Venting for cooling or Fresh air?

[Heyoka23]

As a newb, the most confusing aspect of setting up a grow that I have come across is ventilation. 3 times a minute, once every five minutes, timers, speed controlers, blah blah blah. I'm confused.

I'm building an 8x4x7 room that will have two air cooled hoods with 600 watt lights in them. The air will be pulled from a crawl space beneath a trailer and returned there via a 340 cfm sunlight supply inline fan. I will be using insulated duct. I'll also have a 6300 btu window ac unit in there.

So...correct me if I'm wrong but I believe that in considering proper exhaust for the room my primary concern will not be cooling but will be providing fresh air for the plants to breath properly. If that is the case what kind of air flow should I shoot for?

Is it possible to provide too much air flow?

What about winter time and 30 degree outside air? How important is getting air from outside to the plants?

 

[trichrider]

ventilation is adequate with 340 cfm pulling out of a bit over 200cf in your room.
if you have an ac in there point it at the ceiling...

now i'm confused...is the lamp ducted? or contributing to the temps?

 

[Heyoka23]

The plan for the lights is to use the 340 cfm fan in a sort of closed loop. The fan will pull air from a hole in the floor and run it through the lights (yes, ducted hoods) and then back through another hole in the floor.

Fresh air and odor control will be done via a moded lasko blower and a passive intake that will be hooked via vent pipe to another hole in the floor. The fan will pull the air through the carbon filter and exhaust it outside of the room into another room.

I've seen charts used to determine proper airflow and they all seem to be going for temperature drops. The fan that I'll be using to exhaust the room (the lasko) is said to move about 265 cfm but it also has two lower settings.

I guess the first thing I'm wondering is how much air needs to be exhausted to maintain co2 levels equal to what the plants would experience outside.

I'm also wondering if it's safe to move cold winter air through the lights or could it damage them? I know that I don't want to be pulling cold winter air into the grow room as it will hurt the plants.

The room is still under construction so perhaps I should just AC the room in which the grow room will reside?

 

[Neo 420]

The plan for the lights is to use the 340 cfm fan in a sort of closed loop. The fan will pull air from a hole in the floor and run it through the lights (yes, ducted hoods) and then back through another hole in the floor.

Good...

Fresh air and odor control will be done via a moded lasko blower and a passive intake that will be hooked via vent pipe to another hole in the floor. The fan will pull the air through the carbon filter and exhaust it outside of the room into another room.

Not following here...
You stated you have a window ac unit. Some waste would be going on with your current plan.
If the room is sealed, running a closed loop system for lights and AC'd, just run the scrubber in the room on the fan. Make sure the fan/ scrubber system is slightly over rated for the room. No need for all them other holes and thing-a-ma-jigs.

I've seen charts used to determine proper airflow and they all seem to be going for temperature drops. The fan that I'll be using to exhaust the room (the lasko) is said to move about 265 cfm but it also has two lower settings.

Dial in the AC, some oscillating fans and you'll have proper airflow and temps.

I guess the first thing I'm wondering is how much air needs to be exhausted to maintain co2 levels equal to what the plants would experience outside.

Get a CO2 tank. (or whatever CO2 emitting device you choose but tank has no heat and cheap to refill) use a CO2 device to monitor and distribute the proper CO2 amount (1000 to 1500ppm) or use timer to control (example - On 5min off 45min every hour while lights on- Off completely when lights off )