Reflective insulation is fabricated from some type of metallic foil, such as aluminum, and backed with plastic film, polyethylene bubbles, cardboard or kraft paper. The product is engineered to stop radiant heat transfer between open spaces. It's similar to radiant barriers but differs in that it includes a radiant barrier plus other insulation materials.
Reflective insulation is usually found between roof rafters, wall studs or floor joists. Its performance and cost-effectiveness over time depend on how the insulation is installed, where it's installed and how much existing insulation might be in a house. The materials reflective insulation is made of will conduct electricity, so hiring a professional to install it is advised.