Optimal rH level ?

[Dizzy88]

@Aqua Man @AnselAdams ... off to home DEPOT... LOL the one i had was body temp, going to get this IR gun from home depot now.

@Aqua Man @AnselAdams just got the IR gun ... leafs were pulping about 77.5-77.8F about 8-10 inches away from plant ... thats with lights off... so i'm guessing they probably shoot up a bit when the lights flick on??? i will get a reading tonight when lights cycle on for curiosity purposes

current temp conditions: 83F ... 58 rH with 77.8F LST.... what would that put my VPD at?

 

[Dizzy88]

@Aqua Man @AnselAdams just got the IR gun ... leafs were pulping about 77.5-77.8F about 8-10 inches away from plant ... thats with lights off... so i'm guessing they probably shoot up a bit when the lights flick on??? i will get a reading tonight when lights cycle on for curiosity purposes

current temp conditions: 83F ... 58 rH with 77.8F LST.... what would that put my VPD at?

found this link as well:

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

maybe AQUA can double check with his formula if that site's calculator is accurate but i put in my current conditions: 84F - 58 rH with 78 LST... it gave me a 0.97kpa reading for leaf VPD... which would put me within the 0.8-1.1 threshold i think???

 

[Aqua Man]

found this link as well:

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

maybe AQUA can double check with his formula if that site's calculator is accurate but i put in my current conditions: 84F - 58 rH with 78 LST... it gave me a 0.97kpa reading for leaf VPD... which would put me within the 0.8-1.1 threshold i think???

Nvm yup that's right. Leaf temps just lower than I'm used to

 

[Dizzy88]

ok sweet! hmmm so now the time to calculate exactly what i need to do to maintain that 0.8-1.1 with these grow conditions im in.

assuming my temp in tent is around 70-75 at night time (with lights on)... and LST at 75-80 ... i'd need to maintain around 75-80 rH in the tent to be in the acceptable VPD range of 0.8-1.1 for veg stage.... i was sitting thinking i might need a dehumidifier at night, but i think i need to just leave it be.... i'm going to pulp the leaves after about 2 hours of lights on tonight to see what my reading is... i'm really curious now i want to get the best VPD range possible for whatever i'm working with!!

thanks for all the help AQUA and ANSEL.

 

[Aqua Man]

ok sweet! hmmm so now the time to calculate exactly what i need to do to maintain that 0.8-1.1 with these grow conditions im in.

assuming my temp in tent is around 70-75 at night time (with lights on)... and LST at 75-80 ... i'd need to maintain around 75-80 rH in the tent to be in the acceptable VPD range of 0.8-1.1 for veg stage.... i was sitting thinking i might need a dehumidifier at night, but i think i need to just leave it be.... i'm going to pulp the leaves after about 2 hours of lights on tonight to see what my reading is... i'm really curious now i want to get the best VPD range possible for whatever i'm working with!!

thanks for all the help AQUA and ANSEL.

VPD doesn't matter much at night. Plants don't really transpire at night... Only respire so night time humidity of 10-15% lower is ideal to prevent any humidity spike that lead to condensate (hitting the dew point)

 

[AnselAdams]

Nvm yup that's right. Leaf temps just lower than I'm used to

You will want to make changes slowly and then sit back and watch the effects. The pulse makes this very, very easy. Here is the chart for one of my 2x4 tents. It covers 3 days. I did nothing but add water to the humidifier that was preset to 62%. I also use a single T-6 to vent the cabinet. You can actually see the humidifier turning itself on and off. You can also tell when I open the tent to feed, water, etc. The white buttons on the left let you change the display from 1 hr, 3 hr, 24 hr, 1 wk, 1 mth, 3 mth.

i find it just an invaluable tool.

