My ultimate goal is to build something up in the Colorado high country (10,000 feet) and was looking at various options to cover some tillable land as well as to modify the underside of a deck to make it a greenhouse. In one case, a free-standing greenhouse, would have to not only survive snow and wind loading, but also to keep from being run over by free-ranging cattle, deer, elk and possibly a curious bear.
I looked at the Harbor Freight green house but I do not think it is strong enough for this area. A greenhouse built under the deck would be the easiest to protect and would survive the environment. A Quonset hut type of greenhouse with 6 mil plastic sheathing I think would be penetrated by critters. So... some other frame structure using corrugated plexiglass is bubbling to the top of my idea pool, but I would like some way to double-glaze it to improve the isolation and insulation during winter.
Hopefully, you all will give me some good ideas.