The recommended R-value for an attic varies depending on the climate zone where you live. The United States Department of Energy has created a map that divides the country into eight zones, each with its own recommended R-value for your home, including values for both an uninsulated attic and standard flooring. The absolute minimum for attic insulation R-values across the country is R-30, with upper recommended ranges between R-49 and R-60 for zones 1 through 3. Zone 4 has a minimum of R-38, while colder climates in zones 5 through 8 require at least R-49.