 

[Dizzy88]

VPD doesn't matter much at night. Plants don't really transpire at night... Only respire so night time humidity of 10-15% lower is ideal to prevent any humidity spike that lead to condensate (hitting the dew point)

hope this isnt too stupid of question @Aqua Man but by “night“ are we talking when the lights are off in tent ?

what I meant by night is actual night time here In southern Ontario. Gets so dry when sun sets it goes up to 70-80 outdoors... my plant lights are on thru out the actual nightTime here ... their 6 hour off time is 3-9pm here because its hottest part of day ... my way of trying to combat high temps I guess lol

 

[Aqua Man]

hope this isnt too stupid of question @Aqua Man but by “night“ are we talking when the lights are off in tent ?

what I meant by night is actual night time here In southern Ontario. Gets so dry when sun sets it goes up to 70-80 outdoors... my plant lights are on thru out the actual nightTime here ... their 6 hour off time is 3-9pm here because its hottest part of day ... my way of trying to combat high temps I guess lol

So light on they are photosynthesizing and VPD is important. Lights out they don't really so a lower humidity is fine and actually beneficial in a sense.

 

[Dizzy88]

So light on they are photosynthesizing and VPD is important. Lights out they don't really so a lower humidity is fine and actually beneficial in a sense.

10/4 - makes more sense to me now !

Since my indoor plant lights on during night time here I assume I need to crank my humidifier a bit to run between 10pm to 9am just to get me to that 75-80 rH range becus temps drop and rH spikes outdoors but not enough to get me to the vpd level I need.

during day time I will skate by fine becus temps rise and rH drops a bit but with lights off I have a drop in LST

These are new concepts to me but since my grow temp conditions vary so much I am going to focus on trying to tailor them best I can to achieve best vpd while lights are on. Need to scout n watch like @AnselAdams said and adjust slowly. As always thanks for the priceless knowledge fellas

 

[Dizzy88]

10/4 - makes more sense to me now !

Since my indoor plant lights on during night time here I assume I need to crank my humidifier a bit to run between 10pm to 9am just to get me to that 75-80 rH range becus temps drop and rH spikes outdoors but not enough to get me to the vpd level I need.

during day time I will skate by fine becus temps rise and rH drops a bit but with lights off I have a drop in LST

These are new concepts to me but since my grow temp conditions vary so much I am going to focus on trying to tailor them best I can to achieve best vpd while lights are on. Need to scout n watch like @AnselAdams said and adjust slowly. As always thanks for the priceless knowledge fellas

@Aqua Man @AnselAdams --- well how about this for a mind f*** fellas... LOL... outdoor temps are currently 73F with 67 humidity.

hygrometer sitting on top of my buckets (directly under LED) is reading 85F and 49 rH. the infinity controller (thermostat outside my grow tent, but the sensor i keep it on the floor of the grow tent) is reading 79F and 58 rH. The 2 are always off by 4-5 compared to each reading but i think thats because accu-temp hygrometer is directly under the light and AC infin. sensor probe is on tent floor.

Leaf surface temp is ranging between 79.5-81 on all leaves... light been running for 1.5 hours thus far. if i calculate based on hygrometer im at 1.48kPA leaf VPD ... and if i calculate based on the infinity reading im at 1.54 kPA leaf VPD - either way i think im riding too high... EFFFFF MEEE lol

question... which reading would be the one i go by... the hygrometer directly under the light? also seems like i need more rH in the room either way ... i guess my rH in the tent isn't really mimicking the outdoor humidity durrr lol i feel dumb.

 

[Aqua Man]

@Aqua Man @AnselAdams --- well how about this for a mind f*** fellas... LOL... outdoor temps are currently 73F with 67 humidity.

hygrometer sitting on top of my buckets (directly under LED) is reading 85F and 49 rH. the infinity controller (thermostat outside my grow tent, but the sensor i keep it on the floor of the grow tent) is reading 79F and 58 rH. The 2 are always off by 4-5 compared to each reading but i think thats because accu-temp hygrometer is directly under the light and AC infin. sensor probe is on tent floor.

Leaf surface temp is ranging between 79.5-81 on all leaves... light been running for 1.5 hours thus far. if i calculate based on hygrometer im at 1.48kPA leaf VPD ... and if i calculate based on the infinity reading im at 1.54 kPA leaf VPD - either way i think im riding too high... EFFFFF MEEE lol

question... which reading would be the one i go by... the hygrometer directly under the light? also seems like i need more rH in the room either way ... i guess my rH in the tent isn't really mimicking the outdoor humidity durrr lol i feel dumb.

