A properly installed Radiant Barrier can reflect 97% of the Radiant Heat that enters the Attic. When Radiant Barrier is installed on the attic floor, the effectiveness can be reduced dramatically overtime due to dust. When Radiant Barrier is installed on the Rafters the attic can be used safely for storage, while at the same time the natural ventilation of the attic wind washes the Radiant Barrier keeping the dust off and maintaining its reflective properties.