How can I determine the R-value of my attic insulation?

– Anita

Hi Anita,

The R-value of insulation is a measure of how well it reduces the flow of heat and cold into and out of your house. The higher the R-value, per inch of thickness, the better job the insulation will do when you heat or cool your home.

While you can’t have too much insulation, older homes often don’t have enough. To determine the R-value of the insulation in your attic, you need to know the R-value of the type of insulation in your home and the thickness of the insulation.

R-Value of Insulation by Type

Here are the R-values per inch of the most common types of insulation:

  • Fiberglass (blown): 2.2 – 2.9
  • Fiberglass (batts): 2.9 – 3.8
  • Cellulose (blown): 3.1 – 3.8
  • Rock Wool (loose): 2.2 – 3.3
  • Foam (sprayed): 3.6 – 8.2

As you can see, there’s some variation in R-value depending on the particular type and brand of products used. Depending on where you live, it’s recommended that attics have a minimum R-value of R-30 in warm climates to R-60 in cold climates.

By dividing the recommended R-value for your area by the R-value of your particular type of insulation, you find that an attic should have on average:

  • Fiberglass (blown): 14” – 18”
  • Fiberglass (batts): 11” – 14”
  • Cellulose (blown): 11” – 13”
  • Rock Wool (loose): 12” – 18”
  • Foam (sprayed): 5” – 11”
  • Fiberglass (blown): 17” – 22”
  • Fiberglass (batts): 13” – 17”
  • Cellulose (blown): 13” – 16”
  • Rock Wool (loose): 15” – 22”
  • Foam (sprayed): 6” – 14”
  • Fiberglass (blown): 19” – 25”
  • Fiberglass (batts): 14” – 19”
  • Cellulose (blown): 14” – 18”
  • Rock Wool (loose): 17” – 25”
  • Foam (sprayed): 7” – 15”

To find the R-value of the existing insulation in your attic, multiply the number of inches of insulation by the R-value for your particular type.

For more detailed information on insulation in your part of the country and recommended insulation R-value for attics, walls, and floors; go to the Energy Savers Insulation page on the U.S. Department of Energy website.

Good luck with your project,

Further Information

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Danny Lipford


Danny Lipford is a home improvement expert and television personality who started his remodeling business, Lipford Construction, at the age of 21 in Mobile, Alabama. He gained national recognition as the host of the nationally syndicated television show, Today's Homeowner with Danny Lipford, which started as a small cable show in Mobile. Danny's expertise in home improvement has also led him to be a contributor to popular magazines and websites and the go-to source for advice on everything related to the home. He has made over 200 national television appearances and served as the home improvement expert for CBS's The Early Show and The Weather Channel for over a decade. Danny is also the founder of 3 Echoes Content Studio,, and Checking In With Chelsea, a décor and lifestyle blog.

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