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"Cellulose insulation should be a preferred insulation material for environmentally concerned builders and designers."
- Environmental Bldg. News

Insulation is inherently green because it increases the energy efficiency of homes and buildings. But are some insulations "greener" than others? It's worth a look, especially with the strong interest in environmental responsibility.

Performance
Studies have shown that home insulation currently saves 10.41 quadrillions Btu's per year!
However, if one type of insulation is more effective than another, it can help save even more energy (and money). Studies at universities, national laboratories, private research facilities and hundreds of homes and buildings have shown that cellulose is from 20% to 50% more effective than fiberglass Therefore, using the most conservative number of 20%, if cellulose were used in homes instead of fiberglass, there would be an additional savings of 2.1 quadrillion Btu's per year - the equivalent of a 51-day supply of gasoline for the entire U.S.A.

Recycled Content
Insulation can be an excellent, high quality end use for materials that would otherwise be
dumped into landfills. Cellulose and fiberglass insulation have recycled contents varying
from 0% to 85%. Cellulose contains from 75% to 85% post-consumer recycled newsprint
Fiberglass products contain from 0% to 35% pre-consumer recycled glass

Conclusion
Some insulations are definitely greener than others. There are tremendous differences between cellulose and fiberglass. Even individual homeowners can make a significant environmental impact by choosing the most environmentally responsible, highest performance insulation for just one home. Builders, architects, and insulation contractors who influence the choice of insulation for many buildings have the opportunity to make a
profound impact.

Cellulose Insulation
Having a well-insulated building envelope is crucial to creating an environmentally sound building. By minimizing heat transfer through the envelope, energy used to maintain the interior climate is similarly minimized, reducing both utility bills and the environmental costs of fossil fuel use.
Fiberglass batts are the most common materials for insulating walls and ceilings. Cellulose insulation is made from recycled paper that is applied as either loose fill into attics and closed wall cavities or Dry Dense pack into open wall cavities. Due to its recycled content and potentially higher energy and
acoustic performance, cellulose is an environmentally preferable product.

PRODUCT COMPARISONS

Cellulose Insulation

• High Recycled Content
  
• Less Harmful to Installer
  
• Class I Fire Rating
  
• No Formaldehyde-based Binders
  
• Superior Acoustical Properties

Conventional Insulation

• Low Recycled Content
  
• Potentially Harmful to Installer
  
• Class I Fire Rating
  
• Formaldehyde-based Binders
  
• Inferior Acoustical Properties
  

ENVIRONMENTAL ATTRIBUTES

Energy Performance

• Although cellulose insulation’s R-value of roughly 3.7 per inch is similar to high-density fiberglass batts, it has a significant advantage over fiberglass. Because of its method of installation, it seals all cavity spaces very effectively, greatly reducing air infiltration and higher frequency sound
  transmission. The overall R-value of batts, on the other hand, can be significantly lower than its idealized rating due to typically deficient installation. Loose-fill cellulose settles over time, requiring it be installed at its predicted settled density to achieve its rated R-value. Some manufacturers have created “stabilized” products that reduce settling.

Resource Impacts

• Cellulose is generally made from about 80% recycled newsprint and other waste paper products such as cardboard and paperboard, creating a market for materials that would often otherwise end up in landfills. At the end of its useful life, cellulose insulation can, theoretically, be composted.
  

Health Considerations

• Unlike most fiberglass batts, cellulose insulation does not have formaldehyde-based binders that can be harmful to installers and release gas once installed. Fiberglass fibers are friable and can easily become airborne, particularly during installation. These fibers can be inhaled, and some health
  experts claim that this particulate matter is carcinogenic. For fire and pest resistance, up to 20% of cellulose insulation is composed of ammonium sulfate or boric acid, low-toxicity chemical additives. The boric acid additive is much more desirable, as ammonium sulfate can have significant odor problems if not installed precisely to specifications, and some experts claim it is corrosive to copper pipe. Boric acid is also one of the main additives used in cotton batts and infant clothing for fire resistance. While the health risk posed to installers and occupants is lower than fiberglass, chemically sensitive people who may be sensitive to off-gassing from inks may want to order the loose-fill variety, which is made with cardboard rather than newsprint. Cellulose insulation can absorb more moisture than most other types of insulation. If wall cavities are prone to wetting or are not allowed to dry out after wetting, there could be potential for mildew growth. Ensure a well-designed and constructed wall system.
  

FUNCTIONAL CONSIDERATIONS

Cost

• Having cellulose insulation installed can cost anywhere from the same to twice that of fiberglass insulation, depending on the nature of the project. However, insulation material costs are generally a small percentage of the total cost of construction. In addition, the excellent sealing characteristics of cellulose insulation make it a superior, incomparable product to fiberglass. Since insulation should be a one-time installation, ensuring quality workmanship and material is Important as remedying substandard work later will be costly.
  

Installation

• Loose cellulose fibers are blown into building cavities or attics using special pneumatic equipment. Some installers attach netting to the face of open wall and ceiling cavities and blow in Cellulose Insulation loose cellulose. Because loose-fill cellulose settles over time, it must be installed to its predicted settled density to achieve its rated R-value. Cellulose coverage charts compensate for settling in the bag count and material weight columns; ensure your installer follows the manufacturer’s installation requirements. Cellulose can also be damp-sprayed into open wall cavities before the drywall is applied. Make sure the damp sprayed cellulose has less than 25% water content before closing the cavities with drywall; failure to test the moisture level could lead to moisture and mold problems in the future. A professional installer is required for the damp-sprayed or closed-cavity applications. Cellulose insulation can hold moisture, which should not be problematic in walls assemblies that are dry or are able dry out between cycles of water loading. Repeated wetting and drying could, however, cause the borate treatment to leach out and mold to grow.
  

Maintenance

• Any insulation type will have problems if excessive moisture is allowed into the wall cavity. If moisture is entering the wall cavity, the highest building priority should be to eliminate this problem before even considering the insulation. If the wall cavities are kept dry, there should be
  no need for maintenance.
  

Other Data/Comments

• Check with your local building code and or local utility for recommended insulation levels. The Home Energy Saver can be a useful tool in assessing energy efficiency priorities in your house. It is an excellent on-line calculator developed by Lawrence Berkeley National Laboratory that takes data input by users and reports the measures that will likely be most effective in lowering utility bills and reducing your home’s environmental impact. Use it at http://hes.lbl.gov/