Without a radiant heat barrier:

The sun radiates heat to the roof, the roof deck, the attic insulation, and to anyone inside the home.

With a radiant heat barrier:

97% of the heat is reflected off the metal roof radiant barrier, preventing heat from radiating into the home

Solar Radiant Heat – How It Works

759 Brattleboro Road, P.O. Box 47, Hinsdale, NH  03451  877.999.5539