Sealed Room: Optimal Temps, VPD, c02

[epicseeds]

Hello everyone,this is going to be a long one and any brave soul willing to answer any or all of the questions below to the best of their ability will receive my greatest gratitude.

This will be my first sealed room grow with any type of environmental control and am just looking for the best input I can get from a scientific standpoint!

I just got my hands on a nice Environment Controller (Blueprint Controllers Digital Atmosphere Controller with Fuzzy Logic, BDAC-2) The internets grow forums are full of totally contradictory information, and it appears this forum prides itself on the more scientific approach rather than hippy/stoner myth.

A past user here that goes by the name Spurr did a great write up on c02 and how ideally we should be running a sealed room at no more than 1200 ppm. However, he left a few follow up questions unanswered that I was hoping someone could fill me in on.

With that said, I was hoping I could get a general run down from you kind members who have experience in a sealed room with proper environmental settings during flower stage.

Here are my current environmental settings:

DAY TIME FLOWER

• CO2 RANGE: ~1,000-1,200 ppm
• MAX TEMP: 86F
• MIN TEMP: 78F
• MAX RH: 80%
• MIN RH: 70%

Some may see the RH settings and think it is way too high, but I am trying to stay in VPD ranges according to this chart:

What do you guys think of these settings?

• Is it true that c02 is best to be run with higher day time temps - maximum of around 90F?
• What stages during flower is c02 most beneficial i.e. should I lower it dramatically or keep it around the 1200 level during ripening stage?
• With such high RH how can I best avoid bud rot - is there anything else I can do besides giving proper airflow?
• Is there such thing as too much airflow on the canopy?

I have not begun researching proper night settings yet, but here are my thoughts so far.

NIGHT TIME FLOWER

• CO2 RANGE: 0 - 500 ppm
• MAX TEMP: 78F
• MIN TEMP: 68F
• MAX RH: 70%
• MIN RH: 60%

• I have read if you keep night temps a few degrees below day temps the first few weeks it can help reduce stretch - any truth to this?
• If so, how much lower should I keep temps during night once stretch is over?
• Should I run c02 at all during the night?
• Does VPD really matter during lights out? Should I just instead keep RH around the advised 55% instead?

If anyone has any insight in to lights off settings would be much appreciated.

And finally, Spurr mentioned that c02 use can cause ethylene buildup which can adversely effect yield and growth and that it is advisable to fully vent the room once a day. I was thinking ~30 mins after lights go off - thoughts?

Thanks again and I look forward to learning as much as I can here!

 

[mack 10]

Lots of q's.. I'll answer a couple for ya.

Warmer night time temps do indeed mane stockier plants with less gaps between the nodes.
Co2 @ night, no its pointless.
Co2 does indeed work better, 90's works well . You can follow your nutes with c02.
Is, nutes at 1200ppm co2 @ 1200.
Shut off co2 for ripening, it can actually inhibit it a bit.
I like airflow above the canopy.
Vdp works well.
But these many ways to skin a cat.

 

[epicseeds]

Thanks for your input mack 10

I've ran these settings for almost a day now well see how the ladies take them for a few days.

Not sure if my BDAC-2 is faulty but the heating port doesnt seem to be working. Manually running a heater for now.

Only thing I need to do still is cut a hole for exhaust of ethleyne after lights out

 

[epicseeds]

Just an update: Everything is looking good with the above settings. Just so hot and humid to work in the room now lol - I now have to work shirtless

If anyone could offer insight to one thing though about the ethylene.

Is it the plants that produces ethylene after using the c02 or is it only c02 gas burners that produce it?

I was reading this thread and it appears that they came to the conclusion that his c02 gas burner was causing ethylene issues so I am wondering if I even need to vent at night as I am using bottled c02.

Thoughts?

 

[Ogtg2213]

Usually you just vent at night to keep humidity down and save power on the dehumidifyers but it's not necessary to vent at all. Your co2 will skyrocket at night from the plants releasing it but they absorb it an hour after lights on the next day.

 

[brolex]

Hey epicseeds,

I'm dialing my room now for VPD and CO2 setup. Your flowering settings is roughly like my ambient tropical environment 78low/86high with 60%.

Anyway,

I believe those settings in your chart correspond to a "safe" healthy transpiration VPD value of 1±0.2, which is more suitable for vegetative growth. This means at my ambient temp, I still have to crank up the humidifier to bump up my RH to 75%-80%.

However, I am shooting for a flowering (or high transpiration phase) VPD of 1.4 ±0.2, which allows me to turn on my aircon unit which runs dry mode at around 50%RH. Based on VPD of 1.4 ±0.2, I can save power by letting the aircon run dry mode automatically at 75F.

In short, the vege phase is hot and humid, while flowering is warm and reasonably dry.

Fungus spores festers in cold and wet conditions, so I have to avoid temperature drifting too low during the dark cycle.

 

[Douglas.Curtis]

The studies posted in the CO2 thread are referring to seed weight yield decreases. When you read for biomass yield changes, there were no decreases at over 1200ppm CO2.

Now, I'm not a fan of stems and if stems and leaf are all larger at higher CO2 I'll not be interested. Higher or lower CO2 is about quality for me, since yield is veg time and setup related.

 

[SoulAnnoyed]

The studies posted in the CO2 thread are referring to seed weight yield decreases. When you read for biomass yield changes, there were no decreases at over 1200ppm CO2.

Now, I'm not a fan of stems and if stems and leaf are all larger at higher CO2 I'll not be interested. Higher or lower CO2 is about quality for me, since yield is veg time and setup related.

Yall grow some baby assed stems in CO. Never seen such chunked buds on small slithers of stem anywhere else. Sounds like a good thing but never panned out in the smoke. Getting danker the thicker the stems get.. Easier to cure..

 

[Douglas.Curtis]

I'm not from colorado.
Which also has nothing to do with quality.

 

[different]

You might consider referencing another chart.
One that includes leaf temperature as well as ambient.

 

[different]

opennlabs.com/vpd/VPD_calculator.php

 

[Zeez]

Just a guess, but thinking that VDP only applies during lights on when there is transpiration. At night Dew point is the concern when humidity spikes with cooling.











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[Mrkline006]

Would it be worth venting a sealed room @ night for a bit to help keep humidity down?? Also, how do you determine the size of c02 tank you should use? My room will be 9ftx16ft x8ft tall.. Looking to run 1200ppm of c02