What R-value should I put in my attic?

What R-value you should put in your attic depends on your climate zone, energy codes, and whether you are doing new construction or retrofit, but modern energy codes and the Department of Energy recommend higher levels than older homes have. For most of the United States, the recommended attic floor insulation level is R-38 to R-60. In hot climates like climate zones 1 to 3 covering Texas, Florida, and Arizona, R-38 to R-49 is considered sufficient and cost-effective. In mixed climates like zones 4 to 5 covering much of the Midwest and Mid-Atlantic, R-49 is the current code minimum for new homes. In cold northern climates like zones 6 to 8 covering Minnesota, Maine, and Alaska, R-49 to R-60 is recommended to control heating costs and prevent ice dams. If you have less than R-19 currently, adding insulation is almost always highly cost-effective. If you already have R-30, topping up to R-49 still usually pays back within a few years. Beyond R-60, diminishing returns set in, so air sealing attic leaks around pipes, wires, top plates, and can lights is more important than adding more than R-60.