First Grow Tent Heat Issues

Any cheap ideas on getting humidity up? I’ve got domes on them now.

I leave some of the runoff in the drip pans and it raises the humidity like 5% inside the tent.


Damp towel hung over the top bar or suspended by hangers
Wet dishrag draped over the fan
Air stone or fish bubbler in a bucket of water

Depending on how wet the towel is you can get dripping. Have in my notes to myself “Wet towels drip, dummy”.


I have a humidifier arriving today. I am curious how much this will affect the temp in the grow tent. Also, I am thinking of keeping the girls on a 24/0 light cycle. Does anyone have any experience with this that can give actual results showing a difference between this and say 20/4 or 18/6? From my own research it seems like it is more of a personal preference rather than any actual evidence that supports a lower/higher yield from any light cycle in regards to autos. Thoughts?
@hellraiser @Covertgrower @spudeater65 @dbrn32

1 Like

So when you grow autos (if you do) do you have a dark cycle?

I bugged the piss out of the mods a week or so back trying to understand the benefits / detriments to a 24 hour light cycle. Short thread. Start here:

As I understand it, once you hit your DLI for the plant you’ve maxed the growth for the day in the conditions you have (nutes, temp, water, co2, etc). You can hit it that total by adjusting light intensity in 12, 18, 20, or 24 hours. Doesn’t matter. Any extra light you throw at it will just be wasted electricity for the most part. You won’t hurt it in a 24 hour cycle, but you won’t get the 6 hours extra growth compared to an 18 hour cycle. Note that I’m not an expert, it’s just how I interpreted the feedback.


That was a great thread. Thank you for that. Yeah, I was not really thinking about extra growth (as I know you can only do as much growth as the plant will allow and there is a limit, plus there’s only so much CO2 unless you add more which I am not interested in doing). I am looking to maintain my temps at a comfortable level. My basement does get fairly chilly (like 60-64) and I am wanting to maximize this grow as much as possible on my end. So that totally answered my question. Thanks again for the link!


I plan on switching to a dark period in later stages, though, to promote the colors I am wanting from my Purple Punch. However, I will be keeping it on a 24/0 cycle through seedling/veg stages I think, following the info from that thread.

1 Like

Same thing I’m doing with some sprouts in an otherwise cold closet. 24/0 just to keep temp in the mid-70’s.

1 Like

I don’t grow autos so I try not to talk on the subject too much other than general plant issues. I’ll tag a couple auto growers. @Nicky @Not2SureYet


Thanks @Hellraiser I saw @Nicky typing here too. This is just my o2 that I have found from growing autos my self. All my plants, autos of photos need a dark time to rest. I have grown autos in a 12/12 to a 18/6. I do start all my little ones off on a 20/4 though for the first 4 or 5 days. In my current grow. I have an auto started on a 13/11 and is now on a 12/12 and doing good. I my self normally use a 16/8 for autos if just doing them and no photos mixed in. My room temps are a low of 61 and highs at a 84 degree average. I proved in my first grow. You can grow autos on any time over a 12/12. I don’t get into the DLI deal. Only because I have my grows dialed in all ready. So I know what works best for me. Nicky varies a little from how I grow. So you can learn a lot from him as well. We both kind of learn from each other I think now.


Thanks @Hellraiser

Autos can survive on any light scedule you give them, however I recommend a 20/4.

A while ago there was a group poll over on autoflower network and it showed 20/4 is the most popular light scedule with 18/6 in 2nd.

The comments section was full of people who have tried to run 24/0 but the majority of those that grow that scedule on multiple grows with different plants noticed that deficiencies were more common.

A light scedule won’t effect the yeild, the amount of light in a 24hr period will and that is why we focus on measuring light in Daily light interval, aka DLI, I have written a guide on this topic here.

Many people require 20hr of light to get ideal DLI when they don’t have top of the line lights, and others in cold climates prefer it because it’s proving heat (like in your and my situation) but there is no difference to the auto be the light be 12hr or 20hr if the DLI is the same and the environment remains ideal.

An ideal environment in all aspects greatly effects growth and yeild, ideally day Temps should be 79f this has been the optimal growth temp range as determed by Utah state cannabis study with Dr. Bruce Bugbee.
Keeping the humidity ideal for that temperature and the growth state of the plant is where your vapor density chart comes into play, cannabis VPD chart. This is a good guide but using a laser temp gun and inputing your own into a custom VPD chart depending on leaf temperature difference to air temperature is ideal (but not needed)

The best way to control this is with a AC infinity exhaust fan and using one of their controllers, setting the values. If you don’t have an AC infinity then you can buy an inkbird temp sensor and plug it into your exhaust fan.

Then get a modern humidfior that has a humidity sensor and values built in so you can set your humidity to 70% or whatever is recommended by the VPD chart.

In a colder environment it’s important to keep the plants and pots off a cold floor so use a riser of some sort.
A space heater will go along way in growth of your plant, I would set it for the same times as lights on, timer, but then have it shut off Durring lights off.

Lower Temps at night will help mildly stress the plant and produce better terpenes and canaboid levels.

I’m in agreement with everything @Not2SureYet is saying, as he said we learn from each other as we have both had a passion for autos for years and for the most part we see eye to eye on things. We each have our own ways on certain things, and finding what works for you is always best. I try to give values to everything that have been backed by research or vast amounts of user input and experience (in the lack of available research) as this helps new growers go shoot for an ideal and get as close as they can while learning what they can and can’t make work for them.



Thanks for that!

Yeah, that was exactly what I was looking for. I’m not saying that I do not value opinions of folks on this forum (I have used a lot of them and mostly it has worked out for me), but I was looking for cold hard facts to support one way or the other. Thank you very much! And thank you, too @Not2SureYet for excellent answers!

1 Like

I don’t grow autos, but I have vegged on 24 hour light cycle.


How old is that?

I tried24/0 but found out it was too much Light for the girls ,they need naptime! I run 18/6 right now Have one auto plant and one photo so I settled in 18/6 Girls are growing well DLI is up 49. to 63 with the light 3 feet above the girls.I added back my Vivosun Led 1000 to hit the seedlings with a closer light. Girls are taking off I cant tell you how long they sat there. But I will say maybe two weeks vegging and growing like little bushes. Pruned so under leaves to open up some light to the other parts of the plant.


About 6 weeks


That’s a pretty cool device you got there. I looked them up real quick. Do you just use that for seed and veg?

I will sometimes start plants under light with res removed. This one just hung out a little longer than normal.

1 Like