desperately need advice on humidity control!

[nightOWL]

I've been researching and understand the desired range of humidity during flowering and how you want to knock it down even further during the last few weeks... my issue is how to accomplish this!

I've got a 4'x4' tent in an attached garage. I live in the pacific northwest and right now my RH in the garage is 75%...

you can see the latest pictures in my grow journal in my signature below, the plants have been doing well, but I haven't given a thought to humidity during veg. I started flowering a few days ago and i'm getting worried. I have a 30pint/day dehumidifier running full time inside the tent, but it doesn't seem to be doing much... i'm still flirting with 75-80% RH.

I've got the garage sealed as best I can, no cars in or out. I have a 600w light with duct work in and out of the tent, a fan attached to that duct work, pulling air past the light. I've done my best to seal the duct work to the light as well as seal the glass around the light. I have a fan in the tent blowing on the plants, but that's it... the tent isn't that freaking big! 4'x'4'x7' = 112 square feet. Is there anything else I can do?

Please, any suggestions would be appreciated!

Thanks in advance!

 

[Cruizer]

I saw a small fan in one of your pictures inside the tent, may be get a larger oscillating fan Need to move the air around in the tent and that will also help lower the humidity and keeping it warm too.

 

[wizgrow]

More air circulation helped me a few percent but sounds like you need a dehumidifier added. When I add mine it adds a little heat but you should be fine in your area. I moved from Wa but don't remember it being that humid......

 

[Fuzzy Duck]

Ye i took a brief look through your journal...

Current extraction fan seems a little low ya more likely want a 6" or 150mm inline fan running 24/7.

Dehumidifiers work on basis of treated air per hour bit like inline fans really at moving air so if in direct competition of each other is the dehumidifier really working at its best ?


I suspect you have a passive vent intake !


I might suggest leaving the dehumidifier in the garage to treat a larger volume of air running 24/7 than have it inside the tent if running a passive intake for better results


Ye i recently moved over to a dehumidifier after suffering with bud rot in flowering with some strains grown in the past, yyou could look into mold resistant strains in the long run ?

Humidity does spike during the lights off period tho, a slight problem.. just look at any good weather forecast to see what RH does during the night time, the same go's for indoor growing on a micro climate scale


I run my own dehumidifier during lights off knowing a spike in RH, whilst in flowering 60% RH plus could prove a problem & no it is not in the tent it self.

 

[nightOWL]

Ye i took a brief look through your journal...

Current extraction fan seems a little low ya more likely want a 6" or 150mm inline fan running 24/7.

Dehumidifiers work on basis of treated air per hour bit like inline fans really at moving air so if in direct competition of each other is the dehumidifier really working at its best ?


I suspect you have a passive vent intake !


I might suggest leaving the dehumidifier in the garage to treat a larger volume of air running 24/7 than have it inside the tent if running a passive intake for better results


Ye i recently moved over to a dehumidifier after suffering with bud rot in flowering with some strains grown in the past, yyou could look into mold resistant strains in the long run ?

Humidity does spike during the lights off period tho, a slight problem.. just look at any good weather forecast to see what RH does during the night time, the same go's for indoor growing on a micro climate scale


I run my own dehumidifier during lights off knowing a spike in RH, whilst in flowering 60% RH plus could prove a problem & no it is not in the tent it self.

Thanks for the post!! So I have a few follow up questions... If i'm facing the tent, on the right side, I have a 6" duct coming in to the tent that seals up to the light. On the other side of the light I have 6" duct leaving the tent that connects to a 6" inline fan that is outside the tent. that fan only runs when the light is on (same timer). Inside the tent I have a little 6" fan that does not oscillate. I placed my 30pint/day dehumidifier inside the tent on continuous setting (i think it's trying to get to 35% on that setting?)

So are you saying that I may be sucking out some of the dehumidified air out through the tent? I'm trying my best to keep the whole duct-light-duct-fan system closed off...but maybe i'm not doing as good of a job as i think?

so if i take my dehumidifier out of the tent and let it work on the garage itself, should I get some sort of inline fan to get air in to the tent? I have a 6" duct in the ceiling of the tent that is unused right now.

