How Thick is R25 insulation?
R25 can be many different thicknesses. It depends on the
insulation product. Styrofoam SM would need to be 5" thick. Pink
fiberglass would need to be about 7" thick. White (beadboard)
styrofoam would need to be about 6.75" thick. Blown in attic
insulaton would need to be about 10" thick.