We are now in winter and temps are falling. Low 5.5c to a high of 12 c. Current humidity 83% 9.14am
83% sounds bad but it's cold air so thats super dry. Blow that in to cool your flowering room and it will drop the RH% for you. For example 5c at 85% has 4.59 grams of water per kilogram of air. Warm that air up to 80F and it's at 20% RH. The "relative" in relative humidity is a big deal.
What about summers? What do the numbers run then? Don't wanna be stuck having to vent more since the air is warmer outside and end up with the humidity too high.
In the current situation with the cold dry air, it won't take nearly as much air exchange to cool the room, in fact a system sized for summer would probably only run a few minutes to drop the room temperature and then shut down.
Any type of vented grow is a balancing act because of the ambient temp / RH% variables. Sometimes you can't get good numbers because the outside air is too hot or too humid. Running at night is obviously helpful for the heat but could actually make the RH% number worse.
If I was setting up such an endeavor, and the ambient absolute humidity # is generally low I would want two means of controlling the environment. The ability to run sealed/co2/dehumidification and AC as well as the ability to run vented when the ambient allows it to save money and be a backup for the AC. This is how I am setup because the air is so dry here in Colorado. If I had humid outside air in the warm times then I wouldn't even bother with the venting option and just go sealed.
Right now I have my flowering rooms running with AC and CO2, dehu. But I sometimes just turn off the dehu if the air is dry outside and temps are workable, then if the RH% hits 50 the room vents down to 40% and then the CO2 generator kicks back on... So I am using the intake blower as a dehumidifier. Lest nite, this AM the ambient RH% was too high so I disabled the venting and turned the dehumidifier on until the #'s went down this afternoon.
So really unless you wanna be dicking around with the setup all the time, you want sealed, AC, Dehu and CO2.
Note, I run intake fans and the exhaust is passive as I don't need negative pressure for odor control (I run scrubbers).
The ONLY reason that I can really run with venting is the very low ambient absolute humidity numbers that I have 97% of the time AND I have AC/dehu/CO2 for times that the humidity is too high.
This neat chart lets you see the RH% changes from temp.
So it just rained outside and we take outside air thats at say 15c and 95% RH (10.11 g/kg absolute) and blow it into your room thats sitting at say 27c and that air is at 45% ish. Does that make sense? So now we have 18c / 95% air going into the room would be more like 55% (not good for flower cooling). Lots of fuckery if you don't go sealed.
I hope all that helps. It's not a simple thing and with an op your size you better have really low ambient absolute humidity numbers all the time. Would suck to get 7 weeks into flower, have big ass buds going, rainy season hits and the ventilation you rely on for cooling is pumping in so much added moisture that you get bud rot. Know that a dehumidifier or humidifier can't keep up with a ventilation system designed to cool 60kW, may as well set it outside and run it lol.