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What percentage of RH(humidity) should ones grow room(s) be at to avoid mold?

jammie

ganjatologist
Veteran
It's a lack of good air circulation that causes mold. It's important to run a circulating fan and preferably an intake and exhaust fan 24/7. I run my humidity between 60-75%. remember to stop your humidifier with light out or your humidity will go way up. Humidity is relative to tempurature. Remember the old adage- a rolling stoner gathers no moss. It's because of air movement
 

Rabbi

Member
I've got plenty of air movement and I don't use a humidifier as the last thing I need is more humidity. In fact I'm thinking of adding a de-humidifier. That's what brought this question to mind.

So you would say 60-75% is what a guy should be aiming for? Thx for the info man.

I haven't noticed any moldy buds but noticed a bit starting to grow on my walls and see that is a bad sign so figured I better get on it before it becomes a major problem.
 
D

DHF

70% RH through end of stretch , and as low below 50% as possible till end of cycle , but major air exchange twice per minute is your friend unless runnin a sealed room , and.......

In that case keeping ambient room temps within a 10 degree variable between lights on and lights off will help prevent condensation during lights off when RH goes waay up during mid-late bloomage.......

Lack of air circulation "through" the plants are your worst enemy while in swellage mode , so keep the insides cleaned out gradually with all fans with a stem removed after complete end of stretch is over till they`re all gone , and if they still keep poppin out , you have too much N left in your mix , so adjust accordingly.......

Peace....DHF.....:ying:......
 

Rabbi

Member
70% RH through end of stretch , and as low below 50% as possible till end of cycle , but major air exchange twice per minute is your friend unless runnin a sealed room , and.......

In that case keeping ambient room temps within a 10 degree variable between lights on and lights off will help prevent condensation during lights off when RH goes waay up during mid-late bloomage.......

Lack of air circulation "through" the plants are your worst enemy while in swellage mode , so keep the insides cleaned out gradually with all fans with a stem removed after complete end of stretch is over till they`re all gone , and if they still keep poppin out , you have too much N left in your mix , so adjust accordingly.......

Peace....DHF.....:ying:......

I am actually running a sealed room with a 5 ton AC ductless split with 2 heads. I have all my fans turned off during the dark period, is that possibly what my problem is? Should I be leaving them on 24/7?
 

Crusader Rabbit

Active member
Veteran
Your air supply can be an issue also. The last year for me was a botrytis nightmare. I had several crops that were full on fails, eventually lost my mothers also. Turns out that with my grow room pulling new air from under the house, I was bathing my plants in spores. I'd allowed leaves from shrubs along the house to pile up outside and they turned into a fungus colony. Raking this debris away created a thick cloud of airborne spores. My plants never stood a chance with air being pulled through these leaves.

I'd spent a small fortune on antifungals and oxidizers but turns out that dealing with the source of the problem was quite simple ... at least I hope it was.
 

LEDNewbie

Active member
Veteran
I kept my room between 70-75% during veg and first 3 weeks of flower in my sealed room. Then even with my sante Fe classic the lowest I could get my room down during full swell was between 60-65%. Just finished harvesting, no mould anywhere!!! Key is lots of air movement above and below canopy!
 

LEDNewbie

Active member
Veteran
I am actually running a sealed room with a 5 ton AC ductless split with 2 heads. I have all my fans turned off during the dark period, is that possibly what my problem is? Should I be leaving them on 24/7?

Fans have to run 24/7!!!!!!!
 
D

DHF

LED knows the drill....Air movement "above" AND "below the plants , but never ON em so as not to increase trainspiration that fucks with nutrient uptake , and even offset above and below to create a "vortex" of air circulating around the plants as well as above and below em is the way to keep shit from happenin , but.......

In a sealed room the dehuey hasta work overtime with buncha plants transpiring into the ambient air 24/7 and even moreso during lights out , so......point blank........

Dial environment first and foremost , and worry bout everything else secondary.......and Crusader......Man I`m so sorry.........

I should`ve posted this shit yrs ago since it was the absolute lifeline to fresh air intake into my lung areas and have constant turnover into my flip rooms......

I ran in basements with a "crawlspace" like you`re talkin about and had the same issues in the Hell of the dirty south with all manners of nasty ass airborn pathogens livin large on untended ornamentals/landscaping around the houses , and it`s easy to maintain with a DIY "HEPA" filter in front of the active intake for the grow areas......

Had mine wrapped with "pantyhose" over the outsides of the intake filters , and with major air exchange twice per minute I never saw mold or mildew issues in many many yrs of indoor croppin.......Anyways.....

