Day Night differential Humidity and Temperature preferences

XtraGood

XtraGood

Well-Known Member
I'm working on dialing in the automation of my flower room before it gets too deep into things, specifically interested in where to set day and night settings for temps and humidity.

1st timer w/ medical permit. Under a variety of LEDs, with OG Kush that seems healthy to me except for where they got away from me a couple times and light levels toasted a few tips. Jacks 321 thru Blumats, 10-15 gal fabric on elevators/drain-platforms, lung room is improving daily (also have in room heating, AC, dehumidification... and a humidifier in storage (we get all the weathers here)).

I have a relay transformer and contactors operated by it that unify my 12/12 lights to one timer; I'm working on how to leg off that to run my nighttime heater and dehumidifier as well. I guess I'd need a "separator" instead of a "contactor", do they make such an animal? Not sure how that'd work; I've got a friend who is more talented with running electrical power than I am, he can likely handle my "separator" issue. I might be better off with heaters and dehumidifiers that have day and night internally, none of mine do at the moment though and I do have an extra heater and dehumidifier...not the worst situation there.

I'm less than certain what my humidity goals should be for day/night? I'm thinking I want it warmer&drier at night and less warm &more humid during the day.

I'm looking at 78f and ~55% humidity as my current target for flower room day and night until I know of better targets, I'll make some wild guesses at them below for your amusement. I got here based on VPD charts, planning on reducing humidity some as flower progresses.

I've seen a lot of posts from @Renfro and others that talk about managing day and night humidity and temperature at separate settings. Warmer nights help plant growth and prevent PM from what I read there. Any other benefits or dangers of different day/night temperature or humidity settings? Seems like I've read that you don't want more than a 10F swing in temp. I might try for 78F/55% daytime and 83F/50% nighttime, but that's just me guessing. More?...Less? Accidentally on target? Help me out here. Thanks!
 
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madvillian420

madvillian420

Well-Known Member
my advice is dont go nuts chasing exact numbers. My setup ran too hot for my last strain but the current strain is loving it. See how they react and adjust from there. Humidity over 65% in late flower can be dicey with microbials, and i wouldnt intentionally push them past say 82f in the day, with a drop, not increase at night. Letting everything cool down 10-15 degrees for that 12 hours of darkness always felt beneficial, IMO.
 
Renfro

Renfro

Well-Known Member
For example 50% humidity at 82F = 80% humidity at 70F. So letting the temperature drop 12 degrees from 82 to 70 caused the RH% to rise 30% with the exact same amount of moisture in the air. At 68F it becomes 85%.
 
XtraGood

XtraGood

Well-Known Member
My current range for temp hi lows (basically day night) is 81-77. I was having some trouble keeping humidity down but I have that handled and it now stays locked at about 53-55%, plan is to go a bit lower humidity once there's some flowers forming.

Thanks everybody, I did forget to say I don't have CO2.

I'll look to avoid large temperature swings that throw the humidity way out of whack.

I read that article TintEastwood, it was dead on point thank you! So DIF (day - night temps = DIF) effects internode length. Greater length for positive, reduced length for negative DIF. Negative DIF also inhibits flower formation because sugars flow to the warmer parts of a plant at night, usually the flowers with positive DIF. Foliage is largely unaffected. There's a lot more worth reading in there too; if all your bookmarks are that good I want that whole list!

I don't really need to increase my internode length and I end up with a slightly cooler night than day time as is so I'll probably just play this round as it lies.
 
TintEastwood

TintEastwood

Well-Known Member
XtraGood said:
My current range for temp hi lows (basically day night) is 81-77. I was having some trouble keeping humidity down but I have that handled and it now stays locked at about 53-55%, plan is to go a bit lower humidity once there's some flowers forming.

Thanks everybody, I did forget to say I don't have CO2.

I'll look to avoid large temperature swings that throw the humidity way out of whack.

I read that article TintEastwood, it was dead on point thank you! So DIF (day - night temps = DIF) effects internode length. Greater length for positive, reduced length for negative DIF. Negative DIF also inhibits flower formation because sugars flow to the warmer parts of a plant at night, usually the flowers with positive DIF. Foliage is largely unaffected. There's a lot more worth reading in there too; if all your bookmarks are that good I want that whole list!

I don't really need to increase my internode length and I end up with a slightly cooler night than day time as is so I'll probably just play this round as it lies.
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Kudos for taking the time.

