Retirement for the Pink Panther™?

Jan 25, 2012 by

Retiring Panther

by Tim Snyder

7 reasons NOT to insulate with fiberglass

Fiberglass insulation (and its main mascot, the Pink Panther™ trademarked by the Owens Corning Corp.) has dominated the home insulation market for generations. Since its invention by Owens Corning in 1938, fiberglass has been the go-to material for insulating just about any building assembly. Glass fibers have been made into batts, blankets and loose-fill insulation for use in walls, floors, ceilings and attics.

But this long run as the dominant insulation material may be coming to an end. Interest in energy efficiency continues to grow due to rising energy prices and the popularity of “greener” living. As a result, building scientists, insulation contractors and consumers are finding alternative insulation materials that outperform fiberglass in significant ways.

Fiberglass is still less expensive than most other types of home insulation, and will probably retain its price leader status for some time to come. But poor performance compared to other types of insulation shouldn’t be ignored. Whether you’re choosing insulation for a new house or upgrading existing insulation levels to increase interior comfort and decrease utility costs, here are 7 reasons why fiberglass insulation might not be the best choice.

1. Low numbers. The universal measure for insulation is R-value, and fiberglass insulation scores pretty low on the R-value scale when compared to other types of home insulation. For example, a standard 3½-in.-thick fiberglass batt designed to fill a 2×4 wall provides just R-11 of insulation value. Filling the same space with spray polyurethane foam (SPF) achieves R-21.

2. Installation errors. One reason for the popularity of fiberglass insulation has been easy installation. But research by building scientists has shown that it’s nearly impossible to install fiberglass batts perfectly, and installation errors are costly in terms of energy performance. A void (missing insulation) that represents just 5% of the total insulated area for a wall assembly can diminish the wall’s insulating performance by as much as 50%.

3. Mold & moisture problems. Fiberglass insulation (especially batts faced with kraft paper) can absorb and hold moisture. While this won’t degrade the glass fibers, it dramatically diminishes R-value, while also encouraging mold and rot in surrounding building materials. Mold grows easily and abundantly on paper-faced fiberglass batts, and on wood and wallboard in walls that remain damp.

4. Air movement. Fiberglass insulation can slow heat transfer by conduction, but it can’t stop heat transfer by air movement or convection. The numerous gaps, cracks and openings in the “building envelope” allow conditioned inside air to escape (exfiltration) and outside air to enter the building (infiltration). To ensure maximum R-value with fiberglass insulation, these leaks must be sealed in a separate air-sealing step.

5. Bad below grade. Over the years, fiberglass batt insulation was used extensively to insulate framed walls in finished basements and to insulate crawl space ceilings. It is no longer recommended for these uses because of the moisture-related problems explained in #3, above.

6. Stellar competition. Most of the limitations of fiberglass have been overcome by other types of insulation. Closed-cell spray foam and rigid foam are two insulation materials that don’t absorb moisture and are preferred for use in basements and crawl spaces. What’s more, these materials positively seal the spaces they insulate, significantly diminishing energy losses due to air infiltration and exfiltration.

7. Not so green. Yes, all insulation has “green” value because it helps to save energy and reduce our consumption of fossil fuels. But fiberglass insulation isn’t nearly as green as cellulose insulation, the other “fluffy” insulation option. Cellulose insulation contains about 85% recycled content and doesn’t require a lot of energy to manufacture. Fiberglass insulation typically contains 20%-30% recycled glass, and requires furnace temperatures in the 2500degrees F range –a very energy-intensive process.

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1 Comment

  1. Erik Brandstadter

    Poor installations of ANY product goes along with poor performance.

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