So, VPD’s ideal range is proven to be 0.8 -1.1 range, but I’m finding that keeping within the traditional range of 40%-45% humidity (to avoid mold and mildew growth on buds), means that keeping the temperature range between 75F-82F means your VPD is going to be more like 1.7-1.8 which is way higher than is proven ideal for transpiration and nutrient uptake etc… So, long story short to be in the ideal range (0.8-1.1) for VPD your temps need to be like 78F-82F and humidity needs to be like 60%-65% (these aren’t dead on numbers, they are approximations to support my question or point). Bear with me, this means that traditional 40%-45% humidity range for flowering at any stage is not ideal, because if you sacrificing air exchange for low humidity, you can’t reach the ideal VPD range. so how do we raise humidity and avoid mold? I think the secret is more than enough air exchange and consistent humidity upwards of 60%. IF there is enough air exchange I think the ideal VPD can be reached. Depending on how much stock y’all put in VPD, the science seems to support it, it may just be a case of people growing good enough bud where they don’t want to mess with what is working, but perhaps a grow where during the entire duration the VPD was ideal, may be the difference between a world class grow and a grow you are satisfied with? Thoughts? Here’s a treat picture just for giggles while you ponder this epic post.
when my VPD is high and temps are high, i raise my humidity and it equals out but i also increase the airflow to prevent the mold from forming. i could be wrong in this process but no mold or mildew so far (knock on wood).
Ever since I started monitoring my vpd,it has improved my grow.
Early flower I keep mine around 75-81° 60-65% RH and in late flower 77-82° RH 55% but I always have atleast 2 osculating fans running,sometimes 3 lol.
Sounds about right, I’m guessing those late flower numbers your VPD is about 1.4 or so? More evidence that killer bud can be grown and the closer you can stick it to that range of 0.8-1.1 the better it gets I presume!!
i play with it and try and keep it the non frying zone
Just out of curiosity what do you consider the “frying zone”?
No, I think you got it right and basically mirrors my original post. If VPD is something one wishes to consider they will likely have to increase humidity and in turn increase air flow/exchange in order to get nearer the VPD sweet spot .
VPD of higher than 1.6, ive came home with an empty Humidifier and it was reading 2.2 a couple of times but i got it back down and they were fine
Yea,that’s with a -2 leaf temp🤙🏻
I know this post is older but i was thinking same exact thing. I’ve had drooping issues and only thing I changed was my humidity when I went into flower. My VPD was way higher than it should be according to VPD charts yet my temp and humidity were right where they should be according to every single grow chart or book ever published. I’m now focusing on vpd to see if it helps even though it worries me having to have more humidity coming. I do have fans and plenty of intake / exhaust but still always scares me especially being new.