This 20x48x12(high) hoophouse kit from Farmtek took two days to erect with one helper and two 12 ft ladders. The subsequent photos show the interior hoop houses that enable me to produce a winter salad crop. The seedlings this winter went in a month too late and thus have grown very slowly. The soils in the greenhouse have not frozen deeper than 1/4 inch. With a little supplemental heat even this could have been avoided with better growth resulting. A future retrofit of the structure with a clay-straw north wall to act as heat sink will improve function and yield. I aim to build a chicken coop and sauna as attachments to the clay straw wall and gain heat for the greenhouse from both.
The walk-in interior hoop house is much warmer as it also encloses a 250 gal horse-watering trough which acts as a heat sink. This house is where I've started the first crop of seedlings for the early spring garden. These baby plants will be go into low (2 ft high) exterior hoop houses made with 5 ft x 7 ft rebar mesh arches covered with plastic. Some of these are already in the garden producing lettuce, arugula, tatsoi, and cilantro and have been productive throughout the winter with no additional heat and only one layer of plastic. I've even found a few lettuces with no protection at all still surviving despite a colder winter with temps that dropped below zero.
The soil in which the lettuce was planted, local soils mixed with purchased compost, is only about 4-5 inches on top of cardboard scavenged from a furniture store dumpster 1/4 mile from home. The cardboard effectively kills off most of the grass and weeds underneath it by the time it decomposes.
The soil under the cardboard was very dry and hard but ,with regular watering and the "rain" of condensate from the roof on sunny days, should be much improved by spring, especially with tunneling rodents and worms eating the beetle grubs and rotting organics.
Here's another style of hoophouse made with plastic tubing and cement blocks. Others have used bamboo, pvc pipes, or bent rebar.