Vpd and what it means

[Justlovetogrow]

Can someone plz teach me more about what vpd means I know I could research just trying to shortcut with some real grower knowledge

 

[FourthCity]

VPD (vapor pressure deficit)

Ok i was gonna sit down and write out a whole article but i have been lazy so instead instead I'm going to copy paste because im lazy. This is not my work so let start. You may find this very long but its worth the read. Some may want to skip ahead. I have added here and there to what i feel is...

www.thcfarmer.com

 

[Justlovetogrow]

Thank you awesome thread

 

[Justlovetogrow]

So if I have temps around 25degrees I should have my rh sitting at 65 or am I reading this wrong seems in the zone for powdery mildew to me very interesting man

 

[One drop]

27 deg 50 to 55 th is good I’m just clipping 26 8 . Od

 

[PpmOver9000]

Dehumidifier or Portable AC?

Have a read. There is lots out there you just need to look past the mountain of old info. The reason ppl think 40% o think is due to not understanding how significant that humidity spike can be at lights out. This is why VPD got a bad rap from those ppl with the same view. That and it was...

www.thcfarmer.com

Solid reply by @Aqua Man in another thread. Jist of it is that 65% and 25C is fine but it's very important to climate control for the night period. RH spikes when lights go off is what causes PM, not just RH by itself. According to the paper he references 65 is the ceiling, so maybe go 55 or 60?

 

[Justlovetogrow]

Yea I read the chart wrong cheers for your input one drop I really need a better dehumidifier my humidity just flat out refuses to drop below 58percent it’s driving me crazy

 

[Justlovetogrow]

Thanx ppm this humidity thing really getting to me man don’t won’t no pm on my baby after all the work that goes in live and learn and learn some more I suppose

 

[PpmOver9000]

you need mooooree powweeerrrr! *tim the toolman voice*

 

[Justlovetogrow]

Yea man I know I’ll get on top of it soon all the grow shops round here charge out the arse so I’m going to have to go through amazon or something which takes 2 weeks to get here by then could have troubles I have 3 fans inside my little 1.2mx1.2mx2.0 grow tent with 6 inch extraction fan still to no avail as u say need more power

 

[One drop]

Yea man I know I’ll get on top of it soon all the grow shops round here charge out the arse so I’m going to have to go through amazon or something which takes 2 weeks to get here by then could have troubles I have 3 fans inside my little 1.2mx1.2mx2.0 grow tent with 6 inch extraction fan still to no avail as u say need more power

Try constant passive air intake I did and have had great results . Od .

 

[Justlovetogrow]

Yea I have got an exhaust and 3 fans with 10 inch ducting for intake I do have my hygrometer sitting at the base of my pot so maybe it is better humidity at canopy level dunno

 

[Zoneshityee]

Also keep in mind that depending on your light, your target temp/ will differ.. you want lower temps With MH//HPS and higher with LED

 

[Zoneshityee]

Yea I have got an exhaust and 3 fans with 10 inch ducting for intake I do have my hygrometer sitting at the base of my pot so maybe it is better humidity at canopy level dunno

The higher up in thengrownarea, the lower the humidity

 

[Justlovetogrow]

Am running 600watt hps non air cooled hood batwing I think they are called?

 

[Zoneshityee]

So you want slightly lower temp, those lights can cook the babes

 

[Aqua Man]

Its hard to get PM when you have good airflow.

Prune any leaves that are stacking or sitting on eachother. Make sure you have good airflow through and below the canopy.

When doing indicas or ondica leaners they like it on the drier side of VPD and Sativas more on the humid side.

As @PpmOver9000 mentioned pay close attention to the humidity spike at lights out... it can often times get close to the dew point and that a real danger zone for PM.

 

[Justlovetogrow]

Thanx aqua man I def have good airflow everywhere just tryin to get it dialed in is all thanx for the reply mate