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Hi. JBudz from England - Humidity and Temp issue

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Wondering if anyone can help?? I've gone into flowering stage on my WW x Bigbud but I'm having trouble getting my humidity below 50. And wen the lights go off they even rise to 62. I have my exhaust fan on max and leave nothing in my drip trays. Im also struggling to get my temp down as well. Im using cool tubes yet cant get my temp below 32 degrees. Where id like it down to 25-28. My intake air is cool from outside as well. Am I just needing to get a humidifier and put in tent or outside the tent for the air being pulled in? I dont know. Someone help please ?

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Welcome to StrainHunters, Jbudz.


Tough problem, also difficult for us to diagnose because we dont have eyes-on. 


Maybe the exhaust fan is not strong enough or the flow is partly blocked on its way outward.  Maybe the filter is too small or in need of replacement.


If your tent has inlet flaps near the floor, brace them open for more airflow.  The exhaust fan could be sucking them closed.


A dehumidifier in the surrounding room might help, but its operation is added energy cost and noise.


Cooltube, that means you are running energy-gobbling, heat-producing HPS or MH lamps.  Consider using a good LED grow lamp instead.  Its energy savings will amortize its purchase cost within a year of continual operation.

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Thanks for your reply. I had a feeling that it could possibly be the exhaust (I got it from china)! 


I don't have any flaps at the bottom of my tent either so I keep 2 duct holes open. 


I think I'm going to get a dehumidifier to try sort out tht issue and will look you try change to LED next time round. My tent is 2.4x1.2 and is holding 10plants. Maybe my size of tent and the exhaust power don't add up and all I have to do is change the fan. 


Any recommendations on LED suppliers?


Thank you 

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There are many many manufacturers.  I got mine through a seller on ebay.  What is important is determining the power of the individual LEDs, and the wavelength of each LED, to make sure they are delivering wavelengths and intensity that the plant can use.

You should first do some research online to learn which wavelengths cannabis enjoys in Vegg and in Bloom.  Find 2 or 3 charts and compare them.

Then when shopping for lamps, the sellers should be divulging which wavelengths their lamps deliver.  A good grow-lamp manufacturer or distributor knows what the plants like and he will have designed the lamp properly, and he should be proud to give you that info.  If not, ask them.  If they cannot or will not answer that, then probably best to avoid that seller. 

There is a category somewhere here in StrainHunters that discusses LED growlamps.  Maybe the StrainHunters search engine at the top of the page could be useful.

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Nice one! I think it's something I'll look into next time round.


What I've got going don't seem to be preventing any loss of growth/speed atm. 

Does the humidity and heat being that little high (32°c 55% lights ON & 23°c 60% lights OFF) really make much of a difference to performance?


This is my first one and people say not to get too tied up in the ity grity and just concentrate on getting thm through a cycle to see what it's like but I can't help myself lol.


Lollipopping for the first time was mental. I only done it the once, the night before I switched to 12/12 so wen I was finished it seemed like I butchered thm a bit as they were pretty bushy beforehand. Maybe I'll put some b4 and afters on and u can tell me wat you think?


Thank you BTW! 

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Alright j buds I'm in the UK too. I have had similar issues. I would get a lot stronger fan by the sound of things. Also make sure to vent it back outside not into the room you have your tent in as that will keep temps high in ur tent too. The only problem is your night time temps. But you can buy a little electric radiator to come on at lights off to counter that. I hope this helps u pal, never stop fiddling n tinkering till you achieve your perfect climate it's the most important part of it all n so much quicker when it's right. 

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Thanks Chemnutter!

I currently do have it flowing out of the room to the outside. 

My night time temp is at 22. I'm sure I read somewhere that it should be 10°c less thn when the lights are on....is this not correct? 

Can you give me advice on the Temps I should be trying to achieve?


Thank you 

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I usually go for 26-27 day time and 20 ish at night and that seems to work well for me. I would advise not to have a difference of 10 degrees or more between day and night as this shocks the plant and slows it down. The closer you can get that gap the faster you will grow. Also keep ur water temp the same as the room temp where possible.

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Your friends who suggest getting through a batch of plants give good advice.  Personal experience is the best teacher.


Chemnutters numbers and advice sound good too.  Actually, water a little bit cooler than room temperature helps to deliver more oxygen to the roots.


When you start flowering, however, the humidity will need to drop through that phase and stabilize around 45% in order to avoid mold issues.

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Thanks guys!! 


Finally got my humidity floating around 38-45 depending on wen they've been fed. 45 when they have. Also got the temp down to 28/29 day and 22 at night. 


I just added an oscillating fan on a stand. And placed a small box of non-scented dehumidifying pellets in the tent.


They seem to be thriving at the min. 


I'll update with a pic....

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