High RH vs PM/Mold with CO2

[redwhiteblue]

Hey guys,

Interested to see what's working for you when it comes to RH with CO2. I have a monster OG cut that can be pushed really hard.

I'm in the desert with low RH, usually around 30-35, sometimes as low as 15, and when it rains or is foggy it gets up to 50 at the highest.

I run CO2 in all rooms at 1,000ppm, AC is on 24/7 with night temps of 55-65 and day temps of 79-86. All plants are in UC XXL 13s on 40" centers, 40 modules total. Final plant sizes appx 6-7ft including the module, caged.

We run only OG and have never allowed the RH to get above 50%. We have never, ever had one speck of PM or mold in our grows, and we greatly value our bud quality.

I'm interested to know-does anyone have access to any legitimate scientific/aggie research that shows the highest we can let the RH get while preventing PM/mold at all costs? I know the CO2 and higher humidity can be awesome.

Thanks!

 

[Camnibus]

Aren't those more along the lines of air circulation issues?

 

[redwhiteblue]

Aren't those more along the lines of air circulation issues?

I've seen PM and mold in spaces with lots of circulation and ventilation - I've only ever known these two problems to result from high RH. I run 8 ecoplus fans per 200 sqft in my facilities, never had PM or mold, never had the RH over 50 - just want to push the limits with the CO2...

 

[Seamaiden]

If you do some searching on maintaining proper plant sap pH and sufficiently high Brix, you may find what you're after here.

 

[redwhiteblue]

If you do some searching on maintaining proper plant sap pH and sufficiently high Brix, you may find what you're after here.

Haven't found much on the site using google/search function-mostly concerned with finding an RH level to stay under...leaning towards 65.

 

[mmmmmzzzzzz]

Running around 50-60 % RH, then lower towards harvest....

 

[redwhiteblue]

Running around 50-60 % RH, then lower towards harvest....

Yup, exactly what we do.

 

[woodsmaneh]

I use CO2 in my rooms and keep RH around 60%, I have never had PM in my co2 rooms. I let RH ride in the last 10 days or so. I also use RH and Temp controls in all my rooms so things stay the way they should. I would suggest that you up the CO2 to about 1400ppm and keep the rh at 60% to maximize your plant growth potential. RH or Vapor pressure deflect is well worth the read.

Humidity and Vapour Pressure Deficit (VPD)

 

[woodsmaneh]

If you do some searching on maintaining proper plant sap pH and sufficiently high Brix, you may find what you're after here.

I doubt people know what Brix is or how it's used. I have a brix meter that I use every now and than but as a rule I go with Trichromes color's.

 

[altitudefarmer]

VPD is the way to go for sure.
I live in high desert with similar rh. I have seen pm manifest in the range of 20%rh just as much as 70%. IME, a day/night temp difference of less than 8 degrees is the best prevention. I've found fire to be the best cure...lol. I'm sure you've researched many pm cures so I won't waste any more of your time...

 

[redwhiteblue]

I use CO2 in my rooms and keep RH around 60%, I have never had PM in my co2 rooms. I let RH ride in the last 10 days or so. I also use RH and Temp controls in all my rooms so things stay the way they should. I would suggest that you up the CO2 to about 1400ppm and keep the rh at 60% to maximize your plant growth potential. RH or Vapor pressure deflect is well worth the read.

Humidity and Vapour Pressure Deficit (VPD)

Great read, thanks!

 

[redwhiteblue]

VPD is the way to go for sure.
I live in high desert with similar rh. I have seen pm manifest in the range of 20%rh just as much as 70%. IME, a day/night temp difference of less than 8 degrees is the best prevention. I've found fire to be the best cure...lol. I'm sure you've researched many pm cures so I won't waste any more of your time...

What type of humidifiers/controllers do you use?

 

[redwhiteblue]

I doubt people know what Brix is or how it's used. I have a brix meter that I use every now and than but as a rule I go with Trichromes color's.

View attachment 300947

What type of humidifiers and enviro controllers do you recommend?

 

[woodsmaneh]

What type of humidifiers and enviro controllers do you recommend?

I buy sears whole house DH when they go on sale pay about 180$ for them than set them up with an auto fill. I buy the electronic one's they have a 2 year warranty and have returned one in 5 years. I run CAP equipment and have for 10+ years and love the stuff. I use the CAP total greenhouse controllers with CO2 monitors and I am trying out some new CO2 controllers they just released and a new smaller controller. These are older shots when I was doing proof of concept with the humidifiers. Second last is a pix of the controller.

 

[donkeydon]

I use CO2 in my rooms and keep RH around 60%, I have never had PM in my co2 rooms. I let RH ride in the last 10 days or so. I also use RH and Temp controls in all my rooms so things stay the way they should. I would suggest that you up the CO2 to about 1400ppm and keep the rh at 60% to maximize your plant growth potential. RH or Vapor pressure deflect is well worth the read.

Humidity and Vapour Pressure Deficit (VPD) hi woods im building now and what temp humidity conrols would you recommend. thanx bro

 

[woodsmaneh]

I have been using CAP greenhouse controllers ( they were just bought by someone and are reorganizing) and run at 50 to 60% RH and 85 degrees. Currently I'm running at 15000 ppm and 90 to 95 degrees. I don't recommend it as this is some research I'm doing after reading about the effect of higher temps. You heard it here first bro. I have 6 weeks left in this run so should know by the end of the grow if the first time was luck.