Greenhouse: Greenhouse humidity, 0 by nautical99

nautical99 wrote:
I have been very concerned about how high the humidity runs in my GH, so this trhead and others have been a big help.

I am also in Zone 7b, and it is very humid here most of the time. I have been tweaking the thermostat on my exhaust fan, and my heater trying to get the humidity down.

As has already been noted, my humidity is always the highest in the early am. Now that the days are short and it is cooler outside, my exhaust fan does not come on as often. I was letting it get up to 85-90F for awhile, but it was just staing too humid, usually about 90% most of the time. I have lowered the thermostat to 80F, and now when the fan comes on I can see the dip in humidity.

Of course I can't have the fan on at night as it is too cool now, and also many times as soon as the sun goes down and the temps drop, the humidity outside rapidly climbs, and before the night is over it will be more humid oustide than it is inside the GH.

I had to go back to IL for a bit, so just before I left I turned the thermostat up in the heater. By raising the temp I have noticed the humidity has dropped to a tolerable level.

I run three circulation fans inside the GH. One fairly high volume fan down oneside, another smaller fan on the other that is also pointed toward the ceiling to move trapped hot air from the peak, and I also run a small circulating fan on the floor, under one of the benches.

The sensor I use to monitor temp and humidity is also under the bench on the back wall. I have another temp and humidity sensor that sits on the top shelf. I noticed the morning after I turned the heater thermostat up that there was about a 25% difference in the readings of the lower sensor and the upper.

When I get back home I plan on moving the sensor up above the lower bench and below the top shelf and see how much the readings change.

As I am so new to ALL of this, not just my first GH but my first at trying to grow things in general this thread has been most useful. Thanks to all that have contributed.

The graph I am enclosing is a plot of the last four days of the conditions in the GH. I have superimposed two red line that show where the fans came on, and how the humidity dropped at the same time.

I think I will have to continue tweaking as I don't think I need to run the GH at 70* at night.

Would it be feasable for a hobbiest to just purchase a de-humidifier and run that? I am not sure it would be cheaper to run that then it would be to just keep the temp a little higher.

Sorry this is so long, thanks for all the help and advice here.

Nautical