Help! High Humidity

I am helping a friend with his legal grow and we are experiencing very high humidity problems in a box, along with what comes with that, powder mold. I have a little experience from many years ago and he has none, just to give you an idea on experience level, ie. we are beginners. This is my first attempt at helping someone grow in a much more humid environment than I am used to. We have tried several things to resolve it so far but nothing is helping. There is only 1 more thing left to do that I think will solve the issue but I want to get a second opinion because my friend doesn't want to play guessing games anymore, he just wants to issue fixed. Humidity has been in the 70-85% range the entire grow. We are now starting week 4 of flowering. A few pictures before I get into what we have done. My main goal of this box was to use the least amount of electricity possible, and we are using just under 300w for the entire box.









So, as expected, as plants grew, humidity has risen from 65% up to 85% at its highest. When it reached 80% I added a small dehumidifier and 4 containers of Damprid. While both methods appeared to be pulling moisture out of the air (dehumidifier fills up every 2-3 days) it wasn't helping. There are 4 125cfm fans pulling air in the bottom of the box and maybe 125cfm going out, so 4x in than out, which we both agree has to be part of what is causing the problems. The box is in a garage. Opening the front and back doors of the garage and closet doors to the point it is a wind tunnel in the garage still doesn't solve the issue. Humidity outside will read 60 while it will still read 70 in the box even with all the doors open and all the fresh air it can handle. We added a vent to the outside and connected the 4 intake fans to the vent so it is getting 100% fresh air on the intake. It exhaust into the garage through a carbon filter. By adding the vent to take in fresh air we were able to drop the humidity from 85% down to 70%, but still can't get much lower than that, and that is way to high as we are fighting tooth and nail daily to fight back mold using milk/water and neem oil. We are keeping it at bay but it is a losing battle if we can't get the humidity down. Other details, 6 plants in 50G container (35G of water) with large air pump and 4 airstones in a 5'x3'x6' box (we realize now there are too many plants for that small of an area and we need to work on our scrog technique). GH nutes + calmag. pH 5.7-6.0, temp 68-72, ppm 620, ec .88. Water used is 0 TDS RO/DI.

So, all that and the only question we have is: Will drilling another hole in the house for an exhaust vent, along with a stronger cfm going out thancoming in solve the humidity issue? Or can we use the current vent as an exhaust (with a 6" booster fan) and intake the air from the garage (so we don't have to drill another 7" hole in the stucco on the house)?

What are the temps? Also, massive amounts of intake is no good. You need more exhaust then intake.

Temps are pretty stable going between 68-72. We have both read that the output air needs to be greater than the intake, and we have that part messed up. By fixing that issue do you think that will fix the humidity issue? Just once I would love to see it get below 50% without having to use a 400w dehumidifier (which goes against the entire goal of the box, low power)

Sounds like ur on the right track. Fix ur exhaust issue and that should fix ur humidity problems.

Along with the above advice, get some oscillating fans in there to move the air around and blow the leaves around.. Leaves sitting on top of other leaves creates puddles of water, and if your air is stagnant, those puddles turn to Mildew and Mold.

Thanks for the responses everyone! We have 2 oscillating fans in the box, one in the back left, one in the front right, and 2 fans on top blowing down on the canopy/LEDs. I think the 'in box' air circulation is sufficient (we are ripping leaves do to the high air flow), it is the exhaust that appears to be causing all the issues and I plan on fixing today. Just came here seeking other peoples opinions on if they also believed that would fix the issue, and it appears that is the consensus, so again, thanks for the responses.

Since you're doing a scrog(from what it looks like) you should thin out the foliage below the screen. Especially now that you're in week 4 of flowering and most of the light is being used by the canopy anyway. This should help air flow and prevent things from getting stagnant in the dense foliage.

Well, sad to say, things didn't improve. I removed the intake from the outside vent, removed 2 intake fans and made them 'in line' fans on the exhaust which goes outside through the 6" vent now. The exhaust feels like a leaf blower on low setting, lots of air coming out now. I have about 250cfm coming into the box with air from the garage, and about 500cfm going out of the box venting outside of the garage (box is about 5'x3'x6'). Humidity has been pretty steady at 70-72% for the past 18 hours, which is pretty much the same as when we had the airflow cfm reversed. I really thought fixing the exhaust would have fixed the issue, but it doesn't appear to have done much to help. Air in the garage is around 50% humidity but the box can't seem to get below 70. 2 of the 4 containers of Damprid were used up within 2 days so I refilled them, and dehumidifier is also working as well as to be expected, but neither seem to lower the humidity in the box.

I am pretty much at a loss now. I will try one more thing today, adding ducting to the intake fans and having them pull air from outside (through the door as a test before resorting to drilling another hole in the house). If that doesn't help I am just about out of ideas (short of the issue being caused by stuffing too much greenery in a small space).

Found the problem and fixed it and now everything seems to be working much better. I had used an insufficient power supply for the inline fans and it died shortly after I left, which is why nothing changed. I swapped out power supplies and made ducting for the intake that goes outside and it seems to have fixed the issue. Getting the inline fans working on the exhaust dropped the humidity from 80 down to 68 in about 15 minutes. Adding the ducting to the intake and pulling in fresh air dropped it down to 62, which is what the humidity is at right now outside, and a little above norm which is 40-50%. Hoping to hear that it drops below 60 by the morning.

Also took Shaggy's recommendation and cleaned up some foliage at the bottom of the plants, way under the canopy. Much better airflow under the canopy from the 2 oscillating fans now.

um bro i see ur temp meter is very close to the w.e medium ur using i had my meter right on the dirt and it would read 70percent but now its hung up near the budsights and it read 40.

I know you said you already fixed the problem , but be carefull with those electric humidity gauges they can be very inacurate

Thanks for the heads up! I have often wondered if the gauge is accurate, to the point I have replaced the battery 3 times and it is only 2 months old. I look online for the humidity reading in my city (there is a weather station 2 blocks away), then take the gauge outside and it seems to always be about 10% higher than what the weather station is reporting.