Humidity & VPD question, Help Wanted

Ph 007 · Jan 19, 2023

Hi people of earth

I was wondering if any of you can help me, it's about vpd

I'm running led grow on flower
3 weeks in today
Temps and rh are:

Day
Temps 80-83f
Rh 59-63% usually about 60%

Night
Temp 73-75f rh
Rh 48-58%
will be lowering night to 72-73f soon

The room is passive intake

My question is,
It this day rh to high At 59-63%

The vpd chart says temps 80-82f humidity You want is 50-60%

Im trying to find out if this hunisig is to high will it affect yield as it's nearly range.

I have a dehumidifier see, and it's 670w I can put this on when lights are on and get my room to stay 80-82f and rh 57-59% it will usually sit at rh 57% constant
But
Its cost £3 a day in electric to run this for 12 hours a day, it's on nearly constant dor 10-12 hours lights on , not cheap ..
If the rh at 57% is going to give more yield I may use the dehumidifier

The vpd chart Also says late flower
Temp 80-82f
Rh about 40-50%

The last week if flower maybe the last 2 week's I plan to lower my day temo to 75-77f and rh 45% not sure if it's good or not I seen someone else do this so I wanted to try it.

Or maybe run my room 81-84f to match my humdiy better

Cirroji · Jan 19, 2023

I would invest in a much smaller and energy efficient dehumidifier - something you’re going to want to have access to use - but at that cost it’ll pay for itself quickly

Ph 007 · Jan 19, 2023

Cirroji said:
I would invest in a much smaller and energy efficient dehumidifier - something you’re going to want to have access to use - but at that cost it’ll pay for itself quickly

The dehumidfer I have had two settings low and high low is 420w high is 670w
If I put it to low my rh is about 58-60% and in high 670e rh sits at 57%

It's passive intake see hard control rh

Ph 007 · Jan 19, 2023

Electric cost £0.35kwh rip off

freezeland2 · Jan 19, 2023

What are the leaf temps? Use leaf temps when calculating your vpd.

PipeCarver · Jan 19, 2023

Ph 007 said:
The dehumidfer I have had two settings low and high low is 420w high is 670w
If I put it to low my rh is about 58-60% and in high 670e rh sits at 57%

It's passive intake see hard control rh

Hi,...I'm in Canada on the east coast with a basement grow. I need to increase my temps to at least 76f higher is better 78f would be better but 76f works...check out my pics if you want. My daytime gets to 76f and night time 65f not ideal but it seems to work.

I need to add moisture when its cold here. my basement now is at around 50% in my flower tent that's great for them......... In my veg closet I add a humidifier to increase to 60 - 65%. I have to add humidity or they don't grow well at all.

The big thing for me is dehue I've 2 - 35 pint and a 30pint in the heat of the summer its 100% humidity here so both are running full blast 24/7 to get the humidity into the 60% range. I try not to flower at that time but shit happens.

Moe.Red · Jan 19, 2023

The primary issue with higher RH in flower is fungus. Above 60% is tempting fate, but is very strain dependent.

I'd be more worried about that than yield. Proper VPD sets max transpiration, therefore max photosynthesis potential, therefore max flowers. The difference between 60% and 55% may not even be noticeable in your final weight, but mold sure will be.

Madmax · Jan 19, 2023

No they aren’t cheap to run mate but they are a must have though.they are a godsend in my environment.i run mine 24/7..55% rh at 3 weeks is okay..

PipeCarver · Jan 19, 2023

Moe.Red said:
The primary issue with higher RH in flower is fungus. Above 60% is tempting fate, but is very strain dependent.

I'd be more worried about that than yield. Proper VPD sets max transpiration, therefore max photosynthesis potential, therefore max flowers. The difference between 60% and 55% may not even be noticeable in your final weight, but mold sure will be.

airflow airflow airflow above below infront behind airflow if you are above 60% 24/7

Madmax · Jan 19, 2023

Moe.Red said:
The primary issue with higher RH in flower is fungus. Above 60% is tempting fate, but is very strain dependent.

I'd be more worried about that than yield. Proper VPD sets max transpiration, therefore max photosynthesis potential, therefore max flowers. The difference between 60% and 55% may not even be noticeable in your final weight, but mold sure will be.

yeah when you in the g spot rh can climb fast..I can watch my dehuey climb a % every second when vpd is on song..it terrifies me.

Ph 007 · Jan 19, 2023

freezeland2 said:
What are the leaf temps? Use leaf temps when calculating your vpd.

Leaf temps very
usually a out 75-78rhey are
When room hits 60+ the go to 79-82f
I was just trying to get rh and temo right hoping that would set my leaf temp

Ph 007 · Jan 19, 2023

Moe.Red said:
The primary issue with higher RH in flower is fungus. Above 60% is tempting fate, but is very strain dependent.

