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I’m in the research stage of building a large 32′ x 72′ greenhouse – Any insight would be wonderful

ballziez | Posted in Green Building Techniques on

So I am thinking about building a very large greenhouse. I need some insight as to where I might run into issues as I am by no means a master carpenter.

I guess I should start with my credentials here so you guys have a general idea of my abilities. i have worked in a large variety of industries, including flooring, log cabin restoration, framing, painting, electrical and plumbing, fine woodworking. the only places i lack experience is with HVAC.

My goal is to build about a 2000 sq. ft. greenhouse this summer with the dimensions of 32 x 72. with 6-8 foot high sidewalls. (the first 2-3 feet will be brick or something besides just the polycarbonate.

This will be my first solo project (its on private property so I wont have any issues with coding and such) and my land is already zoned commercial-agriculture so municipalities wont be a problem (im in a farm town)

My goal is to be able to produce 3-4 crops per year (in Michigan) which can be challenging because of the changing seasons.

enough about the plan though,
like i stated earlier i want to be able to build the greenhouse by myself (with the help of friends of course) and i am at sort or a cross roads with what materials to use.

for the frame- Wood is expensive (relatively), and is a pain in the butt to take care of. on the other hand, a wood frame is easy to build and doesn’t require any special tools or skills.

Steel seems to be the best option but i have never used the stuff in my life, and the only thing i have been able to find online is kids for around20k (and all i need is skeleton!) any sources for a good metal alternative would be great.

It should be noted i do not want to do a hoop style house, my greenhouse will operate 24/7./

the only other viable option for a frame is aluminum. The problems here is mainly price, and theres no goo way to customize options without breaking the bank.

I plan on using 8mm thick double corrugated polycarbonate plastic on the outside because it seems to be the happiest medium between performance and looks (this greenhouse will be the face of my business. If any one knows cheap links for the polycarbonate panels as well (like <1.5/sq ft) thatd be appreciated. Thanks so much in advanced as this is my first post and i am sorry if i broke ant etiquette

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  1. GBA Editor
    Martin Holladay | | #1

    I don't think that you should re-invent the wheel. You should purchase a commercial greenhouse. Plenty of manufacturers produce these.

    There are lots of considerations here: the crops you plan to grow, the temperature ranges that your crops can tolerate, and whether or not you need to justify your capital investment by a financial analysis that includes your expected revenue.

    Commercial greenhouse manufacturers can provide the equipment you need, including the ventilating equipment that will keep your plants alive in hot weather, and the heating equipment that will keep your plants alive in cold weather.

  2. Expert Member
    Michael Maines | | #2

    George, if you are considering year-round production in a cold climate like yours, if you haven't already, you need to read Eliot Coleman's books: He has been researching and successfully implementing low-energy, year-round production on the coast of Maine for many years. His "New Organic Grower" was his first major book and is full of great tips, and the others go further into the details of cold-season production.

    His wife, Barbara Damrosch, has her own seminal book at the same site, an excellent primer on all things related to gardening.

    The gist is, use galvanized steel pipe. You can bend your own ( but not at the scale you are looking at. I have a lot of farmer friends and relatives here in Maine and they generally use something like this for a high tunnel (unheated "greenhouse"):;ft_high_tunnels_cold_frames;pg103108_106352.html. You can get creative on the end walls if you want, but you will find it hard to beat the price for the basic frame.

    If you want to heat your greenhouse/tunnel, you can use a double layer of greenhouse plastic film and inflate the interstitial space, sort of like a double-pane window. The energy for the blower is less expensive than burning propane with a single layer of film. Twin-wall polycarbonate is a great material but the UV-stabilized polyethylene film will be less expensive up front and will last several years, and is better suited to the low-priced tunnel frames. The two sites linked above should have everything you need for greenhouse or high tunnel production. Johnny's is primarily a seed company, and offers a lot of varieties specifically for greenhouse production.

  3. srenia | | #3

    Wood, is a great product to buid with. Wouldn't worry about it. Grew up in a farm with a 3 acrea of shade plants and another 2 acre of full sun plants. The horizontal strutures (support of shade cloth) where normal 2x4 that lasted decades exposed. The greenhouse I would trying to keep the ceiling height down - less to heat during the fall and spring. The brick would be a heat sink - looks nice but wastes energy.

    Some cheaper option like clear plastic with 2 feet tall or whatever maxium height the plant is can work just as good as the big project greenhouses. Temperature fans when needed. Sometimes simpler is better. Later on when the crops give profit then think of more permanent solutions. Most businesses fail because of bad money management, not bad ideas. Think of greenhouse as tool, not a store front. It's main objective is to extend the season. So reality check is that a permanent greenhouse is a want, not a need.

  4. STEPHEN SHEEHY | | #4

    Check out Griffins Greenhouse supply:

    A lot depends on your level of experience. If you've grown for market and just want to expand, you know what you're up against.

    Mike Maines has some good suggestions. If you've never tried to grow commercially, I strongly suggest you start with a hoop house or low tunnel and see if you can a.) grow anything in volume; b.) market it; and c.) make any money.

    A 2000 square foot polycarbonate greenhouse will cost a bundle to build and another bundle to heat. Better plan on a very high value crop.

    Been there, done that, never again.

  5. edithestey | | #5

    I am also in Michigan and looking to do the same thing. Currentlt have a 1700 sq foot foundation I am actually going to build around. I am trying to get my plans together to get my permits to build.

  6. Expert Member
    NICK KEENAN | | #6

    There is a USDA program to give farmers grants to build greenhouses for free, or close to it. Around here the most popular model is this one:

    1. krom | | #14

      My cousin owns a garden center and has several of those style houses. They stand up to weather very well. I've helped them change the pastic, once from age, and once from hail damage.

  7. Expert Member
    NICK KEENAN | | #7

    Under the program farmers are obligated to use it for four years, which is the life expectancy of the plastic cover. After that, they often get rid of them and you can pick up the frames very cheaply.

    1. edithestey | | #12

      Can you tell me what program this is?

      1. Expert Member
  8. Expert Member
    NICK KEENAN | | #8

    I had to do my post in parts because I got "your comment is awaiting moderation" and when that happens they seem to just disappear. There is one more part I'm trying to post.

  9. Expert Member
    NICK KEENAN | | #9

    I want to post about a blog post where a guy describes assembling one that he bought on Craigslist for $1000 but it won't let me. If you google Ebey Farm you can find him.

  10. KauaiBound | | #11

    Have you considered using geothermal and partially burying the greenhouse? Nebraska farmer grows oranges...

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