High Humidity @ night

Newbie grower- 5 weeks into a Purple Kush veg. Problem @ night when the lights are off and temps are low the humidity spikes up to 70+.

Have a dehumidifier going plus 4 fans to circulate the air.

Worried when it comes to flower especially the later part humidity is way too high.

Any advice to reduce the humidity.

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You could use a small space heater or handi heater to raise night temp which will drop your r.h.

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Cheers @Allinherhead, I put a small heater in the room with a temp control. C how she goes.

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Let me know, i love a sucess story. I added a temperature controlled outlet to plug my heater into as extra protection. My heater before stuck on ond baked my grow now have redundant control peace of mind for $10.00. Also i keep smoke detector everywhere i have lights or heaters.

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Where is the room exhausting to. If exhaust is going into ling room thats a big problem. I had the same issues. Night time gets to 68 degrees and 70+ rh now i changed exhaust venting to my crawl space instead of the lung room and bam night time temps 65 to 70 and rh is now under 55 no dehumids or anything. Still working on a lottle bit of better numbers but im dialong it down quite well.


I have a small air filter hanging on top of my T5. That is pushing the tent air out…
I don’t have any air coming in, other then want the fans push around…

Hey @Allinherhead, been running a small heater fan - Inkbird temp controller in the tent…looks like it’s done the trick- steady RT @ 75 and RH @ 55-65%.
Cheers MB


Hey @Mark0427,
Only have a carbon filter pulling air out…
Don’t have air coming in…
I do have the tent slightly open during lights on, day time, but nothing (air) coming in…
Currently have inkbird temp control connected to a small heater set to kick in when RT goes below 73 which has brought RT up to 75 and humidity around 55-65. :crossed_fingers:t3:Things stay this way for a bit.

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Are you saying that you don’t have any vents open?

Awesome, thanks for the update

Vents r open during lights on

Sorry, so your saying that at lights off(when the problem occurs) that you have no air flow though tent?

Is there a differential in tent RH and ambient (room) RH.

Unless, I’m missing something then your problem is that you have no air exchange while lights are out.

Hey @Gammagoat

, maybe this will show u what I’m trying to say. Temps and humidity are stable atm with a small heater in bottom corner dialled into a inkbird temp gauge, kicks in when RT fall below 73 F.

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