misting systems/cooling gh
 

I'm going into my first summer with my new 14x28' greenhouse. I live in hot, humid coastal South Carolina. Have got 70% Aluminet raised a few inches above the roof. I'm researching installing a misting system for cooling and to raise humidity.

Anyone have any info on the effectiveness of over the bench vs. under the bench misting for keeping temp down? Pros and cons either way? I'd like to keep my foliage pretty & worry about misting above causing deposits, but foremost I need maximum cooling.

How about use of a humidistat vs. setting timers to switch system off and on? I'm inclined to think the humidistat would be worth having, but are they a problem w/maintainence?

I know either way to have the system shut off a couple of hours before sundown.

What type of misters? - 2 gal/hr ??

Thanks in advance for any experiences/advice.

Hi Carolina Girl,
I am surprised there has been little or no comment on your question. First off, I'm jealous of the size of your greenhouse!!! But here goes. I don't use misting as I live at3400 ft in the western N. Carolina mountains. But in the past I have been exposed to lots of methods. If you put your misters high in the peak of your GH you can get cooling easily by evaporation and not too much on the foliage and in the crowns of the plants(crown rot being a problem with too much moisture) I would use 1 gal/hr to start even tho you might want more later. Under the benches will provide humidity and cooling but you will need to circulate the air to get good cooling effect. Under the bench you can easily use 2gal/hr. Another thing to consider which I used in the past in warmer locations is the evaporative cooling pads at one end of the GH with the air pulled thru by strong fans at the other end of the GH. This provides good cooling at plant level and also good humidity. It works like a swamp cooler in the desert, but is really effective, especially if the outside air is low in humidity. Various GH companies have evap. systems that can, with some work, be installed in most any GH. If you need more info let me know. Will be glad to help. I often go to Edisto Island, as it is shorter to get there than to the Outer Banks of NC.
Andy

Hi, Andy,

I spent the day on Edisto yesterday at Edisto Island Open Land Trust's Nature Day. No better way to spend a day!

I've been trying to find info on the actual mister/sprinkler heads without much luck. They seem to usually give the gph, but nothing about the type. Do you know if there are different types for misting/fogging vs. irrigation. That is, are some designed to put out a finer spray, or do you just use the lower gph types for misting?

Thanks!

Hi Carolina Girl,
I was in Edisto about three weeks ago. A friend of mine has a home on the sound side and we go there.
If you will go to the net to www.littlegreenhouse.com you will find lots of information on misting systems and the various types of misting heads and cooling systems. On the left side of their page click on Misting Systems. And to answer your question about misting vs. irrigation there is considerable difference in the heads and their output. There are lots of sources of this type of equipment so if you want more info let me know.

Andy,

That link is a great one. I wish I'd found that site a long time ago, since while poking around I found the solution to a problem I had last winter. After I sealed up the gh for cold weather, every time the exhaust fan came on the intake shutters could not open against the vacuum caused by the fan draw. I was having to crack the manual vent each morning to allow the venting system to work when it came on, which is needed on all sunny days here, even in January. We looked for a delay circuit to delay the fan, but the only type that would work was very expensive. But the two stage thermostat offered here should do the trick nicely.

Good info on the misting systems, too, BTW!

I lived in Georgetown for a few years, and did not have any misting at all. Instead, I relied on ventilation.

On the south-facing end of the GH were two 18", motorized, louvered shutters controlled by thermostat to open at 65°. In the north end was a 36" louvered shutter protecting a belt-driven fan. It thermostatically turned on at 85°.

All were as high in the end walls as I could get them, and were screened to prevent bug intrusion.

I went that route instead of misting, as the ambient humidity level simply slowed evaporation too much.

Hi, Ray. I've got ventilation similar to what you describe, good fan & 2 vents up near the top. But to the south and west is an open pasture, so I get absolutely no shade after 10:30 am. My gh is already getting up into the 90s with days around 85 degrees. In July and August, I expect it will be topping 105 most days. I have some 30% shade I can add to the present 70% Aluminet, but I don't expect it will help much.

Were you able to keep most of your plants inside in the summer? Maybe I should not hope to keep my plants in the gh during the summer at all. But I hate keeping them in the yard. Always problems with wind and critters dumping plants over. I would not be too upset to have to move them out for July and Aug, but I am hoping not from May 1 to Oct 15. And either way, it is getting to be a problem to house them outside without building a shade house too! My plants have expanded beyond the capacity of the racks I was using.

Maybe I should just stop buying orchids??? Anybody know a cure? Orchids Anonymous??

I live in hot and humid Houston. My little semi-homemade greenhouse has shade paint on roof and addition of 50% aluminet on the south facing roof and wall. I found very quickly that I needed additional cooling. I bought a misting set from Sam's warehouse and my husband bought a timer from Home Depot that allows for different choices for misting. I was also worried about how to mist. I am now misting from above and below the bench. I only mist for two minutes at a time with six minutes between each misting during the chosen time periods. I see that this method can drop the temps very rapidly and keep it around 85 to 94 degrees versus more than 100. The last misting is a 4:30 which allows the plants to dry out before night.

Sandy,

Did you get the Misty Mate system made for patios, by any chance? I've been looking at them & see them offered at Sam's.

Do you know the gph rating of the mister nozzles you have?

Some folks locally here have told me that they use 4 gph nozzles and only run them a few min every 2 hours or so. I'm thinking that running low output (1-2gph) fogging nozzles for short intervals frequently, as you are doing, makes a lot more sense for cooling the gh.

Yes it is the mistymate made for patios. I do not know what the gps is but I can tell you that it does not use that much water in the day the way I set it up. At first we only did under the bench on one side of my little greenhouse but my friends that mist from above convinced me to put some in the roof peak too. So far everything seems to dry out by dark. My timer can be set so that I start the first cycle at 11:00 to 11:30, with two minutes misting, then six minutes resting, then repeat until the thirty minutes are up. Then it does nothing until the next cycle. The thirty minute cycles are one every hour from 11 till 4. This seems to work for me but can be changed to suit oneself.