Humidity and Temperature

[Chronic100]

Hi,

Today I bought a oil rad as my temperatures were getting too low in my tent. I am growing an Auto Northern lights and Auto Blueberry.

I also have a automatic humdifier, and before getting the oil rad I would set the humidfier to 65% (as my plants are in their second week of growing) and it would stay at that humidity.

Now I have the oil radiator, I am only able to keep the humidity as high as 45-50%.

Is this a problem? I'm am 2 days into my second week so far and after installing the rad today I can't get the humidity any higher.

I would really appreciate any help, or advice.

Many Thanks.

 

[AutoWonders]

I'm lucky if I can get even 60% humidity when my evaporative cooler runs during summers. Low humidity I do find to be very problematic.
You could consider something I have done for a long time. I have my radiator heater in an old two drawer file cabinet pushed up to my lower tent screen and the inline fan sucks the heat in for the warm and toasties.

 

[Olderfart]

VPD charts are your friend...

Here is one that I use. This one assumes that leaves (due to evaporation) are 2C cooler than the air. Others assume other differences. Bottom line is that plants react to the combination of temperature and humidity, not just one or the other. A different air temperature means a different optimal humidity. For example, on this chart, 50% RH is near ideal at 23C but bad news too dry at 30C.

Happy growing.

 

[tip]

You have to be careful but you can soak a clean towel with water, wring it out a little so it doesn't drip, and hang it on an inside wall of the tent. In a 4x4x7 tent you can raise RH by about 5% with the lights on but I'd remove it when the lights are off. Wet things can assist fungus growth in a dark cool environment.

 

[Simplicio]

Here is an Easy to Read VPD that i use
View attachment 1190649

Modifying a VPD chart changes it into something that isn't a VPD chart.
The truth is most cannabis growers abandon the VPD chart during flower because of fear of bud rot.
Some of us continue using a real VPD chart til harvest, and never get bud rot.
At least that's the case with me in hydro.

 

[Death The Cultivator]

Vapor Pressure Deficit VPD Calculator - Dimlux Lighting - The Best Grow Lights

Vapor Pressure DeficitCalculator Calculate both Room VPD and Leaf VPD automatically Just enter the value below to generate the VPD values for your room and your plants. You’ll need to know the room’s temperature, relative humidity, and the plant’s temperature. We recommend calibrating your...

www.dimluxlighting.com

Modifying a VPD chart changes it into something that isn't a VPD chart.
The truth is most cannabis growers abandon the VPD chart during flower because of fear of bud rot.
Some of us continue using a real VPD chart til harvest, and never get bud rot.
At least that's the case with me in hydro.

I do the same. Temps run around 85f in the attic so I run higher humidity but no mold. I think using a temperature gun on the leaf surface gives a more accurate idea.

 

[Diamond Dog Hair]

Modifying a VPD chart changes it into something that isn't a VPD chart.
The truth is most cannabis growers abandon the VPD chart during flower because of fear of bud rot.
Some of us continue using a real VPD chart til harvest, and never get bud rot.
At least that's the case with me in hydro.

Thanks for bringing up the flaw in the chart i am using. After cross referencing it to a full VPD chart, the one i am going off of for flower is wrong. I thank you and my plants thank you. I gotta go adjust my inkbird.

 

[Mir]

Vapor Pressure Deficit VPD Calculator - Dimlux Lighting - The Best Grow Lights

Vapor Pressure DeficitCalculator Calculate both Room VPD and Leaf VPD automatically Just enter the value below to generate the VPD values for your room and your plants. You’ll need to know the room’s temperature, relative humidity, and the plant’s temperature. We recommend calibrating your...

www.dimluxlighting.com

I do the same. Temps run around 85f in the attic so I run higher humidity but no mold. I think using a temperature gun on the leaf surface gives a more accurate idea.

I grew two CDLC in my 32x32 a few months ago with temperatures between 75° and 80° and RH as high as 77%, and it was never lower than 60%. Neither mildew nor bud rot reared their filthy heads. It was quite the pleasant surprise, given the constant refrain of never having RH go above 50% in late flower.