24 hour light cycle for stable humidity

[joeman098]

Hey,

I cannot seem to get my humidity under control. I have a dehumidifier with my plants but it doesn't do much despite it being a costly one. They are autoflowers and have had them on a 20/24 light cycle. I am now in flower and don't want bud rot. The humidity can get over 60 percent with the lights off. I have ready a lot of different opinions about 24-hour light cycles and have never read something negative about them being on that way during flower.. any feedback? Today I put them on 24 hours and am hoping for some advice. Thanks!

[changeofpace2014]

A little more information on your setup...is it a tent, basement,etc what type of ventilation / CFM do you have?

Little info 4 u.. I grow in a tent with lots of ventilation, with that being said there is only a point or two difference between the humidity outside the tent and inside.. I think it would be really hard to lower humidity in the tent because of the air movement (u should have), however you could probably lower it in the room your grow opp is in.

[changeofpace2014]

my humidity runs 50% outside the tent and between 51 - 52 % inside..but I am in the north part of southern ontario lots and lots of snow today..

[joeman098]

1m2 tent inside with mars hydro 6in inline fine with temp control. Outside my tent its 62 percent and with lights on with the dehumidifier it's 56 percent. I also use autopots so there isn't exta humidity from watering. I live somewhat near the ocean in a humid environment a bit in the mountains...

[joeman098]

Should I move the dehumidifier outside the tent?

[3Berries]

Lights off is not problem at 60% IMHO. I would love to see that. I was limiting mine to 80% lights off, just went to 75% with the cooler dryer temps.

[changeofpace2014]

IMO I do not think there is time for the dehumidifier to work with all that air exchange,,,you should be replacing the entire volume of air in the tent every few minutes actually 3.. but if you move it out side and drop the entire area, it will bring in dryer air.. This is the way I see it..

[3Berries]

You aren't ever going to control humidity when moving large volumes of air at low temps. And usually dehumidifiers became quite inefficient when under 70F or so though the newer ones are capable.

[joeman098]

What if I raise the temps in the room a bit? It is normally 70 degrees in the room.

[3Berries]

What are you trying to get the RH down to? Right now one tent is lights on and 74F/61RH (a bit dry) room is 64F/55RH. and the other tent lights off is 61F/74RH input air is 64F/56RH.

Have you heard of using Vapor Pressure Differential to target RH and temp?

[Going2fast]

The higher the temp the higher the humidity can be. If you have a good breeze going you will be ok at 60% and 75 degrees. I start worrying when it hits mid 60s. But yeah you have to lower the humidity in the room. The fan you have may be overkill for that tent but I went that way also for being able to run it at lower settings.

[Blowdout2269]

I agree with what others are saying. Raising the temperature should lower the humidity. Quite significantly in my case. Coupled with good air movement, I think you'll be alright.

[dilvish]

how often are you watering? remember that moisture in the air has to come from somewhere. If the tent temperature is too high and the watering too much that can become a humidity problem. You said the temp was 70F in the room...what is the temp inside the tent?
Alternately, why not just open the tent and leave it open?

[joeman098]

I use autopots so there isn't any extra moisture in that way. I have the heat set to keep it at 72 inside and it is now 77 iin the tent. The humidity has gone down some putting on the heat a bit but its still about 55 percent with lights on and 60 with lights off which is the rooms normal humidity level as it is very humid here. I suppose I am still curious if I can just leave the lights on as they are now in flower and the roots are established.

[3Berries]

Get in the green zone

https://vpdchart.com/#F,55,77,77,0

[joeman098]

that chart is so helpful, thank you!

[3Berries]

Plants transpire with lights off too.

[changeofpace2014]

You might be able to utilize desiccant beads to dry the incoming air but you would have to use a 5 gal bucket or something for the intake to pass through first. These are renewable with a oven.

https://www.amazon.com/Premium-Indicating-Silica-Industry-Standard/dp/B013L31PQ0/ref=sr_1_1_sspa?crid=1KM6QUK7E512F&keywords=desiccant%2Bbeads&qid=1668892831&sprefix=desiccant%2Bbeads%2Caps%2C697&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

[dilvish]

I still think that since the temps are low (72F) the pots aren't drying out and you are then likely watering too much. At those temps you needn't water for 4 or 5 days. Just make sure the first 2 inches of soil are dry before you water again.

[joeman098]

They are autopots so that should avoid that issue I think...

[changeofpace2014]

having the same issue or simular one...my temps are low with 75% power and 1 light..Actually just turned on the second light a little while ago and moved a few plants under...This will bring temps up...Earlier when I had them both on in a dry run..the temps were going to be an issue and had to mod the tent..we shall see...but yes it is hard to dry out pots from a full fertigation in cools temps...

[Blowdout2269]

A good amount of air movement should help dry to pots from the top and sides(if using fabric pots) even when using firgitation methods.