Why not only vegging where does the exhaust blow to when out fan is running, If outside maybe look at keeping that lost heat inside the shop or garage you are using to grow.
In have the same set-up, 4" AC Infinity in and 6" out, and the large AC Infinity large humidifier. Managing RH has been pretty easy. I do have a split unit H-vac in the shop. Running the split on heat dries the air quickly. I tried it and ran through 4 gallons of distilled water daily. Both cost $$$
Sure, other than smell issues, which you said was not a problem. it will put stress on your seams and zippers.
What’s VPD?
en.m.wikipedia.org
www.perfectgrower.com
A myth.
Did a quick Google on "The Mythology of Vapor Pressure Deficit". Miraculously, the very Wikipedia link in my previous post came up first in the search. Not a myth.
Good explanation of VPD here.Vapour-pressure deficit - Wikipedia
I honestly didn't know the exact definition before you posed the question. But, the link gives a definition and explanation. All I know is that for cannabis, seedlings and early vegetative stages, the number for vpd should be about 0.8. Then in vegetative to early flower, it should be closer to 1.0. And finally, early flower to chop, 1.2. That is what I recall from when I did read up on it a bit. For me, I noticed that my plants seemed to thrive the more I tried to adhere to these numbers. It seemed like alot of humidity to me, so I made sure I had plenty of airflow in my tent, to avoid any mold. The vpd chart in this link tells you where your temperature and humidity need to be to fall in an acceptable range.
VPD Chart (Vapor Pressure Deficit) - Perfect Grower Knowledge Database
VPD Chart (Vapor Pressure Deficit) by Perfect Grower
That VPD chart doesn't discuss the fact that VPD for optimal grow is different for the different stages of growth. It's a good start but there's more to it. And it does mention calcium uptake, which is really good to see.Vapour-pressure deficit - Wikipedia
I honestly didn't know the exact definition before you posed the question. But, the link gives a definition and explanation. All I know is that for cannabis, seedlings and early vegetative stages, the number for vpd should be about 0.8. Then in vegetative to early flower, it should be closer to 1.0. And finally, early flower to chop, 1.2. That is what I recall from when I did read up on it a bit. For me, I noticed that my plants seemed to thrive the more I tried to adhere to these numbers. It seemed like alot of humidity to me, so I made sure I had plenty of airflow in my tent, to avoid any mold. The vpd chart in this link tells you where your temperature and humidity need to be to fall in an acceptable range.
VPD Chart (Vapor Pressure Deficit) - Perfect Grower Knowledge Database
VPD Chart (Vapor Pressure Deficit) by Perfect Grower
Great post!Good explanation of VPD here.
VPD is a way of expressing ("putting a number to") different combinations of temperature and humidity. It's similar to the "feels like temperature" vs the ambient temp and it's really important when growing cannabis.
The big issue is that VPD is what drives transpiration and transpiration is as important to a plant as breathing is to a human. A small change in VPD will change how nutrients are taken up. Good example, a 0.2 unit change in VPD will cause a 20% change in Calcium uptake.
Below is a graphic I snagged from a Bugbee video. I've found it really helpful in the 2 ½ years that I've been growing for setting up my tent and my processes. I use "processes" intentionally, one reason being that we tend to get better outcomes when we do things with consistency and we get those outcomes while reducing resource use (time, labor, material, and money).
Of the nine parameters, controlling VPD allows us to control temperature and humidity, so we're ¼ of the way there.
View attachment 5348500
How to measure and control VPD?
Controlling VPD can be a PITA but it depends on the grow environment. I started with a PulseOne, an Inkbird for a humidifier, and an Inkbird for a heater. All of that went away when I installed an AC Infinity Controller 69 and their humidifier. My 2' x 4' grow tent is in a garage in Southern California and I grow only in Fall and Spring because that's when the temps (in the garage) are in the 70's, give or take. I don't have to do much with temperature, which is good because I can't do too much about temperature, but I can control RH between the humidifier in the tent and a Walker dehumidifier in the garage.
How does it work out? Pretty darn well.
My baseline grow is a pound per grow and part of that is because VPD is always in range. Per above, 0.8 for seedling, 1.0 for veg, and then rising gradually to 1.2/1.3 in flower.
Below is a screenshot of the app for the C69. It's a little warm in there ATM(my grow light is at 246 watts to generate the 700µmols that my plants are getting) so I'll need to dial up the inline fan (my fans are from AC Infinity so I can turn it up from my phone).
Check out the green line — it stayed at 0.8 for the time when the plants were germinating and in early veg, then it went to 1.0. With the AC Infinity controller, you can set the software to maintain a VPD value and, in this case, it turns the humidifier on and off to maintain that value. As usual, VPD hasn't varied more than 0.05 units and I have had to do nothing except buy the piece parts (the Controller 69, the humidifier, the tent fan, and the inline fan) and set them up.
View attachment 5348507
How well does it work? Pretty well.
The first picture is the current grow. They're 30 days old and one will be leaving the res since there's not enough room for two.
