High humidity in new grow tent help

Hello folks! I just got back into growing took a few years off due to children but we’re back up and running. With my current setup my RH is around 75-91 humidity in my room ( currently in veg ), but I need to figure out how to get it lower. I’ve ran this same setup before but all of a sudden my RH is crazy high.

here’s my setup

4x4 tent ( 15 plants 1 month veg )
Portable ac hooked up to 2 400 watt cool tubes.
6” inline fan 440 cfm pulling the ac air through the cool tubes exhausting into the bedroom
1 9” Oscillating fan 1 4” oscillating fan blowing in the room.

currently have no exchange of fresh air. I do have another 4” inline fan. I don’t know if I should push fresh air in? Or pull air out with it?

my room temps are perfect 71-79 degrees. I’m finding my 6” ducting is sweating from the ac running through it. I was using metal ducting ( sweating really bad ) switched to plastic flex duct got a little better.

I put two damp rids in which barley helped at all. I have a 10x10 tent on the way and 3 600 cool tubes. Would like to get this under control before I move to the bigger room. I’m looking at dehumidifier but I’m hearing that raises the tents overall ambient temp a lot. Any other advice would be great.

can get pics if need be of setup.

tldr; room temp perfect 71-79 overall RH ridiculously high 75-91 need to fix

You need to exhaust the humidity out of the building, don’t run ac through your cool tubes, just dump the heat outside.

If I don’t run the ac through the cool tubes they get way to hot?

TooFastxForYou921 said:

If I don’t run the ac through the cool tubes they get way to hot?

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I would switch to 600w hps/ mh. They are more efficient than 400w hid lights. I run three 600s within cool tubes in a 4x8 with two extractor fans with two of them being on a single 440cfm fan and it stays at perfectly reasonable temperatures. I also ran two lights in a 4x4 the same way without any real issues without ac.

Maybe a picture will help: https://www.dudegrows.com/grow-room-set-101-thecapn/
This is a good setup for winter because the grow lights heat up air coming from outside, for summer I would reverse the flow and push hot grow light air out of the building. The AC should be used to cool the grow room air.

I was having big problem with same thing last week i live In the UK and sometimes outside is 80-90% humidity so the fresh air I pull in is always a bit moist lol so I've had to buy another dehumidifier and another clip on fan seems to be working atm but then again the humidity outside is better atm lol

Thanks for the responses! This is how I’m running it. I added a 4” inline fan blowing in and I’m now at 59% rh I live in MS so very tropical weather.

anexgrower said:

Maybe a picture will help: https://www.dudegrows.com/grow-room-set-101-thecapn/
This is a good setup for winter because the grow lights heat up air coming from outside, for summer I would reverse the flow and push hot grow light air out of the building. The AC should be used to cool the grow room air.

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So you think I should use my 6” fan to suck hot air out and use my portable ac to blow cold air in the tent?

TooFastxForYou921 said:

So you think I should use my 6” fan to suck hot air out and use my portable ac to blow cold air in the tent?

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are you planning on flowering all those in that tent? you will definately need to suck out the hot air and replace with cold air those plants are going to way overfill that tent in my humble opinion

osowhom said:

are you planning on flowering all those in that tent? you will definately need to suck out the hot air and replace with cold air those plants are going to way overfill that tent in my humble opinion

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Good point, are you growing regular seeds and going to get rid of the males?

1) I would get rid of that cardboard & duct tape rig and let the AC cool the whole room, for various reasons.
2) run the hose from your light through a can fan and out of the house (just like the hot air from the AC)

You will be making your room slightly lower pressure than the rest of the house, so fresh air will flow into the room which you need for plants to be healthy and humidity to not build up, and at the same time you are getting rid of most of the waste heat and not running the AC constantly.