The easy answer is that there are so many different types of crops. In looking closer however, we see certain types prevailing, in the different temperate regions.
Fabric or film are terms used to describe the same thing. A roll product, sold in running feet by width, it is used commercially in all but the coldest growing regions. Even in the Northeast, the Midwest, robust UV stabilized, often woven coverings offer 10 to 15 years before replacement. When recovering a 96’ long greenhouse, the upset to operations needs to be minimized. Fabric or two ply film with inflation bladder is by far the most cost efficient to purchase and when needed, recover.
Poly-carbonate has been available for some years now. The improvements have been impressive. The ability to stabilize against UV degradation has improved, the ability to meet some tough engineering criteria, has allowed the use of light weight poly-carbonate in places that benefit from the transparency. Nurseries can show off starts, propagation, flowers, through single wall poly carbonate with the clearest transparency with out the cost of tempered glass like in a patio door. Double wall poly carbonate kits, some with pvc frames, some with aluminum frames, some with cedar frames can be found at most big box retailers. They have a place in helping gardeners too. The 12 mil and 20 mil triple wall poly carbonate coverings are best suited for the colder growing regions and specialty exotics, like orchids. The cost and complexity of installation is something to be considered before any grower takes this type of model on. Often it is best to have a builder with experience in poly-carbonate construction assist.
For years the use of 6 0r 10 mil roll plastic has been used by the frugal gardener. Often covering a wooden structure, stapled and lath strapped into place. While in the short run the upfront costs are less, long term it costs more, takes up space in the landfill, and takes this side of forever to breakdown. Until we can see some market for the used plastic, a non-subsidized one, 6 mil or 10 mil will do in a pinch. We don’t recommend it because long term it costs more.