Recommended R-Factors for Home Insulation in Arizona


Arizona has some of the hottest weather in the United States, and having adequate insulation in the home protects it from heat gain in intensely hot summers. The state has many micro climates as well where winter lows can go below zero, so adequate insulation for homes in all the life zones in Arizona helps the residents of the state save money on their heating and cooling bills and increase comfort indoors.

Roof Insulation

  • The Environmental Protection Agency certifies homes as Energy Star when they meet specific requirements for energy efficient features, one of which is adequate levels of insulation in the floors, walls, and roofs. Insulation is rated by its ability to resist heat or cold. An insulated roof with an R value of 30 would resist heat for 30 hours, while an R value of 20 would resist heat for 20 hours.

    Under the EPA's zone designations for Arizona, there are four zones in Arizona, each with specific recommendations for the insulation. The R values for ceilings and roofs in the deserts of Arizona (Zone 2, 3, and 4) call for insulation rated from R 30 to R 60. In the colder mountains of Arizona, the recommendations are to have at least an R value of 49 and a maximum of R 60.


  • Wall insulation is as important as roofing insulation and the EPA recommends that homes in the lower deserts in Arizona have a minimum R value of 13 and a maximum of 19. In the higher deserts, the EPA recommends that the R values start at 19 and go to R 25 to 30. In the mountains, the EPA recommends that the walls have wall insulation values starting at R 25 and as high as R 30.


  • The floors of homes in Arizona also protect the building from heat or cold from entering a building. The EPA recommends R values from 13 to 19 in the hottest deserts, from R 19 to R 25 in the higher deserts, and from R 25 to R 30 in the colder mountain regions.

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