The second picture is a photo grow, a "shrubbery".
Third picture are two autos. I think that was the last grow where I grew two plants. Too much hassle.
I've never not managed VPD because VPD is so important to getting good outcomes. Many grows that I see are more a tribute to how well cannabis can survive despite the efforts of the grower. Prior to starting to grow cannabis, the only thing I had grown was old but, along the way, I got convinced that sometimes it's a good idea to do what's in the directions. That's not for everyone, no argument there, but I really do think that getting VPD under control and giving "lotsa light" are two huge factors in growing cannabis.
And if you think I've been banging on about VPD, (don't) ask me what I think about grow lighting!
View attachment 5348510
View attachment 5348511
View attachment 5348513
dude they look nice and healthy but here i do 0 vpd management and this small tent doesnt look much different to me. if i follow vpd i’d either get mold or have to keep my temps way lower. not gonna work. i cant keep 75% rh in this tent to stay in that green area. if it was up to me i’d even go lower than the 50% it has now but thats as low as my dehum can take it down.Good explanation of VPD here.
VPD is a way of expressing ("putting a number to") different combinations of temperature and humidity. It's similar to the "feels like temperature" vs the ambient temp and it's really important when growing cannabis.
The big issue is that VPD is what drives transpiration and transpiration is as important to a plant as breathing is to a human. A small change in VPD will change how nutrients are taken up. Good example, a 0.2 unit change in VPD will cause a 20% change in Calcium uptake.
Below is a graphic I snagged from a Bugbee video. I've found it really helpful in the 2 ½ years that I've been growing for setting up my tent and my processes. I use "processes" intentionally, one reason being that we tend to get better outcomes when we do things with consistency and we get those outcomes while reducing resource use (time, labor, material, and money).
Of the nine parameters, controlling VPD allows us to control temperature and humidity, so we're ¼ of the way there.
View attachment 5348500
How to measure and control VPD?
Controlling VPD can be a PITA but it depends on the grow environment. I started with a PulseOne, an Inkbird for a humidifier, and an Inkbird for a heater. All of that went away when I installed an AC Infinity Controller 69 and their humidifier. My 2' x 4' grow tent is in a garage in Southern California and I grow only in Fall and Spring because that's when the temps (in the garage) are in the 70's, give or take. I don't have to do much with temperature, which is good because I can't do too much about temperature, but I can control RH between the humidifier in the tent and a Walker dehumidifier in the garage.
How does it work out? Pretty darn well.
My baseline grow is a pound per grow and part of that is because VPD is always in range. Per above, 0.8 for seedling, 1.0 for veg, and then rising gradually to 1.2/1.3 in flower.
Below is a screenshot of the app for the C69. It's a little warm in there ATM(my grow light is at 246 watts to generate the 700µmols that my plants are getting) so I'll need to dial up the inline fan (my fans are from AC Infinity so I can turn it up from my phone).
Check out the green line — it stayed at 0.8 for the time when the plants were germinating and in early veg, then it went to 1.0. With the AC Infinity controller, you can set the software to maintain a VPD value and, in this case, it turns the humidifier on and off to maintain that value. As usual, VPD hasn't varied more than 0.05 units and I have had to do nothing except buy the piece parts (the Controller 69, the humidifier, the tent fan, and the inline fan) and set them up.
View attachment 5348507
How well does it work? Pretty well.
The first picture is the current grow. They're 30 days old and one will be leaving the res since there's not enough room for two.
The second picture is a photo grow, a "shrubbery".
Third picture are two autos. I think that was the last grow where I grew two plants. Too much hassle.
I've never not managed VPD because VPD is so important to getting good outcomes. Prior to starting to grow cannabis, the only thing I had grown was old but, along the way, I got convinced that sometimes it's a good idea to do what's in the directions. That's not for everyone, no argument there, but I really do think that getting VPD under control and giving "lotsa light" are two huge factors in growing cannabis.
And if you think I've been banging on about VPD, (don't) ask me what I think about grow lighting!
View attachment 5348510
View attachment 5348511
View attachment 5348513
Thank you.
I think you're saying that controlling VPD isn't for everyone. No argument there. That's the situation we're in growing cannabis outdoors.dude they look nice and healthy but here i do 0 vpd management and this small tent doesnt look much different to me. if i follow vpd i’d either get mold or have to keep my temps way lower. not gonna work. i cant keep 75% rh in this tent to stay in that green area. if it was up to me i’d even go lower than the 50% it has now but thats as low as my dehum can take it down.
and this grow was a shitshow from the beginning btw extremely neglected due to health issues. so all in all yeah vpd, not for everyone
nah i will keep my hygrometer to measure rh to avoid fungal problems and measure temps to keep it cool enough to preserve more terpenes.
my house is just by the sea so rh is always very high. plants are always happy though they dont really care about vpd too much ime. i try to keep it at 40% and it fluctuates between 40-50%. if it works for you how great but its not for me.
