Like a space suit, Radiant Barrier foil insulation reflects the sun’s heat before it can warm up the insulation in your attic. When the insulation stays cooler, your house will too. Just like a Space suit or Thermos bottle, the reflective surface inhibits radiant heat transfer.
Just like wrapping a baked potato in aluminum foil keeps it warm longer by holding in the heat, covering your attic insulation with Radiant Barrier holds the heat in the house.