Everything decomposes faster in the Texas sun except pine needles.
I suspect even real greenhouse film won't last long out there, but I only need it up for a couple of months at a time.
Elliot Coleman suggests this method "moves you 500 miles south" for every layer. I'm assuming this only relates to harsh winter climates.
What's confusing me is that I've read that radiant cooling may remove the heat right away, and that in some tests it ends up actually cooler underneath than ambient. Anecdotal evidence is all over the place, from "30 degrees higher at night" to "a few degrees of protection" to "no difference". And nobody specifies what kind of plastic, they just say "plastic"!
It's an inexpensive experiment, I'm definitely going to try it. Just would like to know where to set my expectations - I'm thinking "a few degrees of protection" is about it.