Radiant barriers are reflective to help reduce summer heat gain and winter heat loss, and hence to reduce building heating and cooling energy usage. The potential benefit of attic radiant barriers is primarily in reducing air-conditioning cooling loads in warm or hot climates. Radiant barriers attic insulation was originally used and were created by NASA! To learn more about the origins of this type of insulation, click here 

Attics:

Most  heat issues that have to do with thermal loss and gain in a home is through the roof and attic areas. To enjoy real comfortability and energy savings, a complete insulation system for an attic/roof should include a reflective, thermal insulation (high R value) coupled with a radiant heat barrier.