Trying to avoid Powdery Mildew while maintaining proper VPD levels

Beginner here trying to stay ahead of the curve. Im trying to stay in a certain VPD range that range definitely is keeping my humidity pretty high in early vegetation. Should I tone down my humidity to avoid Powdery mildew?

Healthy plants in veg rarely show mildew. Keep airflow and temps up and you won’t have any problem.

I normally run near 60% RH in flower due to my situation but the climate overall is so dry here that there are few mold spores present. It just kinda depends on your setup and climate.


My challenge is im in a room with no insulation so at night the temps get low. Should I be turning off my oscillating fans at that point with lights off to keep humidity down?

Fans should be running nonstop. You may have to introduce a dehumidifier into your grow space and run during lights off as that is when humidity tends to peak.

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Yes, I do

Fan setting will exchange tent air once per minute, min
One Oscillating tower fan and one small clip-fan.
AC-I Cloudline Controllers for T6’s (should have gone T8’s, more power)

Controller has software calibration for leaf temperature (manual input required, from IR-gun) and calculating VPD with air temp (attached probe sensor).
Good Groing to you.


You would probably open tent to water all over. Oscillating fans must run. Plants need strenght training as well as transpiration cooling.
More air exchange, increase temps, or watering less will reduce RH.
Heat retention is my problem also. i posted forum thread “RE-VEGing a continous grow”.
10-2 twice daily will become 11/1 twice dailyand I will offset my two tents so both are on at night, during coldest, like summer, but cold in lung room.

Good luck