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What Is the R-Value of Insulation?

If you think your energy bills are higher than they should be, you could benefit from adding insulation. The most important places for insulation include the attic, wall, crawlspace, floor and ceiling. The goal is to insulate the entire outer envelope of your home to keep the interior more comfortable all year round.

You need to choose insulation that delivers a certain R-value, or heat resistance value, to get the most from your investment. Insulation R-value depends on the material it’s made out of and what form it takes.

R-Value of Different Insulation Materials

Here are some of the most popular insulation choices:

  • Fiberglass insulation comes in batts, rolls, blown-in and rigid forms. Standard fiberglass batts are the most common insulation used in attics and walls because they fit snuggly between joists and studs that are built to code. Standard batts have an R-value of R-2.9 to R-3.8 per inch.
  • Cellulose insulation is a type that is typically blown into place. Cellulose insulation R-value is R-3.2 to R-3.8 per inch.
  • Batt insulation can be made of fiberglass, mineral wool, plastic fibers or natural fibers. You can get high-performance batts rated as high as R-4.3 per inch.
  • Blown-in insulation can be made of cellulose, fiberglass or mineral wool. The R-value depends on the material. Cellulose blown-in insulation R-value is stated above. Fiberglass blown-in R-value is from R-2.2 to R-2.7 per inch.
  • Rigid foam board can be made of polyisocyanurate (polyiso), extruded polystyrene (XPS) or expanded polystyrene (EPS). Rigid foam board insulation isn’t generally used to retrofit existing homes. Rather it’s used by builders to insulate unfinished walls and unvented roofs with an R-value ranging from R-4.6 to R-6.5 per inch.
  • Radiant barriers are reflective surfaces that help direct heat away from the home. They’re most often installed on the underside of the roof, though when installed over existing insulation on the attic floor, radiant barriers can add another R-2 to the insulation’s overall thermal resistance.

Note that these numbers may not specifically apply to your situation. They are general and for informational purposes only.

Southern CA Insulation Installers

Getting the maximum thermal performance from your insulation depends heavily on proper installation. Even if you handle other DIY projects around the house, we recommend a professional, certified installer when it comes to insulation.

Count on OJ Insulation to perform the installation for you. We have helped San Diego and Los Angeles area homeowners re-insulate their homes for over 25 years. Contact us today!

Where should you insulate in your home? Check out our interactive infographic:

Home Insulation

We insulate attics, walls and crawl spaces.

Commercial Insulation

We insulate warehouses, offices, studio spaces & more.

Insulation Removal

Do you need to remove old insulation? We can help.


We work with builders to install fireplaces.

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