When I've had problems, it's usually powdery mildew. In my indoor garden, I think of 70% RH as the beginning of the danger zone. When my RH gets up there (usually in summer, in flower), I put a dehumidifier on a controller set to 60% in the tents. This is not to say that you can't grow above 70% RH, especially if you can provide a ton of air movement. Just describing my experience with my own grows.

What is the RH of the air outside the tent? If it's high, you might need a dehumidifier. If it's low, then the humidity inside the tent must be coming from the plant or the soil. That's the way I look at it. How big is the plant and how often do you water it?

Close tent completely and run inline fan on max nonstop or set upper range to start at 45% rh.

If you have proper ventilation you can get away with pretty high RH. Usually end flower around 55% RH, but last run we never dropped below 60%.

70+ is on the higher end, you're not going to get the transpiration that you're looking for in late flower the RH that high. You could also run into issues with PM, mold, and various other pathogens if your ventilation isn't on point.

If your lung room has high RH you'll need a dehumidifier to get the RH down.

ArtfulCodger said:

When I've had problems, it's usually powdery mildew. In my indoor garden, I think of 70% RH as the beginning of the danger zone. When my RH gets up there (usually in summer, in flower), I put a dehumidifier on a controller set to 60% in the tents. This is not to say that you can't grow above 70% RH, especially if you can provide a ton of air movement. Just describing my experience with my own grows.

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The air movement is good, but i can't afford a proper dehumidifier and running the AC would make too expensive for now, unfortunately. Thanks!

LoveGrowingIt said:

What is the RH of the air outside the tent? If it's high, you might need a dehumidifier. If it's low, then the humidity inside the tent must be coming from the plant or the soil. That's the way I look at it. How big is the plant and how often do you water it?

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Outside is 69% and some days is even higher, so i need to run the AC to help it, but that would make too expensive for now, unfortunately.

Kamisama said:

Close tent completely and run inline fan on max nonstop or set upper range to start at 45% rh.

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Alright, i'll try that! Right now i have an inline fan but since it's getting air from the outside, i doubt it'd ever get below 70%.

CityHerbs said:

If you have proper ventilation you can get away with pretty high RH. Usually end flower around 55% RH, but last run we never dropped below 60%.

70+ is on the higher end, you're not going to get the transpiration that you're looking for in late flower the RH that high. You could also run into issues with PM, mold, and various other pathogens if your ventilation isn't on point.

If your lung room has high RH you'll need a dehumidifier to get the RH down.

Click to expand...

The ventilation is quite good, i'm actually impressed the strenght my inline fan could pull air and move the whole plant, my biggest issue with a dehumidifer is that i would need to run the AC instead, since i can't afford a standalone one, so it would make my bill quite expensive.