I flower my ladies at 50% humidity and do not have any powdery mildew or bud rot which I attribute to my Oscillating fans and exhaust/inlet fans. I have the ability to run a lower RH but I choose not to for several reasons. The first is a heat concern, especially during the summer months. My dehumidfier exhausts heat into the room. It would take a major modification to get the exhaust out and not to mention the added filter for odor. This is a constraint more than a choice, I know, but I can run cool enough at 40% if I wish.
The second reason I don't go below 50% Rh is that plants transpire much more at lower humidity levels. For hydro that means bigger swings in ppm with smaller resevoirs and having to add back more water more frequently. Even when I am running at 40 gallons in the res. I notice larger swings in ppm with lower Rh.
I would rather the plant use the water in it's cells and cell walls than stress it constantly by making it work harder to cool itself. There are other ways to stress a plant for more trich production that don't stunt growth as well. One that is beneficial is simply "light intensity". Getting your lights closer to the tops increases the trich production in response to the increased intensity. Just as long as the light is properly vented, heat stress which IS detrimental to growth is avoided. I like to keep my lights about 8 to 10 inches away for optimum coverage and intensity. nearing the end of the flowering phase, the last couple of weeks, I lower the lights every other day to 4 inches above the tops.
I say experiment. Find what works in the environment you have and watch the ladies responses. That is the best way to fine tune your garden environment. If you can add a dehumidifier without negative consequences, I would do it. I am going to be adding A/C to my room which may negate the need for my dehumidifier and eliminate the heat it produced. However, I suspect I will still maintain the Rh at or near the 50% range even if I can lower it without negative effects on the environment.
I appologize for the lengthy reply, I am waiting to see if I am working today or not and your thread had the misfortune of catching me at such a time.
