I'm having trouble dealing with humidity control in my 9x14 gh. Basics are: 10mm twin wall on wood frame with 3' cement block knee wall and mortared common brick floor (with drain) I'm in Zone 9 (Sunset 15 or so - near the coast in CA) Only need to use 1500 w milkhouse heater to maintain mid 50's during clodest nights and use 50% shade cloth during late Spring, Summer and early Fall. Have two 16" shutters installed in lower front face (each side of the door) and one 16" vent fan mounted center just below peak on back (west) wall. Pics are here if you want a visual.

http://s40.photobucket.com/albums/e247/clavero/?

Last summer I installed a misting system (not a fogging system) with nozzles mounted on ceiling along each side. Last Summer I used it only on a timer (not on a humistat) and ran it once an hour during daylight hours; while our summers can be hot and dry during the day and cool and moist at night, that install seemed OK, even though I knew I really needed a humistat to do it right.

During the winter, even taking care not to water late in the afternoon, the humidity would usually rise to 80%-90%+ at night, with the gh holding 52-53 degrees F. I knew this wasn't good and sorta kinda tried to deal with it by leaving the door open on anything that looked like a mild day (even when cool) but did not think that running the exhaust fan at night when the temp was 35F was a good idea to reduce the humidity.

Last weekend I installed a humidstat on the misting system and set the control for 50%. The misting system went on and off throughout the day in response to this setting while the exhaust fan is working on keeping the gh cool during the day when the outside temp was 80 degrees.

By two hours before sunset, when the gh is basically in dappled shade, the humidity was in the 50's but the mesh bench tops, pots and plants were all visibly damp. I left the gh door open till dark (still 60 outside) but by 11:30pm the gh temp was 55 with 89% humidity.

So.....first I'm clear that I don't like the misting system...the nozzles drip for a while once the pressure stops, leaving small puddles and the plants beneath the nozzles can get pretty wet.

Two questions arise for me: (1) Anyone care to weigh in on their experience with the Aqua Fog 400 vs the Trion 707 humidifier? I like the Aqua Fog idea but the video seems to show the unit blowing enough mist for the Golden Gate Bridge during the summer with a 35kt breeze, while I'm not sure I like the sump with float valve idea on the Trion.

(2) What I'm I missing here about the humidity control at night?! I can close the gh up at sunset with a temp of 65 and 55% humidity and in the morning find it sitting at 53 degrees with 94% humidity. This with no standing water on the floor, no pond, no mister on?

I can see that if I set up another smaller exhaust fan on a dehumidistat that I could get changes of air during the night to keep the humidity down, but then many nights I'd just be blowing out the air that the heater just warmed.

As always, any advice or suggestions gratefully received.

Steve