E-mail – High Humidity Cures

Doc, Thanks for the quick response. I'm also having a problem with humidity.  Any suggestions on how to bring it down. I have a fan to circulate the air and an exhaust fan taking air out but my humidity is still to high. Thanks for your help.
No problem I am always glad to help. High humidity usually is not a problem for plant growth but can lead to mold. I say this since high humidity won't slow down plant  growth unless it is very high, say over 80% humidity. Plants need to give off water as part of photosynthesis, so if the humidity is too high it might lead to slowed photosynthesis which can slow growth and lower yields. If you don't have mold, and never did it might not be a big problem for you. I also mentioned that many pests (aphids, soil gnats, root aphids and others) like high humidity so lowering the humidity might help people that have pest problems. High humidity is also something that really limits the life of carbon filters
The easiest thing if you can spare the space and electricity is a dehumidifier. I find that when I start using my HPS, it lowers the humidity in my grow area. Many growers only have small spaces  to grow in so maybe you don’t have room for a dehumidifier.
Do you have open water, as in a hydroponics set up or water in trays after you water the plants? If so you could try to cover the hydroponics medium to prevent some evaporation (not easy with some set ups) or drain the water trays a few minutes after you water so there is not standing water. If you don't have water in the room, the next thing to think about is that the plants put out water into the room as part of photosynthesis, so the more plants you have and the more you water them, the higher the humidity. So, you could try to water the plants a bit less, but not so much they wilt, which will stress out the plants and slow growth. Moreover, you could try running the exhaust fan longer, maybe even when the lights are out, or upgrade to a bigger fan which will move more air/water vapor out of the room. You should try to exhaust the air to the outside of the house, otherwise you are just moving the humidity around your house and not really getting rid of it. Something else to try is to put corn starch, baking soda, talcum powder or silica gel in the room, these tend to absorb moisture. You will need to replace them every month or less if you have very high humidity. I hope this helps.
Good Growing
Dr. E.R. Myers