Fiberglass Insulation


Blanket insulation—the most common and widely-used type of insulation comes in the form of batts or rolls, consisting of flexible fibers. The most common of these is fiberglass. You can also find bats and rolls made form mineral (rock and slag), wool, plastic fibers, and natural fibers, such as cotton and sheep’s wool.

Batts and rolls are available in widths suited to standard spacing of wall studs, attic trusses or rattlers, and floor joists: 2 inch x 4 inch walls can hold R-13 or R-15 batts; 2 inch x 6 inch walls can use R-19 or R-21 products. Continuous rolls can be hand cut and trimmed to fit. They are available with or without facings. Manufacturers often attach a facing (such as kraft paper, foil-kraft paper, or vinyl) to act as barriers to vapor and air. Batts with a special flame-resistant facing are available in various widths for basement walls and other places where the insulation will be left exposed. A facing also helps facilitate fastening during installation.

Standard fiberglass blankets and batts have a thermal resistance or R-value between R-2.9 and R-3.8 per inch of thickness. High-performance (medium-density and high-density) fiberglass blankets and batts have R-values between R-3.7 and R-4.3 per inch of thickness.

Loose-Fill and Blown-In Insulation

Loose-fill insulation consists of small particles of fiber, foam, or other materials. These small particles form an insulation material that can conform to any space without disturbing structures or finishes. This ability to conform makes loose-fill insulation well-suited for retrofits and locations where it would be difficult to install other types of insulation.

The most common types of material used for loose-fill insulation include cellulose, fiberglass, and mineral (rock slag or wool). All of these materials are produced using recycled waste materials. Cellulose is primarily made from recycled newsprint. Most fiberglass contains 20% to 30% recycled glass. Mineral wools is usually produced from 75% post-industrial recycled content.

Loose fill insulation can be installed in either enclosed cavities such as walls, or unenclosed spaces, such as attics. Cellulose, fiberglass, and rock wool are typically blown in by experienced installers skilled at achieving the correct density and R-values.