!!

What am I doing wrong? What do I need to change? I am on a tight budget so a store bought humidifier needs to be my last resort...

you said you tried water in trays, correct? How big of a tray did you use and how much water? If its too little water, I'm sure it wont do much. Keep the water near your intake so that your exhaust isnt throwing all of your newly formed humidity out of the grow area.

Just a though

with an 8" exhaust and only 1 4" intake the air is gonna be whipping through like a wind tunnel and humidity wont have a chance to rise. need air intake atleast the same size as exhaust. 8" out means need min 2 4" intake.

Thank you for your ideas...I will try a larger tray of water. Also, i did see a change in humidity once I restricted the exhaust...I will now make more intake ports and see how that reacts. Thanks again!

Glad to see your problem is coming to a resolution!

So, i re-did the inside of my grow room and I am at 82.2 deg. and 58% RH...here is what I did. The 400w light was as high in the room as it could be with the plants raised up to the light...I created a mini-green house with a frame and clear plastic, its placed at the bottom of the room now with the light dropped down to the plants. I pointed the inside fan up towards the light and restricted the exhuast even more! I opened up a few more intake holes with a fan sucking fresh air in, and placed a number of soaked "sham-wow's" in the mini green house...

Once the plants fill the area up more, will the humidity naturally rise on its own?