Humidity - Peaks and Valleys, Averages?

[Nverinder716]

I’ve got a very simple cool mist humidifier in my 2x2. It doesn’t have an onboard humidistat, so I have it set up to an analog timer to deliver approx 30 minute bursts of humidity throughout the day. I’ve been focusing on getting the average RH% up higher with the new grow (Buddha Seeds Medikit CBD), so as to get my VPD in line with recommended levels. I’m not even sure how much VPD matter to me at this point, and I’m STILL not hitting under 1.00kPa on average. But I digress.

What I’m concerned about is when the RH% in the tent spikes way up before the end of a “shift.” Highest recorded so far is over 80%, and the lowest has been under 35%.

Do I need to be worried about these extreme but brief spikes, as long as the average RH% is hitting my mark (55% at the moment makes me pretty happy).

Feel free to discuss RH, temp, and VPD here! Turning the corner on 3 weeks with this, and it’s my first (intentional) photoperiod grow!!!

 

[JP1]

It's ok now but that could be a pretty big problem in flower. You can get an inkbird controller and plug your humidifier and exhaust fan into it. When the rh gets too low it'll kick on the humidifier and when the rh gets too high it'll kick on the exhaust fan

 

[Nverinder716]

It's ok now but that could be a pretty big problem in flower. You can get an inkbird controller and plug your humidifier and exhaust fan into it. When the rh gets too low it'll kick on the humidifier and when the rh gets too high it'll kick on the exhaust fan

right, but I can dial back the output to reduce the over average RH%, which I’ll do once I’m in Flower - would that be sufficient? At that point, I’d be surprised if the humidity spiked above 70%…

 

[JP1]

70 would be really pushing it in flower. I'd just pull the humidifier out of the tent at that point. But either way, you've got no worries for several weeks

 

[Mañ'O'Green]

@Nverinder716 If you have one bare foot on a block of ice and one bare foot on a hot stove the average is you are comfortable. This is the same thing you are doing to the plant. The stomata on the plant begin to close when ever the RH gets too high or too low. This actually is normal for a plant to do over a full day. The problem I see here is that your cycle is many and too fast for the plant.

Regulating RH is not easy. I have been battling it this grow because the filters on my humidifier stop wicking even though I am using RO water. it is a PITA but you really need to keep it more steady if at all possible. I have a dehumidifier and a humidifier. When the plants get bigger I only need the dehumidifier but when they are seedlings and small I need to add moisture.

You can see that the filter went dry on Jan 30 failed on Feb 1. I rinsed it out and restored partial operation. I have it holding above 40% (lights on) just barely. I will rework this humidifier before the next grow. I have new filter elements but I think the plants will be taking over soon.

Ps. I am running an experimental 8/4 light schedule to see if I can speed up time to harvest? Normally I run 18/6.

So do the best you can for now and plan to do something better in the future. These plants are much tougher than we give them credit for.

 

[Nverinder716]

@Nverinder716 If you have one bare foot on a block of ice and one bare foot on a hot stove the average is you are comfortable…
…So do the best you can for now and plan to do something better in the future. These plants are much tougher than we give them credit for.

Thank you for the info dump, truly! I may very well just look into a humidifier with a proper humidistat in it to see if it evens out the highs and lows.

 

[Mañ'O'Green]

Thank you for the info dump, truly! I may very well just look into a humidifier with a proper humidistat in it to see if it evens out the highs and lows.

Yeah, I was just trying to make the point that this is one of the hardest parameters to deal with in the scale we work in, and you are not alone. The bigger the space the easier.

 

[Cannaficionado]

What might help is managing the humidity of the space the tent is in.

Having a humidifier inside the tent does help but it will require lots of monitoring and cycling to keep the humidity at a stable level if the room its pulling air from is drastically different than the air inside the tent. So if you can get the room environment closer to the optimal ranges of temp and ph it will be much easier to manage the environment inside the tent.

Also playing with the extraction fan settings will help stability. Theres tolerances but if your fan is running too fast its just going to suck most of what the humidifier is pumping out, where if its running to slow the adverse will happen and it will begin to build up in the tent faster than the fan can extract it. Dont quote me but I think you can use an inkbird controller for this too so the fan cycles helping keep the humidity and temps in the desired range.

 

[Nverinder716]

Good news! New humidifier with built in humidistat seems to be doing the trick. Picked one up from Amazon, it’s very sparing on the water usage so far, and it’s maintained a very stable and consistent RH without the massive swings. The Medikit CBD looking good at day 25, topped and filling out nicely!

 

[Cannaficionado]

What might help is managing the humidity of the space the tent is in.

Having a humidifier inside the tent does help but it will require lots of monitoring and cycling to keep the humidity at a stable level if the room its pulling air from is drastically different than the air inside the tent. So if you can get the room environment closer to the optimal ranges of temp and ph it will be much easier to manage the environment inside the tent.

Also playing with the extraction fan settings will help stability. Theres tolerances but if your fan is running too fast its just going to suck most of what the humidifier is pumping out, where if its running to slow the adverse will happen and it will begin to build up in the tent faster than the fan can extract it. Dont quote me but I think you can use an inkbird controller for this too so the fan cycles helping keep the humidity and temps in the desired range.

That was suppose to say rh not ph.....i use those 2 so often now if I mis-type it gets auto corrected to one or the other