Greenhouse cooling

[cstriker]

I plan on building a small greenhouse that will roughly be 8' x 8' in size. I'm mainly interested in growing Nepenthes. Temps here in Lakeland in the summer are on average 95F during the day and 75F at night. From what I hear lowlanders would have no problem but highlanders would. How would I cool a greenhouse here at night (say to 60F - 65F) for highlanders? From what I've read the humidity is so high here (especially at night) that a swamp cooler would not be effective. What other options do I have? Does anyone grow highland Nepenthes in Florida in a greenhouse?

Chris

 

[CP30]

Be very careful - the temp inside your greenhouse can climb MUCH higher than the outside temp, especially in a smaller greenhouse. I found this out the hard way last spring in southern Louisiana!!

I have since scrapped the greenhouse and simply keep my neps partly shaded outdoors in the spring/summer/fall. The lowlanders are outside most of that time, many of the highlanders came in to a terrarium in the AC. I have read much success with this method - my plants loved it. If you have the heat and humidity naturally, why a greenhouse?

 

[Jason Wong]

Quote[/b] (cstriker @ Dec. 29 2005,8:41)]I plan on building a small greenhouse that will roughly be 8' x 8' in size. I'm mainly interested in growing Nepenthes. Temps here in Lakeland in the summer are on average 95F during the day and 75F at night. From what I hear lowlanders would have no problem but highlanders would. How would I cool a greenhouse here at night (say to 60F - 65F) for highlanders? From what I've read the humidity is so high here (especially at night) that a swamp cooler would not be effective. What other options do I have? Does anyone grow highland Nepenthes in Florida in a greenhouse?

Chris

Air conditioning?

Maybe Trent does, he's in Florida too.

 

[nepenthes gracilis]

I personally wouldn't try any true highlanders. Plants like N. ventricosa, N. maxima, N. ramispina, and hybrids might be ok. Also, keep in mind there are species with both lowland and highland forms, like N. maxima, and N. veitchii, if you may not be able to grow a highland form, you could most certainly aim for a lowland plant of almost the same "look". For your cooling solution, I cannot offer a true sure fire solution as I do not live in Florida and am not aware of an effective and relatively cheap method to cool your enclosure for highland temperatures, without much investment and equipment.

 

[cstriker]

I figure I'd need a greenhouse for winters. While it doesn't snow it does get down into the 30F at night during the winter. This would kill lowlanders from what I've read. I really like the look of lowii and ephippiata and would love to try to grow these.

Chris

 

[nepenthes gracilis]

N. lowii would be a good choice if you could provide days at max 85F nights of high humidity and around at least 55F.

 

[philcula]

cstriker-

As NG has suggested there is no real "cheap" method of cooling your GH at night without the use of an air conditioning unit. But there are some alternatives. First and foremost you must begin with keeping the day temps at a reasonable level. The cooler your days the better your chance of keeping night temps moderated.

The first thing I would start with is shading. Stay away from shade cloth. Most shade cloth is made in dark colors and dark colors attract heat. If you have to use shade cloth it is advised to build a framing system where the panels can be suspended abve the roof a minimum of 8-10 inches. The higher the better. You may also want to consider white washing the glazing...which IMO is the best option. The whiter the outside surface...the cooler the temps will remain since lighter colors reflect heat away. Do not worry about the prospect of decreased light to the plants from the use of white wash as they do not need to be in full sunlight. 50% to 70% shading would still offer your plants plenty of light to grow well seeing as the sun is so intense in your area to begin with.

You will also need a constant supply of fresh air intake and an exhaust system both working simultaneously. It is best to locate the fresh air intake at ground level (on the shadiest end of the GH) and the air exhaust system should be located on the opposite end wall located as close to the roof as possible where the heat accumulates.

You may also want to grow your highland plants as close to the ground in your GH as is possible. This is where the coolest temps will reside. They should also be in the vicinity of the fresh air intake system because at night the air will be cooler here than it will be at the other end of the GH.

If Cliff Dodd was a member here he could be a huge help. He grows many highland Nepenthes in his greenhouses in Florida...but I "think" he uses air conditioning at night. Don't quote me on this though.

If all else fails and you can't cool your system enough you can grow your ultra highlanders under lights in your basement...provided you have a basement and can accomodate an artificial light growing setup.

Best of luck to you and do let us know how you progress with your project and what devices you employ.

Phil

 

[Dyflam]

Basement in Florida... swimming pool.

 

[Tony Paroubek]

Just a quick note. Exhausting the hot air from the greenhouse and replenishing with outside air will rapidly drop your humidity levels. A fogging/misting system would be effective to help maintain your humidity and give some cooling. It is true that it will only help moderately since your ambient air is not very dry but it will help during the day. I wouldn't recommend running fogging/misting at night however. The cooling effect would be minimal and overly wet atmosphere is not healthy for the plants.

You might be best off with a very large chest freezer converted to a grow chamber if your wanting to grow true highland plants. Neps uses one for his ultrahighland N. villosa but it could be adjusted to maintain 50-55 at night just as well.

Tony

 

[cstriker]

Thanks for all the great info. I'm not too worried about humidity in the summer see how it's usually in 90% at night. The winter, however, would be another story. Even here the winter air is dry. I'll let everyone know of my progress. Thanks again!

Chris

 

[Trent]

Hi Chris,
Dustin and Phil offer excellent advice. Cliff uses an ac that runs during the night.
We are using aluminet shade cloth (70 and 60 percent, half and half)over Klerks Cool Lite plastic on the roof of the greenhouse. During the summer, the sides are aluminet only, so the wind can blow thru and keep temps within reason. You will still need to mist during the day in summer to get really awesome looking plants. We have found that wetting down the leaves right at nightfall very beneficial, and by morning they are dry. With our offshore breeze during summer nights, the wetness slowly evaporates and cools the Neps. This allows us to grow some intermediate-highland types, but still, you can forget the lowii and rajah types. Dustin's list was right on. However, we are finding highland veitchii is fairly tolerant of our summer heat, but really prefers the cool nights of winter.

Trent

 

[yoss]

Hi Chris,

For cooling you may use fogging systems like Arizona mist, mist&cool, etc'...
Operate them by a thermostat and try to get an automatic window opener.
In the hot days it'll cool down the greenhouse and also add to the humidity.
Shadecloth is a must anyway.
When I just completed my greenhouse and just put a few neps in it, I accidently kept the windows closed and it was a hot winter day, temperatures reached 54c (129F!), they neps survived well however... but it was just for a couple of hours.

If you want to grow highlanders try to get a cooling unit and drop the temperatues by 10c at night.

Evaporative coolers won't do you any good as you live in a very humid area and simple fans may dry the air too much.

Keep us posted.

 

[philcula]

Quote[/b] (yoss @ Jan. 13 2006,5:01)]you live in a very humid area and simple fans may dry the air too much.

Someone educate me here please. How does blowing very humid air through a greenhouse dry the air out too much seeing as it is very humid to begin with? If the humidity outside is already in the 80-90% range wouldn't the humidity in the GH still be somewhat on the high side still? I understand the principals of evaporation and convection cooling, I have 1800 sq feet of greenhouse myself, but blowing wet air through a wet greenhouse would still result in a wet atmosphere, wouldn't it? And shading the structure would help lower the temps, and lower temps result in higher relative humidity anyways...don't they?

What am I missing?