 

[Jedthedog]

I run a 6" fan with a speed controller this pulls through a carbon scrubber then a enclosed hood and out of the tent. I regulate the temperature and humidity basically with the speed controller for the fan ..

 

[Fuzzy Duck]

Sound like you are running an air cooled hood.

But have no air exchange going on ?


Some thing sounds odd with the set up ?


By any chance can you post some pic's of the set up as i may need a better idea to what we are dealing with - Photo Gallery Guide - How to Resize, Upload & Post Photos


Some other stuff...

It is better to push air through the air cooled hood than suck it through.

The grow tent air needs to be exchange around 20 times a hour to help provide plenty of fresh air for the plants, it is pretty important.



I work on a passive intake system & active exhaust/out take.

Heat go's up or rise's basic law of nature, so my carbon filter is fitted to the extraction fan placed at the top of tent.

The lower section of the tent has passive vents this is my air intake... so as the extraction fan takes air out of the tent it pulls new fresh in via the passive vents.

That is all in my spare bedroom the dehumidifier sits in the hall way outside of the bedroom treating a larger volume of air, the bedroom door is slightly open acting as 2nd passive form of air intake, i've had the dehumidifier in the same room set at 50% but it switches it self off once it achieves setting some sort of energy saving mode didn't work out to well for RH control tho in the smaller room.

It does have a continous mode of action 40% i think, which i mainly use in flowering with good results lights off Rh stays around 50 to 55% most of the time, lights on 40 to 45%.


How ever house hold RH vs garage RH & seasonal variation summer/winter of RH value due to weather etc does change things slightly between the two areas.


I don't think a sealed environment can really be achieved in a garage & a tent grow... but manilipation of such & a change of tactics can be done !



Some extra banter

Right i done some research on my dehumidifier before i got it... it treats 180 m3 per hour my exhaust fan removes 400 m3 per hour, ya sorry for the metric.

So if i had it in my tent is it really working at its best ?

 

[nightOWL]

FuzzyDuck: Thanks so much for the post and help... i popped out to the local hydro store at lunch before I saw your post and they told me the same thing... I'm in a situation that I don't have to worry about odor so I won't need the filter for the time being, but I do need to get those flaps opened in the bottom, add ductwork and a fan to the top port of the tent to get more air flow going... they also suggested at least a 12" oscillating fan as well... going to get all of that setup tonight and then i'll post some pics! Thanks again for the advice!

 

[Cruizer]

I grew up in the Oregon and know how wet it is over there. Your next grow you should time it where she flowers in the short summer months. Glad you got it worked out. and learned some stuff to help the next guy.

 

[Fuzzy Duck]

It was a pleasure to be of some assistance.

 

[nightOWL]

Just a quick update...

I added a fan and duct work to the top vent of my tent and opened up the bottom vents as fuzzyduck suggested. I took the dehumidifier out of the tent and placed it in the garage that houses the tent. I drop the water out of the dehumidifier twice a day so i won't kick off when i'm not around.

end result: humidity in the tent is down in the mid 50s during lights on, and it does jump a bit to the mid 60s while the lights are off, but I haven't even seen it in the 70s since going with this setup...

thanks for all the suggestions!!


counting down the days to harvest, dry, cure and

 

[wizgrow]

Quick note on dehumidifiers and dumping the water. I often travel for a coupe days and can't be around to dump/drain it (Neither of mine have external hook ups) So i just took the water capture buckets out and jammed a plastic coat hanger in the receptor to engage it to be on..... then put them 12 gallon totes propped up on 2x4's and just let the water drain into those........ I could be gone a week if needed with out having to drain those

 

[Surf420This]

I have the same size tent, and the 6"inline fan wasn't enough. I have been told to get a high velocity inline fan. Once I made the switch, amazing difference. Just my input. good luck man. will be following along

 

[JNew]

nice setup you have. little idea for a product you should try. I work for Eva-Dry and we have a product to check the temp and RH levels from outside of the grow tent. every time you open that door just to check levels on a hygrometer you're going to let more humid air in. this product could be a big help to your efforts to keep your humidity in check. also check out some of our dehumidifiers. they don't put off any excess heat back into your tent like a conventional dehu would. just a suggestion. but here is the item i was referring to. hope everything works out for you.