I got my large greenhouse, 8 x 16' free from a neighbor who had it sitting doing nothing for years. Probably a couple thousand new. For the new ones im thinking of using a simple 3/4" PVC sch 40 pipe frame and covering with a non-clear plastic between 6 - 10mil thickness and replace the plastic twice a year.
Most of the plastic film sold as "clear" is not clear and will work for obstructing what's inside but still allow the sun to work it's magic.
I've just be thinking about the new greenhouses the past few weeks and haven't put any design ideas on paper as yet but this is how I'm wired, I get an idea, I think about it over a few days/weeks, start talking with others about my idea and steal anyone else's ideas that fit and then measure the area and write it all out with drawings. I usually think about it for another few days/weeks before I actually do it. Ive found I build a lot better and longer lasting things when I take my time and work out any problems in my head first.
I built this one
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Over 10 years ago. I use to re-wrap it twice a year as the sun destroys the plastic within 8 months or so. That tree next to it is now leaning into it by about 2 feet so I need to cut the tree down. But the new ones will be open on the ends (I don't need doors) and instead of an A frame I plan on 5.5' sides with one rail 7' high down the middle. Hard to explain and easier to see once I draw it out.
There's a wealth of ideas on diy greenhouses online. Take some time and look around. That's what I did before designing and building this one
