In the last couple weeks I have added a 30% Aluminet shade cloth over the top of my greenhouse, and also added a Wet Wall Cooling Pad system to the greenhouse (see link below). Building the Wet Wall system turned out to be a more difficult task then I originally thought it would be, but I got it done.. Between the two systems the greenhouse remains in the low 80s F (26C) during the hottest part of the day, when the outside temperature was 102F (37C). - Millet

//www.gothicarchgreenhouses.com/greenhouse_cooling.htm

Amazing. I presume the pads are internal to the greenhouse and that the evaporation increases the humidity? - probably useful in your climate.
From a total costing viewpoint, you are probably producing the most expensive oranges in the world!
We still need someone to invent a useable "heat-grabbing/6 months store/heat-releasing" box. Must be possible somehow....

Here in the UK we are suffering from the wettest, coldest summer ever - while still officially in a drought from low winter rains. I'm not currently allowed to use a hose pipe to water the plants - not exactly a problem as it rains every day. But I've never seen so many slugs and snails!

Mike/Citrange

Mike, you must know my wife, you both have the same vocabulary. Actually, is any hobby too expensive? - Millet (199-days from the 4th of JULY)

It has been a couple weeks since the greenhouse evaporative cooling system has been installed. During this time, two temperature sensors have been installed, and adjustments to the system have been made between the water flow vs the greenhouse exhaust fans. I preset the exhaust fans to maintain a greenhouse temperature of 82F (27C). The range of the outside daytime temperature for the last two weeks has been between a high of 105F (41C) to a low of 82F (27C). The cooling system has been able to maintained a constant greenhouse temperature between 82 - 84F. The system seems to work very well. The trees, and other tropicals like the temperature consistency plus the extra humidity. - Millet

Hello Millet,

Would these pads and this system work on a small 10x12 GH or is it too small. I'm getting my 1st GH but don't want to have to use a cooler or a/c in our summers here in Tubac, AZ.. We get low 100s to high 90's consistently for 3 months.. I'm concerned more about cooling than heating...

Robert, heating a greenhouse is much easier to accomplish, than is cooling a greenhouse. The reason greenhouses normally have very high roofs is to aid in maintaining a level temperature within the structure. Small greenhouse are very difficult to maintain a cooler temperature during the spring and suppler months If you look at the link I posted above you will see a picture of a self contained 5 sq. ft. wet wall cooling pad system. As far as I know this is the smallest system available, that works very well. - Millet 100

//www.gothicarchgreenhouses.com/greenhouse_cooling.htm

Throughout the summer I have been keeping track of how the Wet-Wall cooling system has been working. Five feet in from the Wet-Wall cooling pads the temperature remains around 77 to 79F (25C), in the center of the greenhouse (36-feet from the cooling pads), the temperature is an almost constant 80-F (27C), and at the exhaust fans (72-ft. from the cooling pads) the greenhouse temperature is normally 86F (30C). The Wet-Wall system has been working as good as I can possible expect. For those who are growing in a greenhouse environment, and are having a difficult time maintaing an optimum growing temperatue during the hottest time of the year, I highly recommend the system, it works amazingly well. - Millet

First congrats on building your own---it is pretty easy to do.

Two, I am surprised 84-85F isn't ideal growing temp.

Three, you may be able to lower the temps a few degrees further by adding a surfactant to the recirculating water (detergent). Just be aware that while detergent will inhibit some bacteria/fungus, it is a carbon source that can promote the growth of others. It promotes the more even spreading of water over the surface of your fibers for improved evap. It also can help lubricate the pump and lower the resistance of the water flow.

Four, evaporative (swamp) cooling works great until the dewpoint hits 55F, then that is all she wrote.

Fascist Nation, your correct, the use of evaporation cooling only works in the drier portion of the country . The eastern plains of Colorado is definitely a non-humid location. Counting all the rain and snow melt we average just 12 inches of moisture per year, and have very low humidly ratings. . Wet wall cooling probably would not work all that well in the deep south. Good growing temperatures for citrus is between 70 to 90-F. You are again correct that the optimal temperature is about 85-86-F, but the greenhouse has other varieties of plants that prefers lower temperatures, so I chose 80-F. Thanks for your input. Lastly, thanks again for the surfactant information I appreciate it. I was a chemistry major in college, and am familiar with many types of surfactants. I have never tried it, and wonder if it would cause a foaming situation. Have you had experience with cooling pads and surfactant? - Millet

In Naples Florida the company I worked for had an evaporative cooling system for some of the greenhouses. It rains in Naples nearly daily for most of the summer. It didn't work that well, but in the hottest time the day the humidity was lowest and it worked. It was also the only cost effective method of cooling the houses.

I'm growing citrus and many other fruits in a 1700 sq ft greenhouse in Alpine TX at 4500ft elevation. I also have a wet wall, 112 sq ft, and three 36 inch exhaust fans. I run all three fans only during the hottest weather. I can maintain inside temperature at or below outside temperature. Like Millet's setup that's about 80-85F at the wet wall and 95F at the exhaust fans. Summer outside runs low 90s highs with dew points 50-65F. The dew point is the most critical factor.

One fan with the wet wall on keeps things about as cool as three fans with no wet wall. So the wet wall is key.

I've placed the citrus on the hot end and fruits like sweet cherry on the cool end. The temperatures seem about ideal for all fruits.

I've got a writeup here with some pictures down in the post: http://forums2.gardenweb.com/forums/load/fruit/msg081351586372.html?11637

Fruitnut, very interesting post, with lots of quality information. Your greenhouse is similar to mine. My greenhouse is 32-ft. Wide X 72-ft. Long X 11-ft. High and at an elevation of 5,440-feet. I have 9 large in ground fruit trees, and a ton of container plants. All of the container plants are growing in RootMaker's Air Root Pruning containers. Most of my plants are various cultivars of citrus. You sure keep your greenhouse nice and clean. The main difference between a Texas greenhouse and a Colorado greenhouse is the cost of heating during the winter. On a normal winter season, my greenhouse heat bill runs about $4,000.00 per year. It is heated by propane. I don't have any idea what the cost of cooling is. Very nice having you as a member. Thanks for joining. - Millet

I heat to 50 - 55-F during the night. The day time temperature all depends on how sunny a particular day is. - Millet