For the last several years I've been contemplating building a greenhouse, not merely to extend the growing season, but also, like you, to grow vegetables around the calendar year. I've collected a number of pieces of mismatched glass panes, and last year helped my neighbor replace a number of dual-pane pieces he had in his livingroom that had lost their seal. He let me have the old ones, which I then separated. I also acquired a good supply of lumber, free for the taking, and stored that until I worked out the design of the greenhouse I wanted to use. I dug trenches where the walls were to be installed, and using large blocks of styrofoam scavenged from a hot tub cover, insulated under the walls by placing the styrofoam pieces into the trenches. in the middle of the greenhouse floor, I shoveled a hole large enough to lay 2 55 gallon drums, which were then plumbed in series and out under the rear wall of the greenhouse to a location where the solar concentrator will heat water that will be pumped into the drums for radiant floor heat. The amount of electricity required to move the concentrator to follow the sun and the small 12 volt sump pump for circulating the water will be minimal.
The dimensions of the greenhouse are 12' x 12', a size determined by the size of the glass panes I was given. They are tempered glass, and I can't do anything about their size with the tools I have. (It can't be cut by normal glass cutting techniques) I had considered using SunTuff, but the price of it was well out of my range. The solar concentrator is a 10' satellite dish, with 4" square mirrors glued to the surface. the "boiler" at the focus is a small "reconstructed" pressure tank that is mounted on a 1/2" pipe measured to the length of the focal distance from the center of the concentrator. The majority of the tracking is done with the linear actuator that was already a part of the satellite dish. Additional electronics that observe the sky and a comparator that moves the actuator according to the brightness level falling upon the 2 sensors keeps the dish aligned with the sun as it moves across the sky. Because I'm using single pane glass, I do lose a lot of heat at night, but I am building insulating panels from corrugated cardboard (laminated at 90 degrees to each other) for stability, a layer of fiberglass insulation, and wrapped in plastic to hold it together. magnets embedded in the cardboard pieces align with screw heads in the greenhouse framing, such that the panels stay in place when set, but are also easily removed when the night is over. It's not automatic, but since I am hoping to spend next winter living in the greenhouse, that's not an issue. It will be like opening the curtains on a house in the morning. As I near the completion of the entire system, (including composting in the air intake vent to provide additional CO2 for the plants) I find that I've spent less than $300 for all of it. It has taken some time to find the materials I need, but by keeping an eye on what other people are willing to throw away well before it deserves to be, (and having plenty of barn space to store such materials in) I've been able to get most of the materials for the taking. In fact, a friend came by the other day, and picked up the rest of the glass I had collected and hadn't used for a larger greenhouse he's wanting to build to provide fresh vegetables for his family throughout the year. The Rodale Press published book "The Solar Greenhouse Book" has provided me with plenty of ideas and experiences of others who have had similar desires. I recommend it. (I found my copy at the local thrift store for a dollar) I wish you all the best in your project. I thoroughly enjoy working in my greenhouse on a chilly windy morning and absorbing the sun and humidity that it provides for me once the sun is shining into it. I'm not nearly as far north as you are, I live in N Georgia, but I am in a mountainous area, and we do get winter here too. Well, I'm off to dig through my neighbor's plumbing parts, just a few connections, and I'll be pumping solar heat under my greenhouse floors in the next day or so! doug swanson Dan Beukelman wrote: > Hello All, > > I have read your posts for several years, but have not ever posted - > lurking in the shadows I guess. > > > > I am wondering if anyone out there has any thoughts/experience with > production agriculture from a greenhouse/hothouse structure. I live in > South Dakota and have been thinking that with energy efficient glass and the > right setup that growing fresh vegetables likes tomatoes year around might > be possible (I say this with a wind chill today near 0 fahrenheit). I have > read that many of the US tomato supply is grown in Canada, which is colder > than us, our area is dominated by grain farming - but I think that local > foods stores would go nuts over a locally grown garden type tomato in the > Wintertime. The construction costs of a very efficient greenhouse should be > able to be covered by the profit from selling a well growing tomato crop, > but the profits go out the window if you have the heat much. All of the > greenhouses I know of around here use plastic coverings and that is only > useful for extending the growing season a little bit on both ends. I am > thinking of keeping growth all year or nearly all year. > > > > Any thoughts? > > Dan > -- Bad politicians give the other percent a bad reputation * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Contentment comes not from having more, but from wanting less. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * All generalizations are false. 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