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  1. #1
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    Sep 2018
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    mini split HAVC for small greenhouse?

    Hi,

    I have an 8' x 12' greenhouse with 6mm polycarbonate walls and roof. I'm in Atlanta, GA so winters are fairly mild, but summers are brutal.

    I'd like to be able to cool the greenhouse during the hottest 3-4 months and heat it during the coldest 3-4 months for year-round growing.

    I'm thinking a mini-split would be ideal, possibly 12,000 BTU in size. Has anyone ever heard of heating and cooling a greenhouse like this? I'm not particularly concerned with cost, between the greenhouse and the garden house enclosure that I built, I already have the world's most expensive tomatoes.

    Thanks!!

  2. #2
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    Jul 2013
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    Richmond, VA
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    The only concern I see is very high moisture content from the plants, which would likely lead to mildew/mold growth on the blower wheel and possibly damage the control board too. Maybe someone who has dealt with hydroponics will chime in.

  3. #3
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    Mar 2013
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    Billington Heights, NY
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    Dont do it. It'll rot it fast from plants and fertilizers. VOCs in greenhouses are huge. An evaporative cooler would be better.

  4. #4
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    Thread Starter
    Thanks, humidity has been something I'm concerned about--and Atlanta is already very humid, but I hope someone with more greenhouse experience will know more.....thanks for taking the time to respond.


    Quote Originally Posted by CircusEnvy View Post
    The only concern I see is very high moisture content from the plants, which would likely lead to mildew/mold growth on the blower wheel and possibly damage the control board too. Maybe someone who has dealt with hydroponics will chime in.

  5. #5
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    Mar 2013
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    what are you growing and what are the parameters of the plants you are growing?

  6. #6
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    Mar 2009
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    Mount Holly, NC
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    Temperature controlled openings or fans work well to reduce temps in greenhouses... heating, I would use a radiant floor loop from a small electric water heater
    ...
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  8. #7
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    Mar 2013
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    Quote Originally Posted by vstech View Post
    heating, I would use a radiant floor loop from a small electric water heater
    ...
    That's what we used except on a larger scale with boilers. I was head of 27 acres of greenhouses. Most were inflated plastic or polycarbonate with inflated roofs. ALL had vents and radiant heat. Most had evaporative cooling and backup plastic ducted overhead heaters. Only the ancient ones had rollup sides with overhead heaters only.

    One house had direct-fired warmed potable water for watering the plants.

  9. #8
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    Sep 2018
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    Thread Starter
    I would like to move my potted dwarf citrus trees into the greenhouse for the winter, and grow collards, kale, broccoli, lettuce, carrot and onions.... I REALLY want to have fresh tomatoes year round, but don't think that's feasible.... I've been looking into the smaller oil-filled radiant heaters, which may be enough if I give up on the tomatoes for winter.

    My greenhouse has a solar powered exhaust fan and two automatic roof vent openers, but that's not enough for cooling in the summer--I wonder if evaporative cooling is enough to cool it in the summer. Of course I don't even try to grow anything in there in the summer, but I would like to be able to enter it to get tools and things without melting. I have a digital thermometer that tracks highs and lows and last summer it reached 136 F!

    As you likely have guessed, this is my first year with a greenhouse--though I've gardened all my life.

    Thanks for any and all advice!!

  10. #9
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    Quote Originally Posted by ATLGIRL View Post
    I would like to move my potted dwarf citrus trees into the greenhouse for the winter, and grow collards, kale, broccoli, lettuce, carrot and onions.... I REALLY want to have fresh tomatoes year round, but don't think that's feasible.... I've been looking into the smaller oil-filled radiant heaters, which may be enough if I give up on the tomatoes for winter.

    My greenhouse has a solar powered exhaust fan and two automatic roof vent openers, but that's not enough for cooling in the summer--I wonder if evaporative cooling is enough to cool it in the summer. Of course I don't even try to grow anything in there in the summer, but I would like to be able to enter it to get tools and things without melting. I have a digital thermometer that tracks highs and lows and last summer it reached 136 F!

    As you likely have guessed, this is my first year with a greenhouse--though I've gardened all my life.

    Thanks for any and all advice!!
    Those are the dirty 6 of vegetables that are known to give off VOCs that rot coils. It happens in commercial coolers all the time (think subway restaurants where the front "desk" is a cooler prep table.) They are not mini split or coil friendly.

    Look at these, for example:

    http://www.schaeferventilation.com/p...oling-systems/

    You can get 30-40 degrees of cooling from them.

  11. #10
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    Sep 2018
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    Wow, I had no idea about VOCs in a greenhouse, looks like more research is in order for my heating/cooling. I have found a number of websites that say an evaporative cooler won't cool much here due to the humidity and high heat. Will continue the search. Thanks to all for great input!

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