How fancy do you want to get?
A system that is closed means less waste, but you need more creativity in cooling.

Here's the setup that I have run successfully:

My space was a cellar that stays cool on hot days.
The total footprint is about 6 x 20 feet with a 6.5 foot ceiling.
The end of this room is blocked off by a wall that has 2- 6" holes drilled in it with a hole saw. WARNING! 6" hole saws KICK like a damn mule!
There is also a 1 x 2" rectangle cut out that is large enough to let a light cordset pass through.
The lower hole is the intake, and is set DIRECTLY in front of the cold air OUT part of a portable a/c (9,000 btu, about $300 at home depot).
The a/c is vented out the cellar door, that has a 4" hole cut in it and masked by a louvred dryer vent cover.
The rest of the space is just the 'lung room'. There's an area where I keep my two ballasts up on milk crates off the floor, my co2 tank and regulator, an indoor-outdoor thermometer (the probe is stuck through the lamp cord hole, along with the tube from the CO2 tank, and they both hang down into the middle of the room), and a ~260 cfm muffin fan that is pulling air OUT of the 6x6x6 2k bloom cube and into the lung room for cooling.
The walls of the lung room are masonry and there are fans blowing within the room. Air cools off quickly once it leaves the bloom room.
CO2 enrichment is functionally of the entire space, since the 2-room system is actually for climate control in a closed but divided 'grow suite'. Since I'm enriching the rest of the suite, I keep my moms in there too, just obviously out in the lung room.
Hot air is moved out of the bloom box via a 6" open-ended air-cooled hood. It then flows over light#1, through a ~4" straight length of duct, through light#2, through a 2' section of 6" duct that passes STRAIGHT through the wall, then through the muffin fan, then through an odorsok and into the lung room for cooling.

I run both active and passive cooling, using a/c for the 'active' component and thermal mass of the brickwork for the 'passive'.

Controllers allow for both; you will want to have a high temp sensor/controller that allows for rapid exhausting of your room if temperatures over ~85'F are detected at the probe. I don't have my system configured this way, as I am now assured that the cooling I run is sufficient and temps have never required emergency exhausting.

I hpoe that helps.