I'd be more worried about that than yield. Proper VPD sets max transpiration, therefore max photosynthesis potential, therefore max flowers. The difference between 60% and 55% may not even be noticeable in your final weight, but mold sure will be.

If after flower at 60-70% aontines 80 in summer I do get some mold some times loose a oz max not bad,

Now u got the option to control the rh a bit better in was wondering is it worth buying £3 a day to run dehumidifier, it gets my rh down to 57-58% from 59-62%
I got good air flor

Ph 007 · Jan 19, 2023

PipeCarver said:
Hi,...I'm in Canada on the east coast with a basement grow. I need to increase my temps to at least 76f higher is better 78f would be better but 76f works...check out my pics if you want. My daytime gets to 76f and night time 65f not ideal but it seems to work.

I need to add moisture when its cold here. my basement now is at around 50% in my flower tent that's great for them......... In my veg closet I add a humidifier to increase to 60 - 65%. I have to add humidity or they don't grow well at all.

The big thing for me is dehue I've 2 - 35 pint and a 30pint in the heat of the summer its 100% humidity here so both are running full blast 24/7 to get the humidity into the 60% range. I try not to flower at that time but shit happens.

Im running day temps 80-82f
The 76f I said was for 1 week at the end, apparently can't protect terpens and then the low th 45%
I'm just trying to perfect final quality not tired this low temo at end yet, my last lot was 80-82f start to finish rh 50-60% last 3 week's was 45-55%

Ph 007 · Jan 19, 2023

Madmax said:
yeah when you in the g spot rh can climb fast..I can watch my dehuey climb a % every second when vpd is on song..it terrifies me.

Same here

I need no extractor fan idel high 24-7 40-50%
And try to keep the heat up And the fan comes in a lot then this keep a my rh 59-62%
Night is fine 52-58%
When I'm at sweet spot for temps my rh can rise quick so I purposely set my heater a tad hotter so fan comes on full most of the time lights on
Rh sits a out 59-60 then No dehumidifier all this is ^

Ph 007 · Jan 19, 2023

Look happy tho
I take air temp readings at canopy level shaded from direct light in that silver box thing in the pics
But
Then the white thermometer in the pic is unshaded the direct led light is hitting it and it's 84f stays 80-84f

And for the record i don't look at leaf temps anymore drive me mad, I'm 1 number away from mental hospital

Rusty74 · Jan 19, 2023

Hi there, sorry if I'm over looking this pal, are you running your extraction full time? Just saying as this can lower rh only if your lung room is obviously at a lower rh, I understand that this will also lower temps in turn needing the heater to activate ££.. what heater are you using? I had a simular issue but luckily for me it was the need to raise rh (humidifier) obviously less costly. I kept my rh more stable and my heating cost down by running my extraction at intervals on a timer...

2Bad · Jan 19, 2023

60-65% humidity is fine with good airflow.. if you don't have that keep the humidity lower..looks like alot of foliage...keep yours lower.

Moshmen · Jan 19, 2023

Moe.Red said:
The primary issue with higher RH in flower is fungus. Above 60% is tempting fate, but is very strain dependent.

I'd be more worried about that than yield. Proper VPD sets max transpiration, therefore max photosynthesis potential, therefore max flowers. The difference between 60% and 55% may not even be noticeable in your final weight, but mold sure will be.

100% this right here

AZsunfarmer · Jan 19, 2023

My experience with high humidity is limited since I live in a desert but I have been making LAB from rice and using an appropriate dose as a foliar spray with some Recharge in veg and early to mid flower. With this and proper airflow do you need to worry as much with high humidity?

Moe.Red · Jan 19, 2023

Let’s forget about the numbers for a minute so you don’t go mental lol.

Are you in the UK? What’s the cleanliness/ natural mold situation in your growspace?

What strain is this? Ever grown it?

Got any other stresses going on?

You planning to defoliate?

Got good air movement?

Growers get away with high rh all the time. It probably is not worth the electricity to fight it too much more than you are unless the result is gonna be botrytis bud rot or PM. If the plant is healthy and at all fungus resistant just get it as low as you can. If you have history with fungus you may need to do better.

Humidity & VPD question, Help Wanted

Humidity & VPD question, Help Wanted

Ph 007

Cirroji

man i'm just a hotdog

Ph 007

Ph 007

freezeland2

PipeCarver

Moe.Red

Madmax

PipeCarver

Madmax

Ph 007

Ph 007

Ph 007

Ph 007

Ph 007

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Rusty74

2Bad

Moshmen

AZsunfarmer

Moe.Red

Humidity & VPD question, Help Wanted

Humidity & VPD question, Help Wanted

Ph 007

Cirroji

man i'm just a hotdog

Ph 007

Ph 007

freezeland2

PipeCarver

Moe.Red

Madmax

PipeCarver

Madmax

Ph 007

Ph 007

Ph 007

Ph 007

Ph 007

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Rusty74

2Bad

Moshmen

AZsunfarmer

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