Hemp Cultivation


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Author Topic: Just a few questions  (Read 323 times)


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Just a few questions
« Reply #15 on: February 27, 2005, 10:55:49 am »
Penguin, wouldn't turning the air over in a room "several times a minute" make CO2 pretty much impossible to make work?
Sorry if I was unclear in my previous post.
The only reason to exhaust a CO2-enriched environment is for cooling.  In that case you only vent when it gets too hot, and you should set up your CO2 emitter to shut off when the exhaust is running, and you should also only run it when the lights are on.   Environmental controllers are pretty spendy.  If you're going to run CO2, then sealing the environment completely, and using an air conditioner to maintain temperatures (no venting) is definitely something to consider.    
If you're not running CO2, then you should turn over the air as much as possible to keep the CO2 levels up.  4' x 4' = 16 sf x 9'h = 144cf.  Depending on how the ducting is set up, you'd want at least a 300cfm exhaust fan, assuming 1/2 the rated capacity is lost to static pressure, that will turn over the air in the room once per minute.   That's on the low side but the room is very large for the light, so it should work.  
With a 400w HPS, 20green should reduce the grow area to 7sf (for optimal lighting) and maybe reduce the height to 7'.  A properly ducted 150cfm would be perfect for that.
There's a CFM Calculator around here somewhere,  try a search.
Old_Phart is right, you really need to have your environment, techniques, and genetics dialed in perfectly before CO2 will put you on the right side of the cost/benefit equation.