Please Help! Exhaust during Dark Hours? Wasting Co2

sooooooo today when picking up some new soil, FFOF, i heard this today and since i am starting a new grow i wanted some input from some pros....

is it ok to turn off my fans/exhaust ventilation during the dark cycle? i was told from the dude at the grow store that plants give out co2 at night and it is perfectly fine leave the fans off and infact its a waste of good co2 if you dont....any truth here? experts please respond! +rep

I run mine 24/7 for odor controll, unless you are running a c02 gen then run it.

thats the point tho, it was told to me that plants give off co2 at night while they are transpiring...so should i really keep the exhaust running?

from ask.com

At night plants give off carbon dioxide as a byproduct of the process of respiration, no photosynthesis occurs at night because of no sunlight. In day time they take in carbon dioxide and give off oxygen for the process of photosynthesis. respiration also occurs in day time and carbon dioxide is released but is again used for photosynthesis so no carbon dioxide is released in day time.

This might be true but odor control is 100% better that some c02 eitherway you answered you ? And you have to choises
To make.

Unless you run a dehumidifier during lights out, you should leave your extract on. Humidity rises during the dark period, which in turn can lead to problems with mold, fungus and bud rot.

Nocturn3 said:

Unless you run a dehumidifier during lights out, you should leave your extract on. Humidity rises during the dark period, which in turn can lead to problems with mold, fungus and bud rot.

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Yes i agree 100%

is there such thing as too much exhaust then? i am running a 400 cfm fan inside of a 5x5 tent....am i changing the air to frequently?

anyone on here ever try turning off the exhaust at night? vs not doing it? thanks!

Your humidity will likely sky rocket to 70%+ with no ventilation/exhaust during lights out, mine did. I run 2 hoods in a 4x4 tent with a 435cfm fan (for a mere 6 flowering plants). 79f/30%rh lights on and 67f/40%rh with lights off and exhaust on. The first night I tried putting my exhaust on a timer (to shut off 1 hour after lights off and on 1 hour before) the humidity shot to almost 70% within 3 hours of lights out. I quickly went down and flipped the bypass for the exhaust timer so it runs 24/0 at 85 - 90% on the variable speed controller.

ic, thanks a lot guys! i guess i will keep the ventilation on 24/7....next question is for my 5x5x7 tent do i really need the power behind my 400cfm or should i just use my 150 cfm cheapo home depot duct fan? is there such thing as tii much ventilation/fresh air?

No the more the better

solarguy said:

sooooooo today when picking up some new soil, FFOF, i heard this today and since i am starting a new grow i wanted some input from some pros....

is it ok to turn off my fans/exhaust ventilation during the dark cycle? i was told from the dude at the grow store that plants give out co2 at night and it is perfectly fine leave the fans off and infact its a waste of good co2 if you dont....any truth here? experts please respond! +rep

Click to expand...

...I use a co2 burner w/ monitor set at 1500ppm. My monitor has a light sensor that turns the co2 on when my lights come on. Your ladies use co2 when they are photosynthesizing, not when they sleep....I do not exaust my room while lights on, I simply run a carbon scrubber reversed. However, I do exaust my room during lights off. High humidity during lights off can cause mildew/mold/bad fungi/bad bacteria....just don't do it.

solarguy said:

ic, thanks a lot guys! i guess i will keep the ventilation on 24/7....next question is for my 5x5x7 tent do i really need the power behind my 400cfm or should i just use my 150 cfm cheapo home depot duct fan? is there such thing as tii much ventilation/fresh air?

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Variable Speed Controller = ~$25

I keep a remote temp/humidity gauge in my tent an inch or two above my canopy and tailor my fan to my temps. In the winter I was running at 65 - 75% power but now spring is here and I dialed it up to near 90% to keep my temps below 80.

*This is what I got from my local grow shop.

http://www.google.com/products/catalog?hl=en&rlz=1C1CHFX_enUS425US425&q=variable+speed+controller&bav=on.2,or.r_gc.r_pw.&biw=1134&bih=914&um=1&ie=UTF-8&cid=13177389898028996549&sa=X&ei=mGXJTYe7OKPY0QGxy53-Bw&ved=0CJkBEPMCMAI#

trichome fiend said:

...I use a co2 burner w/ monitor set at 1500ppm. My monitor has a light sensor that turns the co2 on when my lights come on. Your ladies use co2 when they are photosynthesizing, not when they sleep....I do not exaust my room while lights on, I simply run a carbon scrubber reversed. However, I do exaust my room during lights off. High humidity during lights off can cause mildew/mold/bad fungi/bad bacteria....just don't do it.

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how do you keep the room cool without exhausting?

I have to say it really comes down to your whole room set up, cause I turn my exhaust off at night when lights go out an I never get humidity above 40 percent. I am running a 600 w with a 6 inch reflector pulling with a 400cfm fan. My room size is 4x7x6 and i also can keep my lights less than a foot of my plants with no problem. Also I run waterfarms and I have a tote of water hanging out in the corner. I am no pro by any means but I can only say what my set up has and its way different results than anyone posting here so far

rasputin71 said:

Variable Speed Controller = ~$25

I keep a remote temp/humidity gauge in my tent an inch or two above my canopy and tailor my fan to my temps. In the winter I was running at 65 - 75% power but now spring is here and I dialed it up to near 90% to keep my temps below 80.


*This is what I got from my local grow shop.

http://www.google.com/products/catalog?hl=en&rlz=1C1CHFX_enUS425US425&q=variable+speed+controller&bav=on.2,or.r_gc.r_pw.&biw=1134&bih=914&um=1&ie=UTF-8&cid=13177389898028996549&sa=X&ei=mGXJTYe7OKPY0QGxy53-Bw&ved=0CJkBEPMCMAI#

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do they make an automatic one?

also i dont get the idea of not running exhaust and bringing in new air, why would you turn it off even if your temp was fine

solarguy said:

how do you keep the room cool without exhausting?

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...I have a double hose a/c unit that recirculates the same air, keeping co2 in room.

trichome fiend said:

...I have a double hose a/c unit that recirculates the same air, keeping co2 in room.

Click to expand...

how big is your room? the ac doesnt bring air in and out of the room? what kind of unit and is it expensive to run?

joe dollar said:

I have to say it really comes down to your whole room set up, cause I turn my exhaust off at night when lights go out an I never get humidity above 40 percent. I am running a 600 w with a 6 inch reflector pulling with a 400cfm fan. My room size is 4x7x6 and i also can keep my lights less than a foot of my plants with no problem. Also I run waterfarms and I have a tote of water hanging out in the corner. I am no pro by any means but I can only say what my set up has and its way different results than anyone posting here so far

Click to expand...

do you have ac?

A perfect room is a non vented room, this being said its going to cost more that just going with
A in and out to control heat and odor. Things you will need to go sealed 1# a Ac unit 2# dehumidifier
3# c02 gen 4# coool tubes 5# a c02 monitor 6# a good scrubber, these are the basics of what you
Are going to need to go sealed