Hi guys, tried to use search but cant find what i need.
Im get my ladies into flowering, in day time(lights on) i got about 40-50rh, but on night time , the rh rises to 60-70 is it ok, or i need to get some dehumidifiers?
You’ll always have a humidity jump at night as the plant respire more and the cooler air allows for more moisture. At 65-70% humidity without really good ventilation you’re running the risk of mildew or mold. So I’d run a dehumidifier to keep it in check day and night.
Side note: trichromes are an anti-desiccant, so keeping your overall(day+night) humidity at 40-50% you’ll also see more trichromes as the plant is trying to not dry out.
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It depends. As long as you are drawing air from outside and you have plenty of air moving around your plants via clip on fans or similar you should be fine. De humidifiers won’t correctly work inside a grow tent if that’s your grow area. You need to dehumidify the room it’s situated in. I defoaliate heavily to allow more airflow around them.
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I should have mentioned that. Me original post is under the assumption you were using it for the whole room.
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my grow are is room, about 3x4 meters, i have in and out fans , and 4fans moving air around the room, when lights on then fans blowing and sucking alot of air , but in the night time, they running on min and i got high rh. so it’s necessary to buy dehumidifier?
Could you expand on that? Because of the heat output or something else?
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They tend to short cycle a lot leading to possible blown fuses if you’re running your power to the limits as well as costing more electricity wise in the long run
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It’s better a humidifier be smaller and run all the time than larger and turn on/off all the time. The initial start up causes a power spike
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electricity bills is not main thing , if its alot better to keep rh same in night as in day, im gonna buy it tomorrow 
A dehumidifier gets hot yes so your humidity meter won’t give you the correct reading. Your also battling the humidity of the room the tent is situated in. Your far better getting the actual room humidity down that the tent is situated in and the tent should eventually follow.
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Its a room, not a tent
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Ah so it should work fine 
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Thank you, in flowering stage a rh should be about 40-50% in day and night?
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40 - 50 is fine. I struggle with humidity. At the moment I’m 5 weeks in bloom yet my humidity is 75%. I have excellent airflow from outside and a few fans moving the air around and like I said I defoaliate to allow enough airflow around the buds to prevent rot/mold/pm.
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oh sh** you must be kiving in very wet area. In summer when wheather is hot i could run my in and out fans in max , so i dont have a problems with rh, but now in wheather likes these , i cant run my fans on high power, cuz its to cold outside 
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could you possibly increase the air exchange at night? (add’l fans)
is the outdoor air dry(& warm) enough to exchange possibly?
the smaller dehumidifier sounds like a reasonable option.
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I’m north UK. It rains ALOT here 
.
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Fk , i see my tent spike up to 83 % rh and i have intake from outside and a clip-on fan in there , just like @Esrgood4u i stay a bit north of him and it’s raining most days and freezing cold at night -( when i have my lights on) …
Add some shredded paper in a small box/es to help take some moisture from the area .? -above the lights ??
(Just a thought)…
Good luck with your rh @Kingtut …
Gaz
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You could think about investing in a small low output heater to run during lights off. 65-70% isn’t THAT high (I’ve operated in 90+) if you were to add even a little bit of hot air to the room you should see a noticeable drop in humidity.
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