Reflective Barriers block
Radiant Heat in both directions
A radiant barrier works by using a highly reflective aluminum surface to bounce radiant heat back toward its source instead of absorbing it.
During summer, the sun heats up the roof deck, which then radiates heat downward across the attic space toward the floor insulation. Placing a radiant barrier under the roof rafters blocks this direct path of radiant heat, keeping the underlying insulation and the overall house cooler.
In the winter, barriers help contain heat trying to warm up the outdoors.