What Range Should I Maintain For My Growroom Humidity & Temperature?

[AdaminCO]

Take a peep at what I found today.
You do have to take in count lights that have IR and UV.

Those times you find valuable information

There is a prevailing consensus that 75 °F is the ideal ambient temperature to grow Cannabis under HPS lighting without CO2 supplementation. This Experiment result indicates that an 84 °F ambient air temperature is required to achieve the same optimal leaf surface temperatures when using...

www.420magazine.com

 

[Buds Buddy]

Another thing I've found true about LED's is, if you put them too close to the leaves you will start getting Calcium spotted leaves.

 

[straightup]

The leaf temperature would be controlled by how high you hang your light. Closer it is the warmer your leaf temp. As far as the grow area being heated warmer .... never heard that before. Just a low temp of 68 F lights out & a high of 84 lights on to be in a good growing range with 77 F being the target temp. Been shooting for 77 F for 3 years now with MH, HPS, Fluorescent, Bluple LED & White LED. Tried all these lights & always went for 77 F.
That light company is the only one I've ever heard make that statement even. They are some top of the line lights. Maybe they know something other light companies don't.
Either way, I'll stick to the 77 F that I know works well.

The link at the end of the post that I quoted has an abstract that shows the results of their tests on several different plant types, including cannabis, using a FLIR gun. Obviously it's impossible to know how controlled their experiments actually were, but I'm not seeing any issues in what their premise states - which is that full spectrum LEDs do not produce excess infrared nor any other unusable light that HPS and MH lamps do, meaning the leaf is not being subject to the heat that the aforementioned light systems (HPS MH) produce. If we agree that the leaf's optimal surface temperature is ~86F for various metabolic reactions to occur, then it is necessary to raise the ambient temperatures approx. 9 F to make up for the LED's more efficient use of the light spectrum.

77F ambient in a HPS grow should be damn near optimal for LST. But if you are running LED's, you will need to raise your ambient temps to somewhere around 84 - 86 F.

I encourage you to take a look at the paper I linked and if nothing else check out the graphs they made comparing the surface temps of various lighting setups.

 

[CannaFish]

warm temps sound great for vegetive growth, but what it is the optimal leaf surface temperatures during flower? Specifically what temps will produce maximum thc and preserve the terpenes? I've read somebody on here talk about not going over 80 degrees F, but I'd like to learn some more specifics about getting the most out of the available terpenes. I have a Haze that smells different depending who and where it's grown.

check out this article...

The Quest to Grow the World's Most Powerful Pot

A Denver grower who goes by RB-26 claims to have achieved the first strain to consistently test at 33 percent THC. That's some STRONG weed.

www.vice.com

"It's also easier to control factors like temperature and humidity in these smaller environments. RB-26 maintains a lower overall temperature than most growers—72 to 77 degrees as opposed to high 70s or low 80s. "Heat is one of the biggest stressors of plants and as your temperature rises, you're going to be degrading terpenes [aromatic plant compounds] and oil production, and that directly affects potency,""

 

[CannaFish]

Here is my take. I keep my room at 68-72 degrees and humidity at 55%. I do this cheaply. Here is how. I have a lot of ac/heat knowledge, was in that business at one time. You get on your Facebook market , Craig’s list , garage sales. People are always getting rid of humidifiers and dehumidifiers that have settings. Usually they heat the air mist or dry heat. You set the dehumidifier at 55 and the humidifier at 60. For temp control, you might have to find someone to do this if you don’t know how. Get one of those hotel combo heat and air units. A 110 volt thermostat. Wire it where it has a range of 5-7 , do that so it does not constant run on heat or ac fighting itself .set it at 70. Get yourself a 6 inch inline with filter and stat on it. Remember that air in your house has a higher CO2 than outside air. I don’t use CO2. I find it a waste. I am cheap, like to save money. Been at this since the 70’s in Newton County Arkansas. For those of you young guys that use to be known as the place to get the best for a long time. I won’t get into much of that. I am here to soak in what others know and learn, and to share my own experience. Appreciate feedback. I also now use led, use about 4500 watts in 50 sq ft space.

excellent info. thanks for sharing your knowledge.

 

[AdaminCO]

warm temps sound great for vegetive growth, but what it is the optimal leaf surface temperatures during flower? Specifically what temps will produce maximum thc and preserve the terpenes? I've read somebody on here talk about not going over 80 degrees F, but I'd like to learn some more specifics about getting the most out of the available terpenes. I have a Haze that smells different depending who and where it's grown.

check out this article...

