Humidity headache!

[Giant Flying Wombat]

Hey guys,

Been battling climate from the get go, foolish to start a grow mid spring in Australia in a small tent in a generally hot house, lesson learnt!
Growing in a 2x4 so do not have the luxury of adding robust equipment inside.
Humidity is anywhere between 60%-80% and im week 9 flower! Plants are not in a happy place and theyve been suffering for a while now.
I bought one of these mini dehumidifiers, 700ml total capactiy, 300ml a day, not all that much I do know, but cant fit anything larger in the tent.
External humidity at around 50%.
2 plants getting 4 litres a day each. Usually with 20-25% run off which gets thrown immediately to ensure no standing water.
Against my better judgement I defoliated to try to help, but doesnt seem to of made any difference, humidity still hits 80%.
Got 3 little fans in there, a 6'' exhaust fan on full force (plenty of air movement & exchange), and ac pumping air in to keep temps below 25c.
Im not sure what else I can do thats viable.
Do I need to keep my humidity probe further away from my plants maybe? its right at canopy level with the temp probe.

Any thoughts hugely appreciated!
Cheers
GFW

 

[Giant Flying Wombat]

Couple of pics....
Just moved the sensors. Raised then a little over the canopy. Just fed and tents open so it’s equalised with the outside. Will wait and see what happens overnight

 

[woody]

You running an extraction fan? Any way of turning it up

 

[Giant Flying Wombat]

Yup, 6” Ac infinity exhaust through carbon filter. Running full pelt and moving a fair bit of air through

 

[woody]

Are tent flaps open helping any mate?

 

[Giant Flying Wombat]

theres two intakes, but I keep the vent flaps closed, too much light leak and hard with pest control. I run ducting through two 150cm ports with stockings stretched over for a fine mesh.
My ac is also hooked up to the tent, so I have to be careful on how I vent. If I open the flaps, when the ac turns on it will just push the air out of them and stink the place out.
Its a fine balance which I managed to make work with temps and keeping negative pressure. Now the humidity is the issue, doh.

 

[Filthy_Casual]

Those little ones don't work, I had 2 of them in a larger tent and they soaked up a bunch but maybe moved the RH 1%.

I bought a big one and put it in and that is the only way it worked. What I suggest is get a nice big one put it outside and keep your RH outside the room to 40% or so, then run that AC infinity to get that dry air in.

Other than that, set up some sort of 90 degree angle vent on the top to stop light leaking back in during dark, but let humidity and heat out the top.

GL

 

[Trichome farmer]

seems to me like filthy has the best idea buy a larger dehumidifier and rig it up outside the tent somehow( cardboard ductape and some ducting ) or maybe if you have the space switch up to a 4 x 4 so theres room for the equipment inside im having the same problem myself i run 9 plants in a 4x4 and im going to have to grow one less plant to fit in a bigger dehumidifier

 

[Simplicio]

Greater air flow thru the system should solve your problems.
If you are venting to the outside, there exists a large enough air flow that can make Temp and RH inside the tent come close to conditions immediately outside the tent.
This must be true (but not necessarily practical), because infinite fan speed would guarantee it.
I the exhaust fan is too weak, or if the air resistance of the filter is too much, then you might need to help the fan out by using 1 or more intake fans.

I've always been skeptical of warnings to keep humidity low during flower, because that violates the VPD chart.
I keep mine around 65% and temps around 76 F from seed to harvest, and have never had bud rot.
Maybe I'm lucky, but I don't think you should worry too much.

 

[Giant Flying Wombat]

Hey guys,

thanks for the thoughts.
I’m really not making this any easier, tent location is very awkward in this situation, same problem I had with the Ac. In an ideal world the tent would be in its own room in which I controlled the temperature and humidity of that. In reality I’ve got my tent in the attic which is actually a mezzanine (open to the living room down stairs). The house is long and rather thin, like a giant boat shed, and all the heat accumulates up here. Builders did a doozy not putting in air vents and the insulation must be trash.
Either cooling or dehumidifying the local area is very difficult. I had to screw a flange of sorts to the vent of the Ac to direct it straight into the tent with ducting, I also had to put a hole exactly the right size in the ducting connection to vent some of the air to ensure I would not reach positive pressure in the tent.
I do have a large dehumidifier in my sons room, but that thing heats up! Heat is also my enemy right now. Especially in this attic in Australian summer. I do realise I’m a fool for growing in an attic conversion at the start of Aussie summer!
Putting a 90 degree vent in the top would surely just leak a lot of smell? I must say there is a considerable amount of air coming out of the exhaust. That’s why I’m a little miffed as to why the humidity isn’t being balanced out as the exterior is generally 50%.
sounds like I’m resisting help! Just trying to figure something out that’s viable for my very specific situation!
That’s encouraging Simplicio, hopefully I won’t have rot, but my plants have not been happy. Could be other reasons too, they were over fed, but even after multiple flushes they’ve never really recovered and have only gotten worse.
Thanks again guys