Wonder if anyone has made their own.
From a link:
"Insul~Bright consists of hollow, polyester fibers needlepunched through a nonwoven substrate and through a reflective metalized poly film. The needled material is breathable and won’t break down with washing. The hollow fibers resist conduction while the reflective metalized poly film resists radiant energy. The energy, hot or cold, is reflected back to its source."