Climate control in GH with fogging, swamp coolers and ventilation
 

I grow in a small GH in Bay Area, and have similar problems to others trying to create tropical environment in a Mediterranean climate (cold wet winters, hot dry summers) and find happy spots for hot, intermediate and cool growers in the same enclosure. I think this discussion will be most relevant to W coast orchid growers. Who are trying to achieve too much with too little.

I solved the problem with overly cold winters with a tight enclosure, grow lights and warm benches and cautious watering.

Summer overheating is improved with shade and the addition of massive wall vents that open automatically and a strong fan. Problem is Temps can still reach 100F and with increased ventilation humidity drops to low for many of the plants. So the benefit of fresh air can be offset by lost humidity.

I found automated misting created to much moisture with algae, black spot-rot etc in some areas and now only hand mist.

So now I am in process of adding a DIY large Swamp cooler, which I expect will keep down the temps, the vents will open less and the humidity will climb. (I am using a design similar to the 5g bucket cooler, but using a 20gal trash can, duct fan, and an autofill feature). Google DIY swamp cooler if you're interested.

Now the questions.
Should I add an ultrasonic fogger to really push up the air moisture content? Fog particles are 1-5 microns, much finer than mist. They tend to evaporate, not settle, there will be additional cooling but I suspect they have unique beneficial effects aside the cooling and humidity.

My thought was to put the fogger in the reservoir of the swamp cooler so the fog just gets blown in with the same set up. I could fairly easily put the fogger on a separate humidistat (set at 80%?100%?) with the swamp cooler on a thermostat set at 80F?

Anyone with thoughts or experience really appreciated.
Sorry it this is long and technical.

Plants should not be misted, the air should be. Running a fogger or misting nozzles under the benches is a very effective way to raise the RH without fear of causing rots.

That DIY swamp cooler is a humidifier, not a cooler. For a swamp cooler to be effective, it must take dry air from outside the greenhouse and eject cooled, humidified air into it. If you try to operate the unit inside it only, it will only work so long, then the RH will become high enough that it will slow further evaporation, defeating the purpose of the device.

Be careful about setting the RH too high - transpiration controls the flow of water through the plant, and that controls growth, so you don't want to stifle it with excessive humidity. Keeping it in the 50%-75% range is fine.

I have a 3 head ultrasonic mist maker (mister) on a float inside an ABS water tank (http://www.orchidboard.com/community...oom-setup.html). The tank is pressurized by a waterproof fan and the mist escapes through 2" pipe. Both the fan and mister are fed from a timer so that the mister is not overworked. Between the timer and mister is a humidistat set for ~60%RH. This works very well for me and the 12gal tank only needs filling every 1-2 weeks. The mister runs constantly on hot sunny days, and struggles to maintain 50%RH, but otherwise it runs about 1/2 the time and keeps the sunroom at +60%RH.
For cooling, I just use an old window A/C unit, set to come on close to 90F. A tower fan circulates the air throughout. Sure the 2 units "fight" each other when it comes to humidity, but I like knowing my cooling unit will effectively drop the temp, regardless of room RH.

I use a swamp cooler with a small greenhouse in SoCal, and works well, by and large. The GH is not fully closed, so it gets the cooling action going. I also have a 5 disc ultrasonic fogger in the 4x9' GH, automatically controlled to come on at RH<70%. I then have misters that go off for 1 minute every 15 minutes mostly towards the sphagnum of very sensitive plants (malaxids), if RH is < 50%; some heads also do under bench misting.

Watering is by hand. Below ~75F every other day, above 80 certainly every day. Most of my plants are mounted.

Everything is run on RO water.

I have an 8'x6' GH, I have a large swamp cooler that is run at medium, its on a thermostat set to 90, I put two cheep dryer vents at top side of greenhouse on both ends, they open when cooler come on and vent out hot air. I also have a 14" fan mounted to center ceiling, that blows upwards and that start to run at 70 degrees, that help with circulation. I do have misters under tables that come on every 2 hours for 3 minutes. The temps in GH on a 100 degree day will maintain at around 90, RH 50% or better, I have a nepenthes that will stop producing pitchers if humidity stays low with that plant I can visually tell if RH is low.
My plants really seem to like GH, have good succes with several from warm to cool, coil if near cooler exhaust. My biggest problem was potted plants I have lots of mounted plants above tables and they need daily watering which would keep medium in pots to wet, so all my potted plants now grow in chunk gravel and styrofoam, moister loving orchids(Paph. Phals. Etc.) have a pea gravel and chunky bark mix and pumice, they all seem to put out more roots with this medium and healthy roots mean healthy plants and flowers

My summer conditions are hot and dry. My greenhouse is 8x12.
I have a wall ventilation fan and a swamp cooler on thermostats and a mister on a timer.

The thermostats are set so the fan comes on first and if it gets too hot then the cooler kicks in.
I use the misters in the afternoon when the dry heat is greatest but not for too long.
Ray is right about the cooler needing to be outside. I keep the door of the GH open all the time in summer.

It doesn't need to be a jungle in there. I've seen a noticeable improvement in my plants with just the humidity the cooler provides.

Maureen

thanks
 

Thanks, especially from all the California responders. I have some aerial, most of the potted stuff is in SH-LECA, or very dry bark-Lava also to avoid them getting overwatered. I found the Intermediate and cool growers do need finer more retentive mix, and have been slow to adopt to SH culture for me (sorry Ray).
I decided to run the Swamp cooler (placed on outside) on a thermostat the cool air will pump near the large circulation fan. I will make a small fogger (3 head) in a 5G bucket with small fan and set that on a Humidistat. The ventilation windows already work well with the automatic openers so I should be good.

Everyone's situation is a bit different.
It's fun to experiment, let us know how it turns out.

Maureen

No apologies need to be directed to me; "S/H" does not fully define orchid culture, and there are lots of plants I can't grow that way either, while others have no problem at all.

I think the primary flaw in most folks' "conversion" to S/H culture - assuming the rest of the conditions fit well for the plant - is poor timing of the transplant.

As to the swamp cooler, I think your outside-in approach is a good one.

OK its in DIY Swamp cooler works great, pumping in really cool damp air and uses only 82W (70W fan 12W pump).
3 head fogger is neat but does not produce enough fog to raise humidity above 40% in my 8x12 GH with vents open on very hot day. I will need to buy the new 12 head fogger which puts out 3L/H and add an autofill valve.

Anyone looking into fogging I recommend going bigger, as long as it is on a day-night or timer supplemented humidistat to turn on / off and avoid excess.

I am going to add a 3pole toggle to one of my heater thermostats (I have 2) and to switch back and force from heating-cooling with the seasons.

OK got the 12 head fogger now, set on humidistat at 80%. Swamp cooler is on thermostat set at 75F. I wired my old misting system solenoid to a thermostat and used a relay switch to activate the fan so I have a back up misting fan set at 90F if the other systems are not adequate during a heat wave. The interior environment is much better I saw 82F and 80%RH at mid day on a warm summer day!

Question, is it ok to run the fogger-humidifier 24hr/ day?

12 head fogger is in 120cfm fan is strong enough to blow the fog up 6ft or so which is important as the fog is heavy and settles to floor quickly. With Swamp cooler bringing in fresh and cool air, I decided to close and inactivate most of the auto cooling vents. I am seeing 80F and 60-80% RH so now GH is really an orchid house!

Question, can fogger run 24-7 if on humidistat set to 80%?

All I can tell you is that I did that, and the plants loved it.