Good luck....DHF.....:ying:......
 

jammie

ganjatologist
Veteran
here's a good article. it also explains vapor pressure deficithttp://autogrow.com/index.php?option=com_content&view=article&id=31&Itemid=165:
 
D

DHF

its temps you need to worry about. Ive grown in 90%+ humidity rooms with temps around 80 and have never seen mold once in 15 years.
Well CB.....Tell us about your environmental control in place that allows you to grow with 80 degree temps and 90% RH during lights on and off......

I`m just sayin......I live in the Hell of the deep dirty south with RH as you talk about , but without SERIOUS attention to airflow and filtration into and out of each of my fliprooms , airborn pathogen possibilities were inherent from constant perfect conditions for em to form , grow , and proliferate.......so.....that said......

Gotta respectfully disagree about temps bein the only factor to be watched out for concerning airborn pathogen formation in ANY grow area , cuz NOTHIN could be further from the truth IME , but I digress......

Please come back with your thinking behind this theory.....

Peace....DHF......:ying:.....
 
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Perpetual Nooch

Active member
I run sealed room with co2, air conditioner, and dehumidifier. I keep RH at around 50% throughout the life of the plant. I haven't noticed any detrimental effect on growth in veg or flower. And never had mold.

To simulate late fall, I like to drop the temperature at night during the flower stage, so I need to run the dehumidifier or else condensation forms. The AC runs 24/7, as do all circulation fans in the room. The AC helps with dehumidifying during lights on.
 
Well CB.....Tell us about your environmental control in place that allows you to grow with 80 degree temps and 90% RH during lights on and off......

I`m just sayin......I live in the Hell of the deep dirty south with RH as you talk about , but without SERIOUS attention to airflow and filtration into and out of each of my fliprooms , airborn pathogen possibilities were inherent from constant perfect conditions for em to form , grow , and proliferate.......so.....that said......

Gotta respectfully disagree about temps bein the only factor to be watched out for concerning airborn pathogen formation in ANY grow area , cuz NOTHIN could be further from the truth IME , but I digress......

Please come back with your thinking behind this theory.....

Peace....DHF......:ying:.....

sup DHF! Freedom....13 here(member of krustys Freedom Crew from back on overgrow).

Of course you need airflow. That's a given. You don't need to worry about high humidity if your temps are in check. Grew in FL for 12 years and never once worried about humidity. Couple fans and a cracked window...FTW!:woohoo:
 
and I grew with a dirty ass, muck filled, wasted dump of a swamp less than 50ft from my back door...no filters, nothing. Only pest I ever had was white flies...till I got to Colorado that is. lol
 

SunGrown

Member
you are gonna get all kinds of answers to this, and to be fair they are probably all somewhat correct....many more ways to do many things than just one...

that being said, I agree that temp and air flow matter more than humidity, however until you have personally been able to play with enough test rooms on your own, I advise mostly to keep your humidity below 50% in flower, especially last few weeks...

I have ran rooms at 60% rh and temps as high as 95 in veg with very good results, however if you want to be safe set a dehuey to 45-55% thru your whole grow with your ac set to 80 degrees f and many good air circulations and I think you will be happy

and get on the mold you already see in your room, if you dont you may regret it. make a good bleach spray(or whatever you are comfortable with that works) and get on it, and stay on it thru the end of this grow at least, otherwise it can get into your rooms framework and wreak havoc where you cant see it

hope this helps
 
D

DHF

CB.....Temps like that cause crazy ass RH during lights off , so I don`t know HOW you controlled your environment , and ESPECIALLY if you lived lower in Hell than I do.....but.....

Your blanket statement bout "temps" bein the ONLY thing ta worry about was just wrong , and since you`ve been around as long as yas have , I`d think youd`ve done a better job of explainin said statement , but hey......

I meant no disrespect , and Sungrown is indeed correct that there`s many ways ta skin a mule , but guaranteed.....There`s only 2 ways ta run a successful dialed setup on a consistent basis , and it`s either with a sealed room with all the bells and whistles with CO2 supplements AND all the a/c`s and dehuey`s it takes to keep said sealed area intact and producing with perfect conditions , or......

Air exchange twice per minute with a/c`s and dehuey`s on standby if temps fluctuate within a 10 degree variable during lights on and lights off when RH spikes and goes through the roof from elevated temps if not handled , with either equipment or room air extraction goin on is the other way.....not many other ways work.....consistently that is IME.....anyways........

Just keepin it real , and tryin ta help from doin this shit right for longer than I care to remember.....Doin it wrong and getting away with it`s not the wayta help and teach folks that the wrong way is ok.......My 2 cents from all those yrs.....

Peace....DHF......:ying:......
 
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