What is a Radiant Barrier?
Polar-Ply Radiant Barriers are aluminum foil reflective materials that are installed in residential or commercial roofs to increase energy efficiency by reducing solar heat gain. This reduces the radiant heat gain to ducts and insulation located below the radiant barrier. 

Installing a radiant barrier "tent" in an attic space deflects radiated heat from the roof. It blocks the roofs heat from radiating to the ceiling below.  See RB Applications 

How it works.
Radiant energy from the sun penetrates your roof and builds up heat in you attic.  Shingles, insulation and conventional roof sheathing don't stand a chance against this intense heat transfer.  In the summer, attics can reach temperatures of 150-170 degrees and transmit that heat into you home.

Radiant heat makes your home uncomfortably warm and causes your air conditioning to work harder and longer to achieve the desired comfort.

Polar-Ply Radiant Barriers's unique pure aluminum foil sheet prevents 97% of the summer radiant heat from entering your attic, reducing attic temperatures up to 50 degrees.  Living areas and air conditioning ductwork stay cooler so less energy is required to maintain comfort.  As solar heat increases, radiant barriers effectiveness goes up.