Last winter was devastating on the new greenhouse, the Suntuf panels made it through the winter but not so for the flexible vinyl sheeting.
By the end of the winter most of the vinyl panels would be blown out. So this spring, I started striipping the old off and replacing the vinyl with the Suntuf roof panels.
At the very bottom of the greenhouse, I put Smart Siding to fill in the last space, Smart Siding is primed T-111 sheeting, which gives good resistance to the weather.
I am now planning to do the ends the same way.
-- Steve, Carmel, Maine, USA (near Bangor) (Hardiness Zone 5a)