A polytunnel (hoop) greenhouse like this would be faster and easier to build than a dome. This particular polytunnel design is low cost, strong and easy to build. A greenhouse this size would provide more than enough fruit and vegetables for one family. Instead of bending galvanized pipe for the hoop sections, consider using gray plastic pipe or electrical conduit (polybutylene). I’m not sure how durable it is, but I have seen it used on hoop houses and it would be much easier to use.

Tips:
– use recycled galvanized fence posts for vertical pieces
– save up for commercial grade greenhouse plastic that can last years or even a decade or more
– paint or tape the top of the pipe to prevent overheating and adverse chemical reactions between the pipe and plastic sheeting
– use large enough doors at each end so wheelbarrows can pass through
– consider adding fencing or mesh along the lower 3’ or so to prevent damage from dogs and kids
– hoop greenhouses can be recessed into the ground in low rainfall areas, although you’d want to grade the site to reduce risk of flooding
– provide adequate ventilation, possibly including temperature controlled fans, vents and screen doors
– consider drip irrigation or sprinkler systems to automate watering

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Integrating Shelter, Food, Water and Sense of Place
DIY $200 Homemade Greenhouse
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Comments

High Tunnel Greenhouse Construction — 4 Comments

  1. I used a hooped tunnel for several years. On the plus side, it allowed protection from predators for the plants, and extended the growing season.

    With a hooped design, the best practise is to adopt the permaculture system of layered growth, based around the middle of the tunnel. Legumes and vines as the top foliage, tomatoes as the next layer, tall-growing root crops then shorter ones at the base. Shorter-growing crops towards the sides of the tunnel.

    Only on a huge tunnel would you want to irrigate. Mine was 13 metres long and 2 metres tall. I used mulch, and just watered directly onto the plant roots twice a day. That was 16 gallons of water per day for a fully-stocked tunnel.

    Some crops don’t do as well in a tunnel as they do outside. Brassicas are murdered in a tunnel, because their predators such as cabbage-white butterflies are captive in the tunnel.

    Insects such as bees fly up towards the sun, so get trapped in the roof of the tunnel, trying to find a way out. I also found that a hoop is a limitation in design, because of the restricted height towards the sides, both for working and for plants growing. With plastic sheeting, condensation is also a problem. In the autumn, mildew was a problem, and I had to clear the tunnel and restock the next spring. I sited the tunnel so that an area of trees shaded the tunnel at the hottest part of the day. My plastic lasted 8 years.

    If I had another tunnel, I’d go for one with square sides not a hoop. I’d also go for a fine mesh and not plastic sheet, to let the air circulate, let the condensation out and let the insects out at the roof.

    By all means consider the positives as you have done in your article, but you need to be aware of the limitations too, as I describe above.

  2. One of the most inventive hoop house style green houses I have ever seen was one built by a youth for a 7th-8th grade science fair. (Sorry, I wish I could tell you the kid’s name, but there’s no way for me to remember.)

    He took scrap wood salvaged from somewhere. As I recall it may have been something he took out of a dumpster somewhere, but I’m not certain. He used the fairly small lengths to build hoops that were almost like lightweight roof trusses. Then he used a simple string compass and a jigsaw to cut the top chord to round over any corners or sharp edges. Then probably used a belt sander or something to smooth it all out.

    Extremely cheap hoops… as in almost free. The trade off is that it takes more time to build them, but if you have the time and little money, the trade is probably worth it.

    Of course, used pallets would be a good alternative to do the same thing.
    Or hoops made from saplings.

    Where the kid did something ingenious was to collect clear plastic bags. He got help from family, friends, and I think he enlisted help from a local business that received merchandise wrapped in plastic.

    Then the kid took all the CLEAR plastic bags and used a household iron to fuse the clear plastic bags together to make a big sheet of plastic to cover the hoop house. This is a very common technique used by crafters making various projects. Lots of videos on YouTube describe the process, but they often used various color bags to make designs. For a hoop house, it would be important to use clear plastic for obvious reasons.
    Here is one such video, but there are literally hundreds of others out there.

    http://www.youtube.com/watch?v=PCLXP5BvECI

    Using such techniques and materials it is possible for most anyone to invest a lot of tedious work to build a hoop house greenhouse for trivial expense, even free.

    It may not be the sexiest or the most elegant looking greenhouse, but if someone is extremely short on funds and has the time, it may be a practical option. It certainly can be made to work well if someone does good work.

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