Is 20% humidity bad??

I have a AG Veggie with Hood light and 6 100w CFL in a 4 x 4 x 6 high mylar lined grow tent.

I have added a 4 in vent fan and duct tube out of the top. CLosed all other holes in tent except one from the bottom. Im letting suction brinin fresh air.

I have test run this with the lights on ( for 4 hours) and NO WATER the the temp was a steady 85 and 20% humidity.

I had stem issues and the humidity was 30-45%.

I added water and Im seeing if the humidity goes up.

I suspect my issues in the past were due to stem rot from old from having no air circulation except for when I had the tent door open. Now with the duct I have steady air.

My question: Is 20% humidity a bad environment for life in the AG?

I checked it 4 hours later with the water in the rez and it is still 85 degrees and 20% humidity.

This seems like it may solve my issue of everything dying because it got stem rot, potentially from no air being circulated.

The fan i used was a 4 in lin line 80 cfm. That is about the dimension of the tent.

Should I add an intake fan or let the suction handle it?

I think you'll be okay with 20% humidity. My humidity stays between 25-30%, and my plants are fine. But more air circulation and ventilation is always a good thing. Good luck with your grow!

My plants from my 2nd grow got stunted really bad from temps in the mid to high 80's coupled with 20%ish humidity. It shocked them terribly bad and I went from a 3lb harvest on my first grow to 1 lb on this last one. Do Not be passive about that. Do what you can to either lower your temps or get a humidifier in there.

Hope this helps you but I ignored the problem on my last grow and I certainly paid for it.

Yeah I would definitely say that 20 is to low...Personally I think that 55 is about prime. I am lucky that my local climate is pretty damn good for indoor growing without so much weather control like temp & humidity. But do what you can to raise that level. Shoot for around 40-55 with temps at about 78 F. Proper conditions will make more of a difference than any nutrient can or remedy.

Starhawk said:

I think you'll be okay with 20% humidity. My humidity stays between 25-30%, and my plants are fine. But more air circulation and ventilation is always a good thing. Good luck with your grow!

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myxedup said:

My plants from my 2nd grow got stunted really bad from temps in the mid to high 80's coupled with 20%ish humidity. It shocked them terribly bad and I went from a 3lb harvest on my first grow to 1 lb on this last one. Do Not be passive about that. Do what you can to either lower your temps or get a humidifier in there.

Hope this helps you but I ignored the problem on my last grow and I certainly paid for it.

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Do you think by adding one more 4 in in line duct fan 80 cfm at the bottom to bring more fresh air in or should i have it as another exhaust on another top hole?

I think by adding one more fan I will have more ventilation and lower the temp to 80 or less.

Well you have to consider your starting conditions. The fresh air may not do anything for the humidity situation if it is of low humidity. I think adding more circulation will probably make the problem worse. This is another reason why most people use AC units, yes the cool air is nice, but it reacts with the warm air to create humidity. Just get some more moisture up in there.

The Ruiner said:

Yeah I would definitely say that 20 is to low...Personally I think that 55 is about prime. I am lucky that my local climate is pretty damn good for indoor growing without so much weather control like temp & humidity. But do what you can to raise that level. Shoot for around 40-55 with temps at about 78 F. Proper conditions will make more of a difference than any nutrient can or remedy.

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When I had mine in that range they developed stem rot and died. I think it was the lack of air circulation because I kept the door closed most of the day.