Teat all equipment for accuracy. You can google how to calibrate a hygrometer with salt and water if you have calibration options

 

[Dizzy88]

Teat all equipment for accuracy. You can google how to calibrate a hygrometer with salt and water if you have calibration options

will calibrate the hygrometer with salt and air tight container tomorrow... personally i think HYGROMETER is off because it wasn't even reading same house temps my thermostat was reading... i know its a variation of .06 on the overall LEAF VPD , but i want them as accurate as possible... either way looks like i need to get my rH to about 75-85 for these babies to get comfortable in the night time ... will keep monitoring and slowly adjust.

edit - by "night time" i mean our bedtime nighttime lol... would still be their "day time" when photo synthesizing. learned alot today! lol

thanks for the help bruv

 

[Dizzy88]

will calibrate the hygrometer with salt and air tight container tomorrow... personally i think HYGROMETER is off because it wasn't even reading same house temps my thermostat was reading... i know its a variation of .06 on the overall LEAF VPD , but i want them as accurate as possible... either way looks like i need to get my rH to about 75-85 for these babies to get comfortable in the night time ... will keep monitoring and slowly adjust.

edit - by "night time" i mean our bedtime nighttime lol... would still be their "day time" when photo synthesizing. learned alot today! lol

thanks for the help bruv

Took another reading this morning before work ... lights running 10 hours now

temp - 74. RH - 71. LST - 73-74

puts my leaf vpd at 0.83 kpa.

Happy with that let’s try to maintain. Kept humidifier on all night cycling off when lights go off.

 

[AnselAdams]

@Aqua Man @AnselAdams --- well how about this for a mind f*** fellas... LOL... outdoor temps are currently 73F with 67 humidity.

hygrometer sitting on top of my buckets (directly under LED) is reading 85F and 49 rH. the infinity controller (thermostat outside my grow tent, but the sensor i keep it on the floor of the grow tent) is reading 79F and 58 rH. The 2 are always off by 4-5 compared to each reading but i think thats because accu-temp hygrometer is directly under the light and AC infin. sensor probe is on tent floor.

Leaf surface temp is ranging between 79.5-81 on all leaves... light been running for 1.5 hours thus far. if i calculate based on hygrometer im at 1.48kPA leaf VPD ... and if i calculate based on the infinity reading im at 1.54 kPA leaf VPD - either way i think im riding too high... EFFFFF MEEE lol

question... which reading would be the one i go by... the hygrometer directly under the light? also seems like i need more rH in the room either way ... i guess my rH in the tent isn't really mimicking the outdoor humidity durrr lol i feel dumb.

Since the most important temp you are concerned with at the plant tops; i would suggest moving the T-6 RH & Temp sensors around the main cola or just a little lower. In the cabinet I use a ty-wrap holder glued to a small magnet to help keep the sensor properly placed with minimum effort In the tent it is ty-wrpped to a light hanger so it can be easily adjusted a the grow proceeds.

 

[Dizzy88]

Since the most important temp you are concerned with at the plant tops; i would suggest moving the T-6 RH & Temp sensors around the main cola or just a little lower. In the cabinet I use a ty-wrap holder glued to a small magnet to help keep the sensor properly placed with minimum effort In the tent it is ty-wrpped to a light hanger so it can be easily adjusted a the grow proceeds.

Love that idea !!! I am going to place the sensor there today ... got the hygrometer in a air tight container with salt today will check after work and make sure it’s calibrated.

I was sitting thinking my tent is mimicking outdoor rH but it definitely isn’t !!!

 

[Dizzy88]

@Aqua Man @AnselAdams Turns out the hygrometer was off by 6 percent. Re calibrating it now ... the infinity temp/rh sensor was most accurate so I sat it on top of the DWC buckets under the lights to get best reading ...After full 18 hour light cycle leafs were at 84-86F surface temp .... probably due to heat temp rise during the day

Temp was 87. RH 53 LST 84-86

I know it’s light off cycle now and shouldn’t worry about Leaf VPD but think I need to kick the humidity up a bit in mornings to combat the rise in temp aqua ? I had it on full blast overnight n water tank emptied so it was doing work...

