Loose Fill Insulation

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Loose Fill Insulation
Written by Elizabeth Wood
Editor In Chief, United Home Improvement

What is loose-fill insulation? Loose-fill insulation, also called "blown-in" insulation, is usually made from cellulose, fiberglass, or rock wool. It is generally used in new constructions and in older existing homes, typically in hard-to-reach areas. If properly installed, loose-fill insulation can offer more complete cavity coverage than other forms of insulation, because the fibers can fill around wires, piping, and other obstacles. Special equipment is used to fill building cavities with the small fluffy particles in which loose-fill insulation is broken down into.

• Cellulose Loose-fill Insulation: Made from recycled wood fiber, primarily newspaper, (newsprint and boxes). The fibers of cellulose insulation are much finer than fiberglass. Takes on liquid-like properties that let it flow into cavities and around obstructions. Unlike fiberglass and rock wool, cellulose completely fills walls and seals every crack and seam. Requires less energy to produce. It is inexpensive, nontoxic, safe from fires, environmentally friendly, effective, and highly energy efficient.

• Fiberglass Loose-fill Insulation: Made using sand and recycled glass cullet. The glass cullet is usually melted in high-temperature gas furnaces. This is the most commonly used insulation material. Also, it outperforms most other materials in R-Values.

• Rock Wool (or slag wool) Loose-fill Insulation: Made from blast furnace slag that is a byproduct of steel production. By-products are sometimes recovered from landfills and other materials that would otherwise be wasted.

Primary Applications

Loose-fill insulation is a wonderful way to insulate hard to reach areas including enclosed cavities such as walls or unenclosed spaces such as attics. Areas with irregular shapes and obstructions, such as plumbing stacks, can easily be insulated with loose-fill. Loose-fill is one of the few insulating materials that can be installed without disturbing existing fixtures. However, new constructions tend to use other forms of insulation because special equipment isn't needed for installment.

Insulation Capacity:

Insulation is determined by its R-value. R-value measures thermal resistance. It is important to know that the thicker the insulation is, the higher the R-value. However, R-value is also determined by material and weight. Keep in mind, certain loose-fill insulations installed will lose some of their installed R-value over time because of settling.

Before You Install Insulation

Poor insulation and air leakage are the top two reasons for energy waste. Even the newest of homes can benefit from insulation. Areas that require major insulation attention include attics, basement walls and ceilings, unheated floor spaces, exterior walls and crawl spaces. Before you decide to insulate these areas, certain elements must be carefully examined.

Insulation will not be as effective until you control all of your homes air leaks. Many of these leaks exist within the attic. However, an air leak can exist in any opening between your walls and floors. A professional insulation contractor can assist you in locating some of these hard to find air leaks. Ventilation is another important factor to consider before insulating. Ventilation is essential because it relates to moisture control and indoor air pollution. Keep these aspects in mind before you begin to install.

In addition, vapor retarders and air retarders are also recommended during insulation installments. A vapor retarder is a membrane which is placed between the insulation and the roof deck to retard water vapor in the building from entering the insulation and condensing into liquid water. When adding insulation to a ceiling structure check to see it you currently have vapor retarders installed. If not, consult an insulation manufacturer and your building code official for recommendations on where to place a vapor retarder.

Air retarders reduce energy loss by controlling air flow and preventing heated or air-conditioned air from escaping through the building shell. It also blocks drafts of hot or cold outside air. These drafts are responsible for reducing your home's comfort and heating or cooling efficiency.


Generally, loose-fill insulation is cheaper than batts or blankets. The cost also depends on the material selected and the R-value. On average, loose-fill insulation is about 1.2 cents (installed) per square foot for cellulose and rock wool, and 1.3 cents (installed) per square foot for fiberglass.


Insulation, particularly fiberglass, can be harmful if is breathed in and may irritate skin. For these reasons it is important to use rubber gloves, wear loose long-sleeved shirts and seal gaps between shirts and gloves. All skin must be covered! This especially includes your face and eyes. Make sure to wear a particle mask and something over your head. Also, if you are working in the attic, be careful not to fall through dry wall. Placing plywood planks across the floor will assist you in moving around more smoothly.

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