Radiant barrier works by keeping heat out of your attic in summer and keeping heat in during winter. Here's how: Radiant heat transfers from warm to cool. Radiant barrier reflects the transfer of heat across air spaces. For example, the heat we feel when we walk past a wood stove or a space heater is radiant heat. We don't need to actually touch the stove to feel the heat. A radaint barrier placed between you and the stove will reflect the heat back toward the stove. Installing a radiant barrier in your attic space reflects summer heat from entering your attic space and transferring in to your living space. While in winter, heat from the interior of your home rises in to your attic space and does not pass through, but reflects, retaining heat and keeping your living space more comfortable. Because your heating and cooling system doesn't have to run as much to maintain your desiered comfort, this has a significant effect on lower your utility bills.