unheated greenhouse

Discussion in 'Gardening & Plant Propagation' started by MaKettle, Nov 13, 2006.

  1. MaKettle

    MaKettle Well-Known Member

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    Took me all summer to build up a level area, lay a patio block floor, and erect a very simple aluminum tube framed, plastic covered greenhouse. 8' x 8'. Can hardly wait for spring! Does anyone in zone 5 and colder found a winter use for one? The wind blows through the bottom and sides, so I don't think it will be much of a heat retainer.
     
  2. chicky momma

    chicky momma Well-Known Member

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    Hey makettle,

    We are in zone 5 also, southern lower Michigan. We have a 14'x32' hoophouse. I can use mine as a season extender but not all winter. Not enough light for Dec.-Feb. Also pricey to keep heated. Am told that if I get cold weather stuff (lettuce etc...) early (Oct.) that I can harvest thru Nov. And start things in March. Plan to try it with row covers to help with the cold.

    Also trying heating with passive solar. Have plastic buckets painted black full of water. Will help to hold some of the day time heat and give it off at night. We don't have enough for such a large greenhouse. But seems more feasible for a small one like yours. Good luck and let us know your results. Lisa
     

  3. uncle Will in In.

    uncle Will in In. Well-Known Member Supporter

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    Trying to heat a greenhouse that's covered with a single layer of plastic, is like trying to heat a barn with the doors open. We gain a little time in the spring by putting flats on a bench inside the greenhouse, and making a little dome over the top of the bench. We hang clear plastic over the dome all the way to the floor. We set a little electric heater on the floor under the bench, and set the thermostat on the heater dial where it will shut it's self off when it is warm enough. It don't cost more than an arm and a leg to start the plants we need for our own use. They reccomend bubble wrap to insulate the green house, but we haven't tried it yet.
     
  4. naturewoman

    naturewoman Well-Known Member

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    I was also told to try the black buckets system. If they are lined up on the floor on the side the sun hits, they get warmed up during the day (if you have any sun...not so good here in Oregon) and then give off heat at night. Also, do not have only plastic on the greenhouse. The front third of the greenhouse, facing the sun, needs the clear plastic to let the sun in. the top and far side should be insulated to retain heat. I was advised to use those insulating panels that have a silver reflective surface to direct the sun back into the greenhouse. Also a solar passive floor like dirt or natural stone helps absorb heat during the day. I've noticed here the temperature inside the greenhouse is the same as outside, but I'm not using the above recommendations now. It does help keep frost off plants, but when it hits below freezing long enough, without heat, anything inside is going to freeze. So, for me, it's not a year-round greenhouse...but lets me extend the growing season. Also, here the orchardists have fans blowing when it's below freezing in the spring, because moving air keeps fruit budding on trees from freezing...so a fan blowing in the greenhouse (without heat) might help too.
     
  5. PonderosaQ

    PonderosaQ Well-Known Member Supporter

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    With a house of that size it wouldn't cost the proverbial arm and a leg to cover the outside with a CLEAR solar pool cover. It's much easier to handle and do than to insulate with bubble wrap. The cover lasts for years. I found the temp in my GH was a steady 10 degrees higher than before I covered it that way. It doesn't cut down on the light to any noticeable degree. Do the other things people suggested and you should do fine growing cool crops later in the fall and earlier in the spring. You can find the clear covers at several places on the web.
    PQ
     
  6. mammabooh

    mammabooh Metal melter Supporter

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    My hubby and I put up a 10 x 12 greenhouse this summer and we are enjoying fresh salad greens everyday. I read Eliot Coleman's "Four Season Harvest" and what he says seems to be true...you can't grow much in the winter, but you can harvest it. However, I planted lettuce, spinach, spinach mustard, and mesclun about a week ago and everything came up and is growing nicely.
     
  7. MaKettle

    MaKettle Well-Known Member

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    Thanks for all your suggestions. Am eager to give them all a try!
     
  8. labrat

    labrat Well-Known Member

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    I am not an expert, but while the black bucket system is good; try a 55 gallon barrel painted black, much more water, and as such will be able to radiate heat much longer to get you through the long cold nights of the zone you are speaking about.
     
  9. Cara

    Cara Well-Known Member

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    As far as the wind coming in, can you put a row of haybales around the bottom of the outside? Might help, especially if you can tack the siding to the bales.
     
  10. mdharris68

    mdharris68 Well-Known Member

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    We had good luck putting another hoop 2 feet off of ground (inside our 12 x 24 greenhouse) and covering with another row of plastic. had salad greens frozen in night and morning, and when sun hit greenhouse we pulled back plastic and began to pick fresh greens.
     
  11. silvergirl

    silvergirl Well-Known Member

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    Bales of straw or hay around the bottom edge should help to stop any draft. Also, once you get the draft problem dealt with, I've geard that housing rabbits in the greenhouse allows their body heat and the heat from their composting stool to warm the place quite a bit... I haven't tried this myself, but read about it in a book on extending growing seasons in colder climates.
    silvergirl
     
  12. WisJim

    WisJim Well-Known Member Supporter

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    After getting the greenhouse sealed up to get the drafts taken care of, it may make sense to cover individual plants or rows with a second or even 2 more row covers, such as Remay plus a transparent cover, to retain heat at the plants themselves. This should allow you to overwinter lettuce, spinach, cabbage family plants, carrots, etc., most winters.
     
  13. Zebraman

    Zebraman Well-Known Member

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    Hey Guys;A small hutch of rabbits is a great way of heating a greenhouse.This is why rabbits have big ears-to disappate heat.Also growing things like Asian Vegetables and salads that actually grow better at cooler temperatures.-