My thought is that with venting, you would be wasting a lot of supplemental C02 and cooling with intake/exhaust. After you get the minisplit, you are half way there to having a fully sealed climate controled room/environment , why stop there? A good dehumidifier is pretty much all you will have left after mini split and co2 injection. I just bought two twenty lb co2 tanks to swap with each other for the sealed room I’m building and i plan on filling the room up with CO2 an hour before my lights come on, and on a timer releasing CO2 the first 15 min of every hour while lights are on. This is without any intake exhaust setup in a 8x12 room and even so my tanks will likely last 6-12 days each releasing 1000-1500ppm I’m told, maybe a tad longer . I might even opt to get a third twenty lb tank just to have on hand. The 50lbs where just too heavy for me to lug around. Sorry to keep editing I’m waiting on my first cup of coffee lol. Still waking up.