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Grow Tent Low Humidity Indoors - Suggestions?

  • by RiffsandSpliffs
  • Jan 14 2012 01:55 AM
  • 16 Replies
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Posted 14 January 2012 - 01:55 AM

Hey guys, thanks for taking the time to inquire!

My problem is humidity. I am consistently running around 30% in the vegetative stage, which is about 35% below where I want to be. I can see signs of humidity stress on the leaves. I even bought a nice humidifier today that runs for 24 hours and it managed to raise the humidity levels in my 4x4x7 tent by 1 percentile.

I have a 4 x 4 x 7ft grow tent indoors. All the air vent have been duct-taped off for an air-tighter seal. I run a Sunblaze T5 4'x8 lamp fluorescent fixture in vegetative, and a 600w HPS (6" air-cooled SunSystems Blazer reflector) during flower.

Currently, temperature is not an issue. I pull in cold winter air for my intake. My intake fan runs at 160cfm. It might run a bit slower, because it's a duct booster fan that I have put a small screen on the intake side to keep dust and bugs out. It runs for 24 hours.

My exhaust fan is a 190cfm inline model with a 4"x12" carbon filter attached to it. I'm assuming it doesn't really pull out 190cfm. The fan is manufactured by MTN Gearsmith. It runs for 24 hours.

What gives? Is there a timer that I can hook up both my intake and exhaust to, that will turn them on for 1 minute, every 5 minutes? Is that even the cause of the low humidity? Or are there other factors I'm not considering. :confused:
Replies (16)

  • This Pain Is An Illusion

  • tothehead
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Posted 14 January 2012 - 02:42 AM

humidity stress on the leaves?

my entire setup, veg & flower, pretty much run 35-40% humidity constantly. i personally dont have problems.

do you have some pictures of your plants?
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Posted 14 January 2012 - 05:26 AM

I thought around 40% humidity was good? My room varies from 48-55 and I try to lower it

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Posted 14 January 2012 - 09:34 AM

I'm pretty sure the standard is 60-70% RH in vegetative and 40-60% during flower.

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Posted 14 January 2012 - 09:36 AM

Ohh ok thank you I wasn't positive

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Posted 14 January 2012 - 04:28 PM

I'm pretty sure the standard is 60-70% RH in vegetative and 40-60% during flower.


Wow, that is begging for mold issues. Keep it under 50% for all stages especially flower. You could creep into 60% tops in veg but 70% is nutty.

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Posted 15 January 2012 - 05:44 AM

Okay, so I'm guessing below 40% is the norm for indoor growers, and I'm comfortable with knowing that.

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Posted 15 January 2012 - 11:26 AM

My humidity is about 64 when lights turn on and about 2 hrs into the lights being on it levels out at about 56 to even 58 sometimes. It's not a problem.

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Posted 17 January 2012 - 02:31 AM

The reason your humidity is so low is because your pulling in cool intake air from outside. Cold air doesnt have the ability to hold moisture, so you get the lower rh. Humidifiers cant compensate as well in low temps either.

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Posted 17 January 2012 - 04:08 AM

veg 40-60 rh. flower 35-50

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Posted 15 December 2014 - 01:40 PM

I've actually been running 25-30% humidity this go around (just to test) in a 2x4x5 tent and see 0 negative affects (other then thirsty plants:)
I use 6" intake and out fans and put a variable speed adjuster on them both.
Want a lower humidity just turn the out going fan a litter higher..



I am so open minded you should only think like me..

  • Steve Tentpackar

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Posted 15 December 2014 - 04:00 PM

I run 30% or lower in veg and flower. Just means they take up more water.
Its just a weed grown in the desert...not a succulent from the rain forest.
Less chance of mold or bud rot.
Increased trich production to protect itself
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Posted 15 December 2014 - 04:49 PM

Hey guys, thanks for taking the time to inquire!

My problem is humidity. I am consistently running around 30% in the vegetative stage, which is about 35% below where I want to be. I can see signs of humidity stress on the leaves. I even bought a nice humidifier today that runs for 24 hours and it managed to raise the humidity levels in my 4x4x7 tent by 1 percentile.

I have a 4 x 4 x 7ft grow tent indoors. All the air vent have been duct-taped off for an air-tighter seal. I run a Sunblaze T5 4'x8 lamp fluorescent fixture in vegetative, and a 600w HPS (6" air-cooled SunSystems Blazer reflector) during flower.

Currently, temperature is not an issue. I pull in cold winter air for my intake. My intake fan runs at 160cfm. It might run a bit slower, because it's a duct booster fan that I have put a small screen on the intake side to keep dust and bugs out. It runs for 24 hours.

My exhaust fan is a 190cfm inline model with a 4"x12" carbon filter attached to it. I'm assuming it doesn't really pull out 190cfm. The fan is manufactured by MTN Gearsmith. It runs for 24 hours.

What gives? Is there a timer that I can hook up both my intake and exhaust to, that will turn them on for 1 minute, every 5 minutes? Is that even the cause of the low humidity? Or are there other factors I'm not considering. :confused:

     Is the fan for the light drawing air from outside and exhausting back outside or into the room? if it goes into the room it will be very dry air and will bring down humidity in the entire room, and eventually the tent.

     You should get a speed controller for the tent exhaust fan, it is exhausting the tent faster than the humidifier can keep up. http://www.ebay.com/...=item1c3e06d9b3  


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Posted 15 December 2014 - 06:02 PM

I'm with greenthumbs21 on the topic of low humidity = increased trich. But, if you need to raise humidity, grab a 5gal pail, or anything that will hold a certain amount of water. Find a way to hang a coat hanger from the ceiling of your grow space, drape one end of a towel over it and use spring clamps to secure it. Hang the towel so it hits the bottom of your container and fill with water. The water will wick up the towel due to capillary action and as the water evaporates, your RH will go up. Not an exact science but cheap and relatively easy to do. If you have a fan, place it in the flow of air. Check the water regularly and fill as needed.

 

I hope this helps,

-PG


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Posted 15 December 2014 - 10:38 PM

Keeping the lower leaves out of the soil (if used) is pretty important with low humidity. Spider mites and a few others might be an issue...but clean and tight is a very successful deterrent..


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Posted 09 April 2015 - 09:31 PM

I have a small tent just started growing its 28×48×60 I think my fan is to powerful for tent its 190 cfm intake haven't hooked it up yet should I or not also have 600watt mh/hps grow light please help

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Posted 09 April 2015 - 11:14 PM

In SOCAL, 30% is downright balmy.

 

I have no issues with low humidity in veg, and I much prefer it in flowering.

 

Where you really have to watch out for high humidity in flowering is during the dark cycle. Plants transpire a lot of water during the dark cycle and that's when humidity can shoot up to ridiculous levels and cause bud rot (especially with higher temps during the dark cycle).



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