Ventilation and humidity

I believe I read one way to combat high humidity is with airflow. I guess my question is this, if there is constant fresh air in the tent along with an oscillating fan in the tent will that prevent bud rot? I do have a dehumidifier, but when it is on it makes the temps in the tent almost 80 degrees, and I am not sure if that is too hot so I run it sparingly. I don’t run it when I’m not home since I cannot monitor the temps.

Short answer is that humid air can move. If it is really high or low, circulating won’t change the humidity drastically.

If you live in a desert or a swamp, a fan can only do so much.

do you have an exhaust for your tent? i believe exchanging the air helps.moving air prevents the bacteria from settling, moving air is also good to help strengthen stem. 80 degrees isn’t to hot with moving air

Ok. Yea I have an exhaust that will create negative pressure, but I also have a fan blowing air for an intake, as well as an oscillating fan. The humidity has been up to to 70%, buy usually is between 55-65.

@BobD1 what is the hottest temperature that is acceptable?

80 degrees isn’t a big deal, but that humidity can get you.

Exchanging air can help, but what’s the humidity of the fresh air you’re bringing into the grow? If it’s already high, having a fan isn’t going to lower it. And if you’re exchanging the air relatively quickly, the dehumidifier won’t help as much either.

@dbrn32 I am not sure of the humidity outside of the tent, but the dehumidifier when I run it is on outside of the tent. So when the air exchanges, it is with the dehumidified air…I am worried if I run the dehumidifier more the temps will go up to around 85…

1 Like

I have read high 80’s with lots of air, but I am not sure. I had temps in the mid 80’s with lots of air movement, an intake, an exhaust and three circ fans going, didn’t seem to hurt the plants. I used a dehumidifier, but exhausting inside the house made it to hot inside tent. they even smelled awesome in the mid 80’s when the humidity was right

@BobD1 this is my first grow and I want to make sure something comes of it lol that’s why I am so worried about the humidity. Next grow I know what to change, but I don’t want this to go to waste. :frowning:

this is my first grow too. can you exhaust the dehumidifier air outside? Damp Traps help alittle

@BobD1 the best I can do is just open the basement room door to the other room and let the air out that way…block windows really don’t give me an option to vent outside. :frowning:

1 Like

are you close to the dryer vent?

Personally, I would be more worried about humidity than being mid 80’s on canopy temps. Mid 80’s isn’t that bad. Even if it hampers your grow a little, so what. If mold sets into your buds you’ll be tossing it all.

Just the way I would treat it.

1 Like

@BobD1 I can be close to the dryer vent… are you saying exhaust the tent air to the dryer vent?

@dbrn32 that’s a good point. I didn’t know if higher temps would kill them off as well. It has only been a struggle like this for a couple days so hopefully no damage has occurred yet…


that would be one way, I was thinking of the dehumidifier tho. if you have everything exhausting into the room that your tent is in, your intake is sucking that heat back into the tent

High temps can, but I don’t think mid 80’s is even very close to the point that will happen. People grow outside in 100+, and plants survive. Granted, that’s not a great target. But I wouldn’t sweat 85 at the cost of mold. Get the humidity in check and I think you’ll be fine.


Perfect. Now I need work to be over so I can go home and mess with things :frowning:.


@dmykins the rule of thumb is if you can stand it then it’s OK for the plants. 75 to 85 is nominal. But let’s talk about humidity:

Relative humidity is 2 words. The value we get is derived from the temperature. As the temps drop, the air is able to hold less water so the RELATIVE number goes up as well as the dew point. A more important datum but WAY harder to obtain (requires a spinning wet surface taking temperature measurements of it). So we use RH.

Now, if your grow space has a temp of 70° with 70% RH the air is holding 18.79 mg/l of air. At 80° you have the same amount but the RELATIVE humidity drops to around 62%.

IMO you would be best served to remove moisture from the grow space and let the plants deal with the increased heat within reason. In flower. Veg is no biggie.

Hope this helps.


@Myfriendis410 that makes sense. These guys are in flower so that’s why I am asking. I will concentrate on lowering the RH and deal with the heat. If anything, the heat may get up to 85 degrees…but that would be in an extreme case.

1 Like

My girls love 85°: that’s tanning weather lol.

@Myfriendis410 haha. Well my girls may also enjoy it. :):grin: