@MoonShadows, I too was thinking about polycarbonate twinwall for the same reasons you brought up, not so much film.
In one of the classes at the Farmer Training Program at UVM that I took in 2015 I was exposed to growing winter green in a hoop house in Vermont, you'd be surprised about how much you can grow without heat. Yes at some point crops do freeze, but not for as long as if they were outdoors, so when they though out you can harvest again
