Hillary used to work for some folks who used to own a nursery business. they quit that and had a bunch of greenhouses to get rid of. we hauled off some of the steel water pipe the greenhouses were built out of and have been sanding and grinding off the rust and painting them to build a new and better greenhouse. the pipe is bent into semi-circular hoops sixteen feet in diameter. the glazing will likely be Solexx or, more likely, double or triple wall polycarbonate. it'll be earth-sheltered, as suggested by Mike Oehler. there will be a solar closet for heat on cloudy winter days, and animals for a little more heat and plenty of carbon dioxide and pisshit. a pond to the south will reflect more sunlight to the greenhouse, especially during solar winter. solar vents and perhaps a solar chimney will provide cooling when necessary. a pond inside the greenhouse will keep humidity high, decreasing temperature fluctuations. deciduous vines and trees planted outside will provide a bit of shade to keep things reasonable in the summer. plans will change as the project goes forward and we learn more about what works and doesn't. if the whole thing is reasonably successful, we'll use the experience to build a larger greenhouse in the future.