Growing space air movement

My exhaust fans are running 24/7 no matter what stage of life the plant is in.

If you supplement CO2 in your tent, the exhaust can be used as a reaction to RH or temperature, but in a normal context of ambient co2, you should hve it running 24/7. Just enough to keep co2/o2 levels equal to what is outside the tent. O2 builds up and CO2 reduces inside due to plant transpiration. CO2 is the plant's limiting factor. It doesn't have to be running 100% by any means. I run my intake/exhaust duct fans abotu 25-50%, depending on context. Can probably reduce at night if you have a controller capable of that. The more efficient duct fan otions aren't more than 20-40watts for a 4"-6" fan. My 8" is 80w, but again only runs at 50% max. So, overkill isn't a bad thing and doesn't cost much electricity. Better to err on that side, anyway.

The amount your exhaust comes on should be set by the rh footprint. When your plant grows more water is moved, as it gets bigher and starts to move more moisture the more exhaust needs to come on to deal with it. Less of a veg thing and more of a size thing. Your job is to understand SPAC (soil plant air continuum) transpirstion by day (water from soil) respiration by night (water from air not soil) Optimal condition for transpiration are different than than from respiration at night as transpiration is endothermic respiration does not have latent heat for process of cooling. When you calculate vpd during day use a 1F-5F difference based on how much a plant transpires because when you calculate vpd it's more accurate to use leaf surface temp and not ambient, leaf surface will always be 1F-5F cooler than ambient canopy due to endothermic cooling. Evaporation Transpiration Evapotranspiration Respiration You can run higher rh ofc in veg just be aware higher rh lowers transpiration, so long as you are confident water is cycling its OK but the second transpiration stops or slows, the only way water is leaving the pots is evaporation, if rh is high nothing will evaporate from pots water will stagnate. Just make sure it's not 60rh daytime peaking to 80rh at night just destroying respiration. With no heat at night we need a decent airflow, fresh supply of o2 if limited, lower humidity to assist with dealing with rigors of respiration.

The idea is basically the Archimedean property, you can fill a bathtub with a spoon. In other words, inflows win when you let time extend to infinity. So, you modulate the tent conditions by controlling inflows/inputs. This totally depends on your set up. What type of lights are you running, are they passive or active cooled, etc. Is your environment outside of tent sealed, how is ambient CO2 levels, RH, temp, etc. My exhaust is usually on the lowest setting during veg unless I let them get really bushy or the weather outside is impacting the conditions indoors. For flower I'll crank it up. I don't like the noise pollution of exhaust fans, so I really only turn it to max if the girls are so big that keeping RH below 60 requires it. The whole high CFM thing is likely unneeded unless you are pumping DLI out or have low CO2 in your home (unlikely unless a new build). A CO2 meter is pretty cheap and should give you confirmation one way or the other if you need to be turning over the air in your tent more quickly.

I've recently started running my exhaust on a timer in one of my tents to help raise the temps in there a little bit. It's another option in the toolbox for environmental control. As far as what's the minimal amount of air you should move through your tent, that's gonna vary based on the size of the space and the size of the plants. You'll see humidity spikes more the bigger they get. You'll also see even bigger humidity spikes after lights out, so keep that in mind too.

I’d say at minimum when plants are smaller to run the exhaust fan for 10 to 15min every hour or so. Also if you put your exhaust fan on the lowest setting it will normally will help rise humidity. Also if you have a super small grow tent you might not want to use a full size exaust fan they can be to powerful for a small tent. Amazon has cheep inline duct fans that you can use as an exhaust fan there less than 20$ and they move maybe 1/4 the speed of a full size grow tent exhaust fan… also if you just get a cheep humidifier and set it up outside your grow tent after a day or so with the humidifier on it should help rise humidity in the entire lung room

Hi there, in my opinion you are right. I only have passive air ventilation as long as possible. You will get wild theories about the air exchange rate. I am not saying it's all rubbish, but I won't ever get the idea of changing the complete volume of a tent in seconds, most likely due to "keeping the CO2 feed/rate" high 😂😂 I would spare the noise and energy. I use my filter system for heat and odor control, nothing else. 😅 Regarding filter and exhaust, humidity is something else in my opinion. I don't want to dry the air in my filter and exhaust. Running it with RH like 70-80% is not an option for me. Moreover, with your small box I am not sure you will get a stable environment if you change the air too much, except your surrounding is in good (better than mine) control. In sum, I don't have a rate or something. - If it smells turn it on, just enough to force it through filter (for my 80x80x160 this is just the standby - mode!!!!)

Also ich steuere meine Ventilatoren mit eine smart Steckdose und dann über eine Handy app. Und diese laufen 1 stunde und pausieren dan 1 stunde und das durchgehend 24 stunden immer im Wechsel, so wie in der vege- als auch Blütenphase. Bei Bedarf halt umprogramieren