Anyone have experience cutting own vent hole in tent? I need to run air conditioner vent tube through tent and no vents exist in that area. What’s best way to cut and be able to seal around vend hole? Thanks
I’ve never done it, but I’ve thought something like this for under $20, or even a simpler version, if I ever did. Cut an X, slip it through, and screw/bolt it to a plywood square, or a couple of 1x2 slats on the other side. A 6" might be tougher to find something applicable, maybe a stovepipe fitting of some kind, but lots of options for common 4" appliance ducting…
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Good idea 
Bubbala.
What do you have vents and what is currently filling them? Ideally you would want to bring ac in bottom and there is usually at lest one duct vent and a passive intake?
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Yes there is but on opposite end of tent. I need to be close to a window to exhaust my AC and tent vent is way to high on that end of tent. I would have lots of vent hose going around with lots of twist and turns. Thanks dbrn32.
How big of hole do I need to leave at bottom of tent to allow fresh air in.? I got a 5’ x4’ 80” tall tent
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Depends on how much air exhaust fan is moving. You want negative pressure inside of tent if using a filter, but not so much it will cause your tent to rip or tear.
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Circle cutter for paper should get through a tent with a couple or three passes.
You can make a swing-gauge to test for flow & losses, dial in your intake area, etc.
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If I set fan speed and close bottom vent till tent starts to cave a bit would this be ok ?
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In most cases, but every grow room is a little different. The purpose of exhaust is to expell heat and introduce co2. As long as you’re doing this to reasonable amounts your setup should be good.
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Look up Secrete Jardin DF16 Light Baffle with Mesh its around 10-15 dollars and allows you to cut out a hole perfectly and replace with a mesh light baffle
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Thanks dbrn32. Appreciate that 
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Thanks LiesGrows will have a look at this.
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Ive personally never used one myself but ive seen them used in videos and is a nice way impo of putting in a port thats not typically there!
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Awesome knowledge share, thanks.
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Thanks you much!! Problem was revealed at a very sacred moment in last night’s thought gathering process. 
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Probably less accurate than working with a diy swing gauge, but it should still put you close to max cfm for your exhaust fan (minus any losses from any filters, tubing etc that the exhaust fan is seeing) while still leaving some negative pressure in the tent, which is good because it will leave some velocity on the intake air. Too much intake area & the intake air gets slow. Once the fan is pulling max cfm, it doesn’t need any more intake area. Not enough intake area & you lose too much cfm. Set the exhaust fan at 100% power for testing.
You can also run the test the other way & seal up all openings (not the exhaust), & slowly open up the tent door flap until you lose suction, if the fan at 100% power needs more intake area. Then measure the open area of the door & you know roughly around how much intake area you want.
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Good stuff there PhotoFinisH. What’s the reason behind a negative pressure? I read someone saying creates better air flow in tent.
Helps to keep the velocity up at the intake port(s), also helps to keep the smell in the tent.
Basic graph to give you an idea of what happens when you change the intake area. Too small & you have low CFM. Too big & you have low velocity at the intake port(s):
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I added a pressure demarcation line in orange. Once you have enough intake area for the exhaust fan to reach max cfm, the tent is at static pressure (right of orange line). Reduce intake area from there & you start moving to the left of the orange line into negative pressure & you start seeing the tent sucking in.
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