Which Blown-in Insulation is Best for Attics: Cellulose Vs. Fiberglass

According to the Insulation Institute, approximately 90 percent of homes are under-insulated. And the attic is one of the places in a home that often lacks sufficient insulation. The good news is that a properly insulated attic can knock anywhere from 10 to 50 percent off your heating bill, so this is a great place to start if correcting insulation deficiencies in your home is one of your goals.

A popular option for attic insulation is blown-in insulation. Also known as loose-fill, blown-in insulation is manually blown into cavities within places like an attic with a mechanical blower or hopper that can be rented at a local home improvement store. Insulating an attic with blown-in insulation, regardless of materials, is usually a two-person job; one to move the blower and hose and the other one to focus on applying the insulation.

Blown-in insulation is appealing because it can also be conveniently applied to attic floors to create an added air/heat barrier. There are two popular forms of blown-in insulation:

  • Fiberglass loose-fill
  • Cellulose

Get a better feel for which blown-in option is right for your attic by learning more about these two common loose-fill materials. Below, you’ll discover more details about the unique characteristics of each type of blown-in insulation material.

Cellulose Insulation

A natural wood product, cellulose is a type of insulation material that’s made from recycled materials. These typically include recycled newspapers, cardboard, and an assortment of other wood-based materials. Blown-in cellulose meant to be used in attics and similar places is usually treated with boric acid and other compounds or chemicals to produce desirable qualities such as flame and mold resistance.

R-Value of Cellulose

R-value is an industry standard rating system that measures a material’s ability to “resist” temperature conduction, or the transfer for heat/air. The typical R-value of loose fill cellulose ranges from 3.2 to 3.8 per square inch. The exact R-value of cellulose, or any blown-in insulation, will vary based on the depth of the insulating materials.

Benefits of Cellulose Blown-In Insulation

  • Easily fills in cracks and crevices
  • Provides good protection against fire, mold, and insects
  • Cellulose’s R-value decreases less over time than what’s common with other types of attic insulation
  • It’s considered environmentally friendly since it’s made from natural and recycled materials

Fiberglass Loose-Fill Insulation

Fiberglass loose-fill insulation is similar to regular fiberglass batts or rolls in that it’s made from tiny glass particles. It’s also common for fiberglass loose-fill to be made of recycled fiberglass, which provides an added environmental benefit. Silica sand, limestone, and soda ash are the main raw materials typically used to create fiberglass during the manufacturing process. Discontinuous glass fibers are used to create both fiberglass batts and loose-fill fiberglass. Fibers of this nature are able to resist heat flow and absorb sound.

R-Value of Fiberglass Loose-Fill

Blown-in/loose-fill fiberglass insulation has an R-value that ranges from 3.1 to 3.4 per square inch. If the loose-fill fiberglass is denser or thicker, however, the R-value can increase. This is also true if thicker layers are applied, which may be possible with an attic floor that’s a bit deeper than what’s common with walls or attic ceilings.

Benefits of Fiberglass Loose-Fill Insulation

  • It can fit well into cracks, gaps, and crevices better than what’s possible with fiberglass batts
  • Sound absorption qualities can make your attic quieter, which can be appealing if you plan to use it as a bedroom, office, or other living space
  • It provides good protection against air and moisture infiltration
  • It’s considered one of the most cost-effective insulation material