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Thread: Greenhouse cooling

  1. #9
    Tony Paroubek's Avatar
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    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
    Is that a Nepenthes in your pocket or you just happy to see me?

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    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

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    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

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    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.
    Yossi

  5. #13

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    Quote Originally Posted by [b
    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?

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