Keeping Greenhouse Cool

[auntymo]

as i understand it the problem with air conditioners in a g/h is that they cool most effectively AFTER they have removed most of the humidity from the air.

depending on the size of the g/h though this may or may not make a big difference.

--mo--

[WolfinKW]

well don't think that would be the case with this one since the only thing it has is a heat exhaust that goes into a window. It has a drip pan inside that needs to be emptied however if you just routed that into a pan for evaporation or just let it run onto the floor of the GH you shouldn't have an issue with humidity. But that's just my reasoning of it. Because there isn't an "outside" portion of it like there is with window air conditioners.

[LJA]

Mo is correct about using AC. Effective cooling only begins after the units pull moisture out of the air first. If you counteract that by adding moisture back in, you're working at cross-purposes, and neither the cooling unit nor the fogging unit achieve their potentials.

A few summers ago when outside temps were ranging in the 115 - 120 range for weeks on end, we had an AC unit installed in the GH here. It helped very little, and only if run concurrently with the pads and fans (it couldn't keep up if the shutters and exhaust fans were off, heat just continued to build up regardless) but with exhaust fans on and the air conditioner outputs aimed down, it did manage to keep the plants at bench level at about 100.

Foggers are extremely effective, and many people run them *under* their benches to avoid condensation in plant crowns. I think the only reason more people don't use them is the cost, especially when compared with evap solutions like pads and fans. Of course, in areas of extreme humidity, evaporative cooling accomplishes little....

[Manchua]

>But all this reconfirms why I am in no hurry to get a greenhouse. This is way too complicated.
>Too much math - all these microns and parts per billion or whatever....

Hehe. Yeah. I know. But they are orchids. They deserve pampering.

>My concern is that if I use a auto drip system to create a large particle fog or
>small particle mist, then depending on the heat, humidity and air flow, I'm liable
>to end up with that free moisture on leaves (crown and/or new growth).

Why not keep the mist from settling on the plants by keeping something just above them. The mist is meant for cooling anyway, not for hydrating the plant. So you can build a shelf immediately above the plants to keep the mist off of them.

Of course, there is the inevitable problem of getting together a system that is dependent on electricity. If your power goes out, your precious orchids will become onion rings within a few minutes, particularly here in Central TX on a midsummer day. So even if you're in town, but across town, it might be too late for you if the power goes out. There has to be some kind of backup if the coolers go out. Shade will only keep the temp equal to the ambient outside air at minimum. So if the temp outside is 100F, it's going to be at least 100F inside the G/H, and very likely higher.

Even if I could guaratee that the power wouldn't go out, foggers have their disadvantages too because of the minerals that are left behind. Foggers that have water reservoirs can be used with rainwater, which eliminates this problem. However, you'd have to have a lot of rainwater. Even though foggers (not misters) use very little water, it adds up to several gallons per day. Now imagine going through a TX summer where you need to cool the air in the G/H from around 10 a.m. to 8 p.m. for months on end. We have barrels totaling about 350-400 gallons of rainwater, but this would go quick at 1 gallon per hour.

Here's a good article on G/H cooling: http://www.gpnmag.com/gpn/index.cfm/...articleID/4032

[WolfinKW]

The only thing I'm wondering is why buy one when all you really need that you can't do it yourself would be the specific pads aspen shavings in a form of somekind is what the one site I saw recomended. The rest just sounded like a blower forcing hot dry air through them and a pump to pump water to the shavings. You could make it as big or little as you want and if you think about it... it may be possible to use the same motor that drives the fan to move the water in some way.

Wolf

[LJA]

We made our swamp cooler ourselves out of roof gutter and a cattle watering tank. The pads fit perfectly in the gutter ledge, and it was just a matter of drilling holes in the PVC pipe above them to make a spray bar. Gutter above them and below keep the water contained. We had to buy the electric louvers of course, but the whole system cost less than 1/4 of what a turnkey papckage would have run.

[horse2755]

Does the fan for a swamp cooler go in front or behind of the water mat.I have mine behind and it works but only near the cooler. Any suggestions?

[ThirdDayOrchids]

Hello
you dont want to use the window ac.it will take all humidity out of the air and you will be fighting to add enough to compensate for the loss.you will lose alot of effic. and operating costs are high.supply tempatures out of an ac in 100 degree weather can be as low as 42 degrees and rarely higher than 50,a bit chilly.if you live in a dry cliamate evaprotive/swamp coolers are an exellent choice as they add humidity(with no other type of humidification 50-55 percent)and can lower temps up to 30 degrees move an constant large amount of fresh air into a green house.sa temps are around the low 70s.much more orchid friendly.a 4500 cfm evap cooler will cool up to 1500 sq. feet with a 10 foot celing.operation costs are low on high equivelent to a few large box fans.you can even buy a couple shop coolers and operate them inside the greenhouse and bring humidity up into the 80 percent range.there a few tricks to venting evaps to obtain the best results so if you want to know more just let me know.I belive the foggers and misters are supplements to cooling and adding humidification.if you set your green house on a bed of four to six inches of gravel you can spray the floor in the morning and it acts like a humidifer adding humidity all day.evaps will lose a little cooling ability the more humid it gets outside but they will also add more humidity in the green house.they will work great for a greenhouse even if the outside humidity level is in the 50s.
jason