Loose-Fill and Blown-In Insulation

Energy Star

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 materials used for loose-fill insulation include cellulose, fiberglass, and mineral (rock or slag) wool. All of these materials are produced using recycled waste materials. Cellulose is primarily made from recycled newsprint. Most fiberglass products contain 40% to 60% recycled glass. Mineral wool is usually produced from 75% post-industrial recycled content. The table below compares these three materials.

Recommended Specifications by Loose-Fill Insulation Material

Density in lb/ft3 (kg/m3) 1.5–2.0 (24–36) 0.5–1.0 (10–14) 1.7 (27)
Weight at R-38 in lb/ft2 (kg/m2) 1.25–2.0 (6–10) 0.5–1.2 (3–6) 1.6–1.8 (8–9)




For Attic Applications

OK for 1/2″ drywall, 24″ on center? No Yes No
OK for 1/2″ drywall, 16″ on center? Yes Yes Yes
OK for 5/8″ drywall, 24″ on center? Yes Yes Yes





Some less common loose-fill insulation materials include polystyrene beads and vermiculite and perlite. 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. Polystyrene beads, vermiculite, and perlite are typically poured.

The Federal Trade Commission has issued the “Trade Regulation Rule Concerning the Labeling and Advertising of Home Insulation” (16 CFR Part 460). The Commission issued the R-value Rule to prohibit, on an industry-wide basis, specific unfair or deceptive acts or practices. The Rule requires that manufacturers and others who sell home insulation determine and disclose each products’ R-value and related information (e.g., thickness, coverage area per package) on package labels and manufacturers’ fact sheets. R-value ratings vary among different types and forms of home insulations and among products of the same type and form.

. For loose-fill insulation, each manufacturer must determine the R-value of its product at settled density and create coverage charts showing the minimum settled thickness, minimum weight per square foot, and coverage area per bag for various total R-values.

This is because as the installed thickness of loose-fill insulation increases, its settled density also increases due to compression of the insulation under its own weight.  Thus, the R-value of loose-fill insulation does not change proportionately with thickness. The manufacturers’ coverage charts specify the bags of insulation needed per square foot of coverage area; the maximum coverage area for one bag of insulation; the minimum weight per square foot of the installed insulation; and the initial and settled thickness of the installed insulation needed to achieve a particular R-value.