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Old 08-24-2015, 05:32 PM #11
RockinRobot
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Originally Posted by mowood3479 View Post
I like to run rooms at 78f and 70%rh and drop down to 60% rh the final week. I haven't seen any rot in a couple years.. with significant airflow rh at 70% shouldn't be a problem. A room with stagnant air and >70%rh could be a problem
I live in Florida and mold is an issue here(not just in plants). Every article I ever read said 60-70% during veg but RH should be below 60% for flower and most prefer 50% for flower. According to the VPD chart, for proper VPD, I would need to keep my room at 64 degrees at 50% RH and 66 at 55%. I already have to run a dehumidifier to keep RH low because AC can't keep up with our 90+% humidity.
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Old 08-24-2015, 06:11 PM #12
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My room runs at 78 degrees Fahrenheit and 64% rh and my plants love it. The key to keeping pm/mold away is a shitload of airflow,if your buds ain't moving you're begging for pm or mold to set in. My circulation fans and intake/exhale fans run 24/7. And I've never had mold/pm. It was a pain in the ass to lightproof but well worth it.
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Old 08-24-2015, 06:21 PM #13
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Midwest that's where my rooms are at as well.

I think mowood is on the right track with proper circulation. I've got nearly 2x a minute air exchange and the flowering plants enjoy the 65% rH.

only mold issues I've had were from flooded pots while we were dialing in the blumats.

i hope I can keep night temps comfy for them when winter sets in.

kowhite makes a good point that 65% rH would not work well in sub 60*F temps.
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Old 08-24-2015, 06:24 PM #14
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I was growing in a cedar closet for a while a couple years back and when the rH was super low in the depths of winter, I'd take my pump sprayer and soak all the walls and ceiling. instantly bumped humidity up 20% and lasted for a couple hours. that plus a little humidifier got me through.
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Old 08-25-2015, 04:41 PM #15
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Agreed heady, mowood, and midwest, I think airflow is key. I'm putting a lot of focus on it while designing my room. In the end I'm sure some may say I've overdone it a bit. But I'm pretty confident that when it's all said and done my girls will love me for putting in the extra effort.

Midwest - Nice...those temp and rH values pretty much line up with what that chart in that article says is ideal (mowood's do too). I'm sometimes skeptical of the validity of some of the info I come across online (or in books for that matter) even if it seems to make perfect sense to me, I like hearing about real life experiences that confirm it.

SpacejunkOG - Again, good to hear real life examples. Even if they're bad experiences. I was wondering what you did to fix this problem to prevent it from happening again?

mowood & midwest - if you guys don't mind a few questions I was curious to know....

How much air are you moving?
Whats you're total air exchange per minute?
How did you setup your intake/exhaust for your room?
What kind of filtration system do you use?


Peace and CBD grease...
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Old 08-27-2015, 03:28 PM #16
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My total air exchange per minute is about 440 CFM. 440 exhaust intake is 400 with four circulation fans to keep every plant in a gentle breeze. Filter I use is 6" phresh filter that's what I use Ina 4 x 4 tent during the summer. Winter time my air intake and exhaust are triple that cause winter time is in a 11x 14 foot bedroom. As far as intake/exhaust setup I just cut holes wherever I need em to exhaust out after going through my filter intake the same just no filter.
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Old 08-28-2015, 04:05 AM #17
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How does VPD change in a sealed environment? What I'd really like to see is the ideal VPD for cannabis in an indoor environment, not a greenhouse. According to all of the charts I've seen, in a sealed room with CO2 and 84 degrees f temp. requires 75-80% RH (at least for veg). Maybe indoor and greenhouse requirements are the same?
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Old 08-28-2015, 08:57 AM #18
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Great info in here.

However, shouldn't growers with these considerations also consider, that (too) high humitidy figures probably will kill/expire carbon scrubbers?
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Old 08-28-2015, 04:22 PM #19
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I shoot for being able to exchange all the air in the room 2x per minute. So for a room 8x8x8 =512cfm.. I'd have two 8" fans (640 cfm each) pulling out into lung room.. (leaves some room for air flow loss to scrubber and any bends in ducting)
I mount my carbon filters to the ceiling so each exhaust port is set up as filter-fan-ducting-outside
Intakes I set up to pull from down low in the lung room to blow across the canopy in the grow room.
Sometimes I run passive intake (no fans)... Sometimes I'll run two 6" 480cfm fans pulling in.. Just depends on temp issues at the time.
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Old 08-28-2015, 04:26 PM #20
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Quote:
Originally Posted by dubberz View Post
Great info in here.

However, shouldn't growers with these considerations also consider, that (too) high humitidy figures probably will kill/expire carbon scrubbers?
Carbon filters lose effectiveness quickly (6 months or so of continuous use).
Personally I just plan to rotate them out every couple crops.
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