Sorry to threadjack, but I wonder if the plastic would be a suitable backing material to hold garage door insulation in place and make the install look cleaner?
I just bought some fiberglass insulation for my garage door because it was deeply discounted. They make foam board panels that look better, but they don't have as good of an R-value and aren't on sale at the moment.
From reviews, it seems the fiberglass stuff has a tendency to sag over time and look messy.