Note that one is allowed to grow within a locked, secured greenhouse. However, there are no specifications as to the construction behind such a greenhouse- just that you must be able to lock it.
Whether the interpretation that sheet polyethylene plastic would survive a legal challenge is up in the air. From the
AZDHS website:CU05: Can cultivation be done in a greenhouse?
Cultivation must be done in "an enclosed, locked facility." A greenhouse is included in the definition of "
enclosed, locked facility". However, to meet the definition of "enclosed, locked facility," the greenhouse must be equipped with "locks or other security devices that permit access only by a cardholder" or surrounded by "solid 10-foot walls constructed of metal, concrete, or stone that prevent any viewing of the marijuana plants, with a one-inch thick metal gate."
From this, a PVC frame with polyethylene plastic sheet would do, provided you had a chain with a padlock that secured any sort of door: enclosed, locked. Consult a lawyer; see what they think.
Any greenhouse will be impossible to secure in a fashion that assures the same security as 10' stone walls with inch-thick metal gates; it's ridiculous. Glass will break, polycarbonate can be cut or burned, and fiberglass isn't much more of a challenge either.