Reflective Foil

Also called a radiant barrier, reflective foil is shiny foil-faced kraft paper, plastic film, polyethylene bubbles, and cardboard, designed to reflect radiant heat away from a space. It is most often used in an attic in hot climates because in summer; the roof is the part of the building that receives the most radiant heat from the sun.

Reflective foil only works if it has an air gap between it and the heat source. This gap could be half an inch or more, as long as the foil is not directly in contact with the hot surface. Note that the foil will increase the temperature of your roof as it keeps the attic less warm.

In a hot climate in summer, radiant heat from a hot roof is reflected away from the cooled interior by reflective foil, reducing the air conditioning bill. Reflective foil is fairly easy to install, even as a do-it-yourself project, if you have the right space for it. It does not reduce conductive heat transfer.

Reflecting radiant energy can be powerful! The Olympic flame is traditionally lit by placing the torch in front of a parabolic reflector that focuses radiant energy from the sun. The focal point of the reflector becomes hot enough to ignite the fuel.