Another good read on air.


For sure read the section on...

"The night cycle..."

medteknutrients.com.au

CO2 Enriched Hydroponic Growing | Manic Botanix

The CO2 fertilizer effect. Article covers contemporary research about yield increases in under lights growing with CO2 enrichment. Optimum ppm and growth.
medteknutrients.com.au medteknutrients.com.au

Best wishes on all your grows.
 
Ebenezer Kong

Ebenezer Kong

Active Member
Renfro said:
Temperature dropping causes the RH% to spike, so it's best to avoid letting the temps drop unless the RH% is already very low.
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Do you run the same day/night temps and RH%? I’m trying to dial that in. I stopped chasing the VPD dragon after reading some of your past posts on the subject
 
Renfro

Renfro

Well-Known Member
Ebenezer Kong said:
Do you run the same day/night temps and RH%? I’m trying to dial that in. I stopped chasing the VPD dragon after reading some of your past posts on the subject
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Generally the dehumidifiers keep my rooms in the upper 70's during lights out. The temperature doesn't drop too much, that keeps the dehumidifiers more effective as well since warm air dehumidifies easier and since it holds more water the RH% drops. Assuming a static absolute humidity, just warming air will lower the RH% as cooling air will raise RH%. Cooler temps at night are ok so long as RH% isn't getting too high, like during ripening. Cooler temps do slow growth, so I don't like my dark temps to drop too low. Factors vary based on the time of year, day room vs night room... Just not too cool and keep the RH% inline to prevent PM or botrytis.

I have one of the AirROS units on the way, they keep a room sterile (air and all surfaces) so using one it's possible that one could have higher RH% during flower without the risk of botrytis or PM being an issue. This would be sweet as we could actually run VPD without concern. Plus the AirROS unit takes care odor as well. All for less than 30 watts. lol
 
PadawanWarrior

PadawanWarrior

Well-Known Member
Renfro said:
Generally the dehumidifiers keep my rooms in the upper 70's during lights out. The temperature doesn't drop too much, that keeps the dehumidifiers more effective as well since warm air dehumidifies easier and since it holds more water the RH% drops. Assuming a static absolute humidity, just warming air will lower the RH% as cooling air will raise RH%. Cooler temps at night are ok so long as RH% isn't getting too high, like during ripening. Cooler temps do slow growth, so I don't like my dark temps to drop too low. Factors vary based on the time of year, day room vs night room... Just not too cool and keep the RH% inline to prevent PM or botrytis.

I have one of the AirROS units on the way, they keep a room sterile (air and all surfaces) so using one it's possible that one could have higher RH% during flower without the risk of botrytis or PM being an issue. This would be sweet as we could actually run VPD without concern. Plus the AirROS unit takes care odor as well. All for less than 30 watts. lol
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Can I ask what you paid for that AirROS thing? They look pretty nice. I was checking out that post you did the other day.
 
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Ebenezer Kong

Ebenezer Kong

Active Member
Renfro said:
Generally the dehumidifiers keep my rooms in the upper 70's during lights out. The temperature doesn't drop too much, that keeps the dehumidifiers more effective as well since warm air dehumidifies easier and since it holds more water the RH% drops. Assuming a static absolute humidity, just warming air will lower the RH% as cooling air will raise RH%. Cooler temps at night are ok so long as RH% isn't getting too high, like during ripening. Cooler temps do slow growth, so I don't like my dark temps to drop too low. Factors vary based on the time of year, day room vs night room... Just not too cool and keep the RH% inline to prevent PM or botrytis.

I have one of the AirROS units on the way, they keep a room sterile (air and all surfaces) so using one it's possible that one could have higher RH% during flower without the risk of botrytis or PM being an issue. This would be sweet as we could actually run VPD without concern. Plus the AirROS unit takes care odor as well. All for less than 30 watts. lol
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Woa! That sounds pretty slick. Now I know what I’m reading up on tonight! As always, thank you for sharing.
 
PadawanWarrior

PadawanWarrior

Well-Known Member
Renfro said:
The 40XX is a series 4005 (5500 cuft) 4007 (7500 cuft) and so on. 4005 is the smallest.
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I kinda had a feeling that's how it worked, and that's what the XX meant.

If x is equal to 7, what is y, if y=x^2+20?

Just kidding Ren, I wish I could afford one of those suckers. They look sweet. I can't wait to hear reviews.
 
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