VPD Explained

Jewels

Tilts at Tables
Thanks for the eye, spy.
Trying to ween off the heater @ night. I thought if I pumped enough air in, during lights out, the humidity would stay down.
Maybe with all this rain, my intake air is damp.

Lights went off @ 33C humidity was 55
After four hours of passive exchange, humidity rose to 72 as the temp fell to 23C 20200523_172911-1.jpg
I kicked on fresh air intake and by 5:30pm temp had falling to 18C. Humidity improved to 62%
The trend did not hold. By 8pm humidity was back to 70% , I had to start the heater cycling again.

Light on now.
20200523_233324.jpg
Usually, with the heater cycling on 1, off 2 thoughout the dark, I can maintain 50% @ 27C. Kinda pricey; but it works.
I guess I am kinda lucky, to be in the desert.
With this much mass, I am quite powerless in influencing humidity.
The clouds will be gone soon. My dark temps may approach dry, 27 C's passively, in August, during the heat of the day. I will be serving up Taco's in no time.
 

spyralout

🌱🌿🌲🔥💨
Staff member
Administrator
Moderator
Thanks for the eye, spy.
Trying to ween off the heater @ night. I thought if I pumped enough air in, during lights out, the humidity would stay down.
Maybe with all this rain, my intake air is damp.

Lights went off @ 33C humidity was 55
After four hours of passive exchange, humidity rose to 72 as the temp fell to 23C View attachment 11862
I kicked on fresh air intake and by 5:30pm temp had falling to 18C. Humidity improved to 62%
The trend did not hold. By 8pm humidity was back to 70% , I had to start the heater cycling again.

Light on now.
View attachment 11863
Usually, with the heater cycling on 1, off 2 thoughout the dark, I can maintain 50% @ 27C. Kinda pricey; but it works.
I guess I am kinda lucky, to be in the desert.
With this much mass, I am quite powerless in influencing humidity.
The clouds will be gone soon. My dark temps may approach dry, 27 C's passively, in August, during the heat of the day. I will be serving up Taco's in no time.
All good man, I'm in a similar boat. Get as much learning as we can in now before the heat really hits. Then we learn how to deal with it in the heat. Experience is the best teacher. This is all really good discussion, sincere thanks to AM for putting up this thread, sparking up the interest in VPD and its amazing benefits. One size does not fit all with VPD charts, and bringing attention to this can really up one's game in this area.
 

Jewels

Tilts at Tables
Still have curiosities, about the mechanics of 'dark vpd'
Calvin is bust'n his ass all night, and barely cutting a profit, I have never solved a rubisco cube,, lots going on at sleepytime , that I do not understand.

In the absence of photosynthesis, how does VPD play into the dark ?
Is daytime for offence ?
Am I strictly shifting focus to defence at night (avoiding condensation, maintaining productive minimum temps) ?
Or are there environmentally advantageous conditions that will promote growth ?
Is dark time about thriving ? Or surviving?
 

spyralout

🌱🌿🌲🔥💨
Staff member
Administrator
Moderator
Still have curiosities, about the mechanics of 'dark vpd'
Calvin is bust'n his ass all night, and barely cutting a profit, I have never solved a rubisco cube,, lots going on at sleepytime , that I do not understand.

In the absence of photosynthesis, how does VPD play into the dark ?
Is daytime for offence ?
Am I strictly shifting focus to defence at night (avoiding condensation, maintaining productive minimum temps) ?
Or are there environmentally advantageous conditions that will promote growth ?
Is dark time about thriving ? Or surviving?
People with sleep apnea use a CPAP to help with breathing while sleeping. Some use oxygen tanks. Probably way more restful and "repairing" sleep. Similar concept applies to plants?
 

NotAquaMan

In Bloom
Still have curiosities, about the mechanics of 'dark vpd'
Calvin is bust'n his ass all night, and barely cutting a profit, I have never solved a rubisco cube,, lots going on at sleepytime , that I do not understand.

In the absence of photosynthesis, how does VPD play into the dark ?
Is daytime for offence ?
Am I strictly shifting focus to defence at night (avoiding condensation, maintaining productive minimum temps) ?
Or are there environmentally advantageous conditions that will promote growth ?
Is dark time about thriving ? Or surviving?
Not much transpiration at night stomata are mostly closed so running a lower humidity by 10-15% is ideal but not needed
 

DopeDaniel

Taste The Spectrum
IPM Forum Moderator
Figured I would drop this here in hopes of getting some comments from the smart kids.


I am at 8000ft and my unscientific opinion is the reason is a combo of light spectrum and intensity as well as whever is analogous do DLI when talking uv light, and atmospheric pressure. Air at altitude of same rh and temp has a lower enthalpy. These are the factors I believe they should look at to explain the higher co2 processing power of plants at altitude.

Edit: @spyralout I can't figure out why link wont work can you help?
 
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