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Facts About Thermal Insulation
Thermal insulation has been used to some degree in ceilings and walls of homes for over 100 years. Its widespread acceptance began about 40 years ago with the introduction of whole-house heating and cooling. The oil embargo of the 70's and the rise in energy prices accelerated the acceptance of high levels of insulation in the home to the point where today they are considered normal building practices.

The three most common types of insulation are blanket, blown, and rigid.

Blanket Insulation

  • Comes in rolls or pre-cut lengths (batts)
  • Installs between framing members (studs, joists, etc.)
  • Made from fiberglass
  • Comes with or without a paper backing that serves as a moisture barrier

    Blown Insulation

  • Comes in a loose form
  • Installed in attic spaces by blowing
  • Can be installed in walls and under floors when combined with an adhesive

    Rigid Insulation

  • Comes in sheet form
  • Installed on the outside walls of a structure with nails or glue

    The effectiveness of insulation is measured in R-value. R-value is the term used for describing resistance to heat flow. The higher the R-value, the greater the insulating power of the material.


    • Blown Insulation
    Blanket Insulation

    THICKNESSES REQUIRED TO ATTAIN STANDARD R-VALUES FOR COMMON INSULATING MATERIALS

    BATTS OR BLANKET

    LOOSEFILL (BLOWN OR POURED)
      FIBERGLASS FIBERGLASS CELLULOSE
    R-11 3 1/2" 5 1/4" 3"
    R-13 3 5/8" 6 1/4" 3 1/2"
    R-19 6 1/2" 8 3/4" 5"
    R-30 9" 13" 8"
    R-38 12" 17" 11"

     
    Which Insulation is Best?

    The two main insulating products in use today are fiberglass, made from melted glass, and cellulose made from recycled newspapers. Many insulating companies install both.

    Fiberglass insulation is made by melting glass or sand and then spinning it into fibers, like making cotton candy. The fibers are matted together in a large blanket that is cut into smaller blankets or shredded for blown insulation. About 20 percent of the materials that go in fiberglass insulation are recycled glass and bottles.

    Cellulose insulation is made from ground newsprint, phone books and sometimes a small amount of cardboard. Added chemicals repel bugs and prevent fire. Cellulose is available both loose fill and blown; about 80 percent of its content is from recycled products.

    Does one insulation make your home tighter than another? "Control home air infiltration first by sealing. Cracks in the home's structure, openings around pipes and wires and leaky recessed light fixtures are good places to start," says Walton EMC Member Services Representative David Foster. "Even though wall-blown systems that mix fiberglass or cellulose with adhesive do a good job of stopping air leaks, don't depend totally on them for infiltration control."

    There are differences in cellulose and fiberglass. It takes a greater thickness of blown fiberglass to get the same R-value (a measure of the resistance to heat flow) as blown cellulose. This won't be a factor in places like attics, where there's plenty of room. If space is limited (like in walls or cathedral ceilings), cellulose may be preferred.

    Though cellulose doesn't have to be as thick to reach a desired R-value, it settles more than fiberglass when blown in. When installing, add 20 to 30 percent more cellulose than the thickness you ultimately want.

    What about safety? All loose fill insulation products must meet minimum fire standards set by the Consumer Products Safety Commission. Wear proper safety gear (dust masks or respirators, safety glasses, gloves) during any insulation installation, regardless of the product. Make sure to follow the manufacturer's recommendations.

    The most important step in insulating is to do it. Adding cellulose or fiberglass insulation saves money and make your home more comfortable.

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