What JD Said...
Insultex is a PE foam sheet that's been quilted (Stitched) to a polyester scrim (to add strength) It's not a vapor barrier, per se, but it's breathability is very limited.
This stuff will likely leave you sweaty in anything but the driest conditions. . .
That said, it would make a great windblock if used below a UQ or something, just make sure it's loose enough to breathe. . .
"Do or do not, there is no try." -- Yoda