Which way does the foil face (reflective side) on the AP foil faced insulation need to face?
In most cases it doesn’t matter. Both sides have the same perm rating (0.05 perms). The reflective side will give an increased R-value when used behind an exterior brick veneer. This is called a reflective air space. Sometimes the non-reflective side is installed towards the outside to reduce glare from the sun or to eliminate any concerns about too much heat build up behind vinyl siding.