 

[Aqua Man]

@Aqua Man @AnselAdams Turns out the hygrometer was off by 6 percent. Re calibrating it now ... the infinity temp/rh sensor was most accurate so I sat it on top of the DWC buckets under the lights to get best reading ...After full 18 hour light cycle leafs were at 84-86F surface temp .... probably due to heat temp rise during the day

Temp was 87. RH 53 LST 84-86

I know it’s light off cycle now and shouldn’t worry about Leaf VPD but think I need to kick the humidity up a bit in mornings to combat the rise in temp aqua ? I had it on full blast overnight n water tank emptied so it was doing work...

Personally I only spot check around the plants for microclimates. All my testing equipment is out of the light about canopy height or close to middle of the room. If you have good circulation it's imo the most accurate and if you have an issue then you know it's circulation related.

To get leaf temps down there are some things you can do. Lower the temp of the media. As the plants take up cooler water it will aid in lowering leaf temps. Can toss a frozen water bottle in the res. Freeze a few and just rotate them I suggest the bigger the better so your not having to change then all the time.

Stick to the high side of VPD this will increase transpiration rates and create more evaporative cooling. May need to lower the ppm of the solution to make up for more uptake.

Add a little more circulation this will also increase evaporative cooling creating forced evaporation. But be careful not to much. An oscillating fan that makes the leave just wiggle a little as it passes will help.

 

[Dizzy88]

Personally I only spot check around the plants for microclimates. All my testing equipment is out of the light about canopy height or close to middle of the room. If you have good circulation it's imo the most accurate and if you have an issue then you know it's circulation related.

To get leaf temps down there are some things you can do. Lower the temp of the media. As the plants take up cooler water it will aid in lowering leaf temps. Can toss a frozen water bottle in the res. Freeze a few and just rotate them I suggest the bigger the better so your not having to change then all the time.

Stick to the high side of VPD this will increase transpiration rates and create more evaporative cooling. May need to lower the ppm of the solution to make up for more uptake.

Add a little more circulation this will also increase evaporative cooling creating forced evaporation. But be careful not to much. An oscillating fan that makes the leave just wiggle a little as it passes will help.

Yes I was going to ask ya if water Rez temp spiking can cause leaf surface temp to rise .... I put a Frozen bottle of water in each Rez after work everyday for about 30 mins seems to cool it down. Should I be putting more than one each time ??? Maybe someone has experience with that in 5 gallon DWC buckets

I got the mini fan blowing over The plants 24-7 and another tower fan oscillating the room 24/7. Is it overkill if I add one more oscillating fan to the mix ... that’ll make it 3 rolling 24/7?

Going to check ph/ppm shortly but been keeping them hovering at 400-450.

 

[Aqua Man]

Yes I was going to ask ya if water Rez temp spiking can cause leaf surface temp to rise .... I put a Frozen bottle of water in each Rez after work everyday for about 30 mins seems to cool it down. Should I be putting more than one each time ??? Maybe someone has experience with that in 5 gallon DWC buckets

I got the mini fan blowing over The plants 24-7 and another tower fan oscillating the room 24/7. Is it overkill if I add one more oscillating fan to the mix ... that’ll make it 3 rolling 24/7?

Going to check ph/ppm shortly but been keeping them hovering at 400-450.

Sounds good. Wind during light out can be much lower the plants don't transpire much and so you don't get that benefit from increased evaporative cooling.

 

[Dizzy88]

Sounds good. Wind during light out can be much lower the plants don't transpire much and so you don't get that benefit from increased evaporative cooling.

10-4 . i am going to get one more timer... will set the 3rd fan on to cycle on/off with the light cycle...have one kicking around just didn't want to use it thinking it'd be overkill lol...appreciate all of the help as always AQUA. im curious to see what my reading for LST will be after lights off for 1-2 hours.