My first thought was 'that sounds like something The Mother Earth News
magazine has done, at some point. I started looking in their archives, but they had 100 entries under '
greenhouse' and it wouldn't let me refine the search. If you have the time to search, you may well find some good ideas.
Then I ran across this
greenhouse (photos and all) at GW:
http://forums2.gardenweb.com/forums/load/strucs/msg1022425114142.html?54 There is a guy in the next town north who built a
greenhouse on the south side of his garage using sliding-doors. I think he just had some 2x4s between them. The sides and ends were glass and the slanted roof was, too. The only part that wasn't was the triangle area above the doors on the end.
One thing I had heard: if you make the roof of windows, make sure the roof slopes enough to dump the snow. A foot of wet snow is really heavy, over 300 lbs per square
yard.
And the photos I've seen seem to indicate that using windows that are all the same size and shape look best.
To tell the truth, if I could do it, I would use single-pane tempered glass. I'm pretty sure that sliding doors are tempered glass, and they're pretty big. Some are double-paned... if you removed the edging, would you have two panes without too much work?
And I've read that if you live in cold country where the ground freezes much, you need to insulate the
underground perimeter of the
greenhouse with sheet styrofoam or something.
Some flat-black-painted 55-gal barrels inside at the back would absorb
solar heat and give it off at night.
Some people want a floor (bark, rocks,
concrete slab, etc), but others leave the floor (other than a walkway down the middle) as natural soil, and plant heat-loving things like
tomatoes and gourds right in the ground for the entire growing period. In a bookshop in Olympia, I was talking to a woman who did that, getting them in early and extending the maturing time, and got MASSES of large gourds (that's about the only way you'll get them in western WA).
Don't forget about adjustable ventilation, and that means cross-ventilation. One opening is nothing but a very large
solar oven. ... Where the plants get cooked before they produce, I guess you could say!
Sue