I assume y'all have seen the radiant heat barriers that are sold in our parts catalogs for $60+ for 2'x4' piece. I'm planning on putting a barrier on the floor as well as the roof before installing a new headliner to reduce the sun's radiant heat in the summer. Is there a more affordable source for this application or a way to make a radiant mat myself. I know the barrier is simply aluminum foil. Has anyone done this ?