New grow space not new to growing. Soon I will be going up from 8,000 watts (4 lights in a 12x13, 4 lights in a 13x14 room) to 16-24,000 watts (16-24 lights in a 16x23 room). Putting the down payment on the property and building the room has me pretty tapped and I have yet to get any equipment so I am afforded the extra planning time. I have 2 options, sort of..I can go with air cooled hoods loosing 5-15% lumens and only being able to put 16 hoods in plus the extra hassle of cleaning all of them in between grow cycles..or I can get the simple batwing open reflectors and just cool the room. There in lies my question, I need to cool the room. I am thinking of building heat exchange ducts on either side where a 8"x24" square duct runs the length of the room. Inside the duct there is 4" flex duct coiled so as to bring the cool air from underground outside in (while keeping it clean) and run the hot air in the room over it and back into the room. Simple cheap and effective. What kind of AC am I looking at? How many BTUs would be needed? Any thoughts on the matter?