In these attic space applications there is an air space below the radiant barrier.
Radiant barrier roof shingles.
Nevertheless a radiant barrier may still help to improve comfort and to reduce the peak air conditioning load.
One common misconception regarding radiant barrier is that the heat reflecting off the radiant barrier back to the roof has the potential to increase the roof temperature and possibly damage the shingles.
A radiant barrier continues to be an excellent solution to block that heat before it enters your living space but many diy homeowners and even some professional installers question whether the radiant barrier reflecting the heat back up can actually make.
However we will do our best to explain why the effect is nominal.
A radiant barrier can be effective with an asphalt shingle roof only when installed inside the attic either to the underside of the roof decking or to the underside of the roof rafters.
As for the metal roof i would install atticfoil radiant barrier below the metal roof.
This can be a little tricky to understand because it seems logical that the roof would get hotter if the radiant barrier below it is reflecting 97 of the radiant heat back through the roof assembly.
Here are instruction on how to install a radiant barrier under a metal roof.
Black asphalt roof shingles absorb over 90 of the radiant heat that strikes them making them easily over 170 degrees on a hot summer day.
Radiant barrier damages roof shingles.