The radiant barrier resulted in roughly 4 times more savings than the added insulation.
Fiberglass attic insulation vs reflective.
The key to using reflectix properly is that you should take a little time to understand how reflective insulation works in the first place.
Which is better will depend on the topography of the specific roof you re insulating.
The reflectix site provides a great range of information about this and about how it differs from other types of insulation.
Radiant barriers reflect radiant heat.
Radiant barriers and reflective systems.
Reflective insulation is significantly thinner than fiberglass insulation.
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.
What is the right insulation for an attic.
Air migrates from warmer spaces toward colder spaces and insulation is designed to help prevent or at least slow that migration.
Next i compared adding an additional r 19 to my existing r 19 level of attic insulation vs installing radiant barrier and the results actually surprised me a little.