Radiant barriers reflect radiant heat.
Fiberglass attic insulation vs reflective.
The reflectix site provides a great range of information about this and about how it differs from other types of insulation.
The key to using reflectix properly is that you should take a little time to understand how reflective insulation works in the first place.
Remember traditional attic insulation has r value that works to slow conductive heat.
Radiant barriers and reflective systems.
Which is better will depend on the topography of the specific roof you re insulating.
Air migrates from warmer spaces toward colder spaces and insulation is designed to help prevent or at least slow that migration.
Both types of heat are trying to enter your home on a hot summer day.
The sun heats up the roof and then the heat is transferred by radiant heat across the attic space until it hits the attic insulation.
Reflective insulation is significantly thinner than fiberglass insulation.
The radiant barrier resulted in roughly 4 times more savings than the added insulation.