My single-story ranch house was built in the 1950s, and the roof used to have insulation along the joists. In a fit of new homebuyer fever I switched to a hot roof with closed cell foam insulation all along the rafters. The company removed most of the former insulation, but I still have a foil barrier, exactly like tin foil, stapled to the sides of the joists.
The foil isn't in the greatest of shape, as its soiled with 70 years of wear and tear: mouse leavings in some areas, spattered spray foam in others, and has holes, rips, and tears in various other places from fans, ducts, lights, and trips over the years.
There's even a part over a staircase where it hides a booby trap pitfall almost straight to the basement (!)
What was the purpose of this foil, and is it still doing its job now that the main insulation is in the rafters? Can I remove it to further clean up after those pesky rodents? Is it something that should be replaced and kept in good shape?