Can I Use R19 In 2×4 Walls?

Can I Use R19 In 2×4 Walls? Use R-19 or R-21 kraft-faced fiberglass insulation for two-by-six (2×6) walls. This combination ensures that the insulation is neither too loose nor too tightly packed within the walls. Two-by-four (2×4) stud walls with true 4-inch depth. How thick should insulation be for Shed? Shed walls usually are framed