The Quest to Grow the World's Most Powerful Pot

A Denver grower who goes by RB-26 claims to have achieved the first strain to consistently test at 33 percent THC. That's some STRONG weed.

www.vice.com

"It's also easier to control factors like temperature and humidity in these smaller environments. RB-26 maintains a lower overall temperature than most growers—72 to 77 degrees as opposed to high 70s or low 80s. "Heat is one of the biggest stressors of plants and as your temperature rises, you're going to be degrading terpenes [aromatic plant compounds] and oil production, and that directly affects potency,""

0C620228-3FC4-4CC2-BB1B-0AE0747582CC.png

• AdaminCO
• Aug 21, 2019

Vpd

RH is just as important as temp. These are two charts I use for reference.

75 degree leaf temp is optimal.

 

[CannaFish]

Thanks for sharing the VPD charts! I like that 2nd one.

 

[TorturedSoul]

warm temps sound great for vegetive growth, but what it is the optimal leaf surface temperatures during flower?

It depends somewhat on strain choice, of course - as "cannabis" isn't a single, generic object like (for example) pure water is. But it also depends on the amount of light-energy the plant is receiving and the CO₂ level. Therefore, there is no simple answer. That 88.6°F (IIRC) temperature that gets mentioned occasionally assumes normal ambient CO₂ level and the maximum light-energy that the plant is capable of processing under that atmospheric condition. Again, somewhat strain-dependent.

Also, various factors may influence the maximum temperature that a cannabis plant can tolerate. A cannabis plant being grown in a large DWC reservoir that is very highly (and constantly) oxygenated, and that has a more or less constant high flow of fresh air to aid/facilitate transpiration will generally be capable of tolerating significantly higher temperatures - and will likely continue to thrive even when an identical plant placed in the ground outdoors in similar temperatures would experience periods when there is "not much going on" in terms of development. But even that outdoor in-ground plant will tolerate higher temperatures if it has a good root system that allows it access to adequate moisture and, again, is able to maintain a high rate of transpiration. Among other things that transpiration does is to enable a plant to self-cool.

 

[straightup]

0C620228-3FC4-4CC2-BB1B-0AE0747582CC.png

• AdaminCO
• Aug 21, 2019

Vpd

RH is just as important as temp. These are two charts I use for reference.

75 degree leaf temp is optimal.

While there are some fluctuations to optimal LST, depending on strain, there was a university study conducted a couple years ago on optimal LST for cannabis. The conclusion was that 25 - 35 C was considered optimal for photosynthesis to occur. That would be 77 to 95 F. I've seen other more informal studies that have narrowed that number down to somewhere around 85-86 F as being optimal for LST. This is assuming that your humidity is 65-75%.

 

[AdaminCO]

I found a very good study, but they deleted the link.
It all depends on your type of lighting. Ambient differs light to light. (Spectrum)

 

[CannaFish]

I found a very good study, but they deleted the link.
It all depends on your type of lighting. Ambient differs light to light. (Spectrum)

I did see a thread on icm that showed similar photos to the one you posted but it was LED vs HPS . It clearly showed the hps plant had higher LST than the LED plant at the same ambient temps.

I researched a little more about that grower RB26 I posted the link about above. Some one asked for some grow tips, he responded...

“ I'd follow the VPD chart for atmospheric conditions if you are new to growing. A simple Google search will bring up the image for you.

I use 1000W Gavita E-Series fixtures in commercial voltage - so the electrical draw will be different than what you're using. I believe the the 240V Gavita's pull 4.5A at 1000W.

I utilize coco in a drain to waste, multifeed application.

My plants are always topped, at least 2 times. Generally each plant is paired with a 54" tomato cage but these days I've been experimenting more and more with trellising with great results.

I've experimented with all the bottled nutrients from the hydro store and had best results with a mixture of Botanicare and with a couple Advanced Nutrients flowering additives. This past year I've been using raw agricultural salts and making my own nutrients however. This has gotten the cost down to about $.02/gallon.

There are lots of products that can help promote healthy plants. I'd look into silica additives and beneficial enzymes. Be wary of what you find off the shelf at hydro stores though - many of those products are just designed to take your money.

Happy Growing!”

 

[straightup]

I did see a thread on icm that showed similar photos to the one you posted but it was LED vs HPS . It clearly showed the hps plant had higher LST than the LED plant at the same ambient temps.

I researched a little more about that grower RB26 I posted the link about above. Some one asked for some grow tips, he responded...

“ I'd follow the VPD chart for atmospheric conditions if you are new to growing. A simple Google search will bring up the image for you.

I use 1000W Gavita E-Series fixtures in commercial voltage - so the electrical draw will be different than what you're using. I believe the the 240V Gavita's pull 4.5A at 1000W.

I utilize coco in a drain to waste, multifeed application.

My plants are always topped, at least 2 times. Generally each plant is paired with a 54" tomato cage but these days I've been experimenting more and more with trellising with great results.

I've experimented with all the bottled nutrients from the hydro store and had best results with a mixture of Botanicare and with a couple Advanced Nutrients flowering additives. This past year I've been using raw agricultural salts and making my own nutrients however. This has gotten the cost down to about $.02/gallon.

There are lots of products that can help promote healthy plants. I'd look into silica additives and beneficial enzymes. Be wary of what you find off the shelf at hydro stores though - many of those products are just designed to take your money.

Happy Growing!”

Hello CannaFish,

Here's the link to the study that was conducted by Black Dog about LST. If you don't want to read it - just check out the graphs they posted.

HPS vs LED Leaf Temp

 

[Growdad420]

I am doing my 5th flower cycle. I have a 4'4" square by 7.5 feet tall flower area. a 600 W HPS light over head and 400W of fluorescent CFLs and T5 panels surround the plants for all over lighting. My temps get up to 82 degrees in day time with 40% humidity during veg and 85 degrees and 30& humidity during flower. I grow 9 plants at a time in soil and use a basic 3 part nutrient solution. Yield between 12-24 oz per flower cycle. Use root organics formula 707 and advanced hydroponics beginner basic nutes.

Everything I say is imaginary and simply for role playing purposes only.

lets see some pics!

 

[Growdad420]

Try soda bottles filled with water in the freezer and they turn in the blox of ice and then you can sit them in your grow tent and have the fans blow over them to blow cool air on to your plants and the temperature in your grow tent will gradually lower ( depending on 10 size and how many blocks of ice you use oh and by the way you might want to sit the soda bottles in a container to catch the drip from the bottle as the ice melts)

This is a great suggestion!

 

[Elvin]

I grow on the second story of an old farm house that has no heat nor air conditioning up there. The ancient furnace was needing to be fixed for the 6th year in the row, with the prior year being the pilot light (that I had to buy used parts to fix it because new ones were not available) so instead of fixing the 40-year-old thing so I went to 99.8% efficient radiant heat and a window air conditioner. It also meant my upstairs forced air vents were useless hence the no heat, no air conditioning. My propane bill is 60% less and the electric bill is $100 less for the air conditioning now BTW so I'm very happy.

What I do to cool my tents up there in that sweat-inducing second floor in the summer is run a 6-inch flexible intake duct from my fan down to the first floor and repurposed the old 16X20 furnace cold air vent into a filter box for that. I do put a couple of bag of dog food in front of the vent (it's on the kitchen wall so a piece of cardboard would look even tackier instead of DF stored under the kitchen table) so the fan does not pull too much cool air (and heat up the first floor) but that upstairs can be almost a 100°F but the tents (exhaust of one is the intake of the other) are nice and cool below 80°. I also have my QB transformers outside the tents to keep temps down.

My suggestion for cooling is a long intake duct for your fan sucking cold air from a cooler room. Or even better find a room vent blowing cold air, take the grill off, and squeeze the ducting to fit in the vent (use old socks or something to block any air leaks) if you are too scared of the wife to take the vent out and directly connect the 2 ducts up.
With multiple tents just connect them up in series and increase the fan speed if needed.
They'll blow up like balloons but as long as you stay careful with the zipper, those big zipper teeth can take the added stress easily.

 

[TorturedSoul]

Sourcing air from a cooler part of the house - or outside, if it's cooler out there - instead of constantly recirculating air between a grow tent and the room it's located in, and expecting it to not lead to problems...seems like common sense.

There's a thread around here somewhere in which someone stated they stuck a grow tent into a closet that wasn't all that much bigger than the tent - and found they were experiencing issues with high temperatures. My first thought was, "What universe are you from, where the physical laws of reality are so much different than ours that you ever expected anything else?" lol. Maybe common sense... should be renamed .

 

[OGeMann]

when dealing with Humidity and Temperature get a controller that controls hum/temp they do come in handy

 

[1st Maximus]

Woodsmans Mazar Bud Shot:

Very nice

 

[Odjob]

I run a high transporation rate, with leaf surface temps in the high 70's low 80's. Air movement in my room is gental so heat can do the job. It's almost endless the things that effect that.

 

[Odjob]

Soil temperature is one of them.