"...radiant barriers can reduce summer ceiling heat gains by about 16 to 42 percent compared to an attic with the same insulation level and no radiant barrier..."

"Can a reflective radiant barrier, installed over existing bulk insulation, decrease heat loss in homes and commercial structures?"

"There is no reason to believe, or tests to prove otherwise, that radiant barriers will damage shingles...
...The following roofing material manufacturers have confirmed that their respective warranties would not be affected by the application of an attic radiant barrier."

"When the sun heats a roof, it's primarily the sun's radiant energy that makes the roof hot. A large portion of this heat travels by conduction through the roofing materials to the attic side of the roof..."

"Products defined as radiant barriers have surface emittances less than or equal to 0.1 or low radiant heat transfer rates..."