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Hey guys! I’m 5 weeks from seed into my latest grow and so far so good, I can’t thank you guys enough for all the content. Best $10 a month I’ve ever spent! Using build a soil coots mix and following their complete growing system with the addition of recharge, of course! Growing in 10 gallon radicle bags under a HLG 550 v1. Happiest ladies I’ve ever grown!

As my grow is progressing I’ve decided I need to be able to drop night time temps lower than my room is going on it’s own. I built a new 8x8x8 grow room in my basement and decided with a little advice from the DGC to run it sealed. I’m using a Saturn 6 environmental controller to handle heat, humidity and co2. I’m running about 82-84° in the daytime and without A/C my night time temps drop to about 72-74°. When my controller lowers humidity after lights out to maintain proper VPD I get a short raise in temps because the dehumidifier is putting out warmer air.

I had it in mind that I could just run a 4″ can fan with a dust shroom from the adjacent room that stays about 65° year round to bring in some cold air. I bought the stuff to do it but then I realized I can’t add more air to my sealed room without creating positive air pressure and forcing air/odor out any cracks I may have.

The environmental controller has a cooling outlet as well that I can set to come on during lights off and run until a set temp is reached. First option would be active air exchange. I would use a 4IN can fan and dust shroom pulling cooler air in from the adjacent room or outside, then use a 4IN can fan with a carbon filter exhausting hot air out of the room or house. I wouldn’t expect the fans to have to run long or often to lower the temp and since my plants aren’t using the co2 during lights out anyway it seems like a decent option. Another option would be of course passive air exchange using the 4IN can fan on the carbon filter , and a larger air intake with a larger dust shroom, maybe 8-12IN.

Otherwise my option is of course to buy a portable dual hose AC and keep the room completely sealed.

Are there any down sides I’m missing to exchanging the air during lights out? I realize it would cost me a little more c02 when the lights come back on to raise it from ambient to what I run my room at, what else? Would it be difficult to keep the duct work sealed when the fans are not active? I’ve seen one way baffles for the 4IN duct, do they seal well when not in use? The last thing I want to do is let all my warm air out in the daytime or create a path for critters or mold etc to get it because I have duct not sealing up when the fans are off.

I’m not against buying the AC and I feel like it’s probably the obvious choice, just brain storming of other more cost efficient options during the cold months.

Thanks in advance guys!