hey guys.. im setting up a temporary grow in my garage while i renovate my basement grow area... so there is no a/c in the garage, and here in the south it probably gets about 120+ during the day. i intend to set up my 5x10 tent with 2 1000 watt hps and a 14kbtu portable air conditioner inside the tent. whats the best way to set up the ventilation system? i cant draw constant fresh air from outside the tent b/c it's too hot i was thinking of keeping the tent sealed with a/c inside.. assuming that temp and humidity are kept constant by the a.c. how often and for how long would i want to cycle fresh air into the room?
If you're using a sealed room because exterior air (from the building exterior) is too hot, you could use an icebox chiller setup, which is more efficient than an ac setup and cheaper. Use the icebox to recirculate and draw air through vented hoods, cooling them and transferring the heat into the water. All you have to do then is supplement your grow room with a CO2 source and you don't really need to pull air from outside the grow room. That way you can also use toxic CO2 levels to eliminate any pests (must be sealed room to build toxic levels. should not enter the grow room during this time) and keep a healthy level of CO2 (~1500ppm) for your plants to uptake. One reason that adequate ventilation is important in a grow room is to ensure oxygen and CO2 replacement for continual uptake and increased growth. With a sealed room this can be supplemented much easier than if you had an extraction fan sucking all your supplemental CO2 outside the grow area along with the heat.
One rule I seem to recall on CFM for extraction, you need to find the cubic foot measurements for your grow room, and it should be able to exhaust the room ~3 times per minute. IE: Room is 50cubic feet, then a 150CFM fan should